AECL-5703

ATOMIC ENERGY K S S i L'ENERGIE ATOMIQUEOF CANADA LIMITED T S V DU CANADA LIMITEE

PROGRESS REPORT

BIOLOGY and HEALTH PHYSICS DIVISION

October 1 to December 31, 1976

PR-B-112

Chalk River Nuclear Laboratories

Chalk River, Ontario

PREVIOUS REPORTS IN THIS SERIES

AECL-5678 July 1 to September 30, 1976 PR-B-111

AECL-5602 April 1 to June 30, 1976 PR-B-110

AECL-5540 January 1 to March 31, 1976 PR-B-109

AECL-5376 October 1 to December 31, 1975 PR-B-108

ATOMIC ENERGY OF CANADA LIMITEDChalk River Nuclear Laboratories

PROGRESS REPORT

October 1 to December 31, 197 6

Biology and Health Physics Division

PR-B-112

Chalk River, Ontario

AECL-5703

PROGRESS REPORT

October 1 to December 31, 1976

Biology and Health Physics Division

Director - A.M. Marko

Secretary - C.L. Nagy

Machinists - M.I. Gibson

L.G. Hunter

CONTENTS

1. Summary - A.M. Marko 1 - 6

2. Health Physics Branch - G. Cowper 7 - 36

3. Environmental Research Branch - I.L. Ophel 37 - 87

4. Population Research Branch - H.B. Newcombe 89 - 98

5. Biology Branch - D.K. Myers 99 - 133

BIOLOGY AND HEALTH PHYSICS DIVISION SUMMARY

A.M. MARKO

Health Physics

Experiments are being developed to obtain verific-ation of computed leakage spectra from neutron sourcescontained in various absorbers. To this end, hydrogen-filledproportional counters, having different sizes and fillingpressures, have been calibrated with monoenergetic and distrib-uted energy neutron sources. The counters, surrounded byresonance absorbers, silica for the silicon resonance andteflon for the fluorine resonance were placed inside a graphitepile containing a Pu-Be source. Energy calibrations indicatedby resonance absorption were then verified by exposing thesource counters to monoenergetic neutrons provided by aVan de Graaff generator.

New personal dosimeter badges have now been providedfor 2000 users at CRNL* and remaining users will be equippedwithin a few weeks. The previously noted reduction in spuriousreadings with a few hundred users has been sustained. Inparticular, anomalously high readings of skin dose have essent-ially disappeared due to the exclusion of thermolurninescentdirt and dust from the new badge. Arrangements have now beenmade to carry out environmental monitoring with plague mountedTLD's rather than manually controlled single chips. Dosimeterplaques are annealed while being exposed to UV to enhance theirsensitivity. Such dosimeters have an annual fading rate ofonly 6% which is entirely satisfactory for environmentalmonitoring purposes.

A monitor to detect the presence or absence of spentreactor fuel has been developed to suit the safeguards require-ments of the Douglas Point Generating Station. In thisinstrument a linear array of eleven semiconductor diodedetectors measures the radiation from a layer of eleven fuelbundles in a storage tray. An absent or a dummy bundle isindicated by a detector reading which is more than three timesless than that from detectors facing adjacent irradiatedbundles.

A tritium monitoring system for a 3He controlledloop in NRX is being commissioned. It comprises three monitorswhich measure the tritium concentrations in the air exhaust,in the vicinity of the loop control station and in the loopatmosphere itself. Techniques and components developed fortritium monitoring at power reactors have been adapted and

*Chalk River Nuclear Laboratories

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extended for this system.

Work is continuing on the development of an automatictrack scanner to score charged particle damage tracks in alphairradiated cellulose nitrate films. An acceptable image ofan irradiated and etched foil has been produced.

Environmental Research

As part of the research program on the effects andutilization of waste heat, studies are in progress on theoptimal temperatures for maximum growth of selected speciesof green algae. The experiments are designed to assess theeffect of different temperatures, under saturated lightingconditions, on growth and reproduction.

An 80 cm core from the bottom sediment of Perch Lakeis being used to investigate the inter-relationships oforganic matter in the lake and its sediments v;ith °Co, 90Rr,certain stable elements and other chemical properties. Thecore was sectioned into 80 x 1 cm layers for analysis.Ignition loss, total organic carbon, cation exchange capacityand fixation capacity in addition to stable cobalt, strontiumand calcium are being determined for each core segment.

Energy budget and evaporation studies in progress atPerch Lake have been extended to include Maskinonge andUpper Bass Lakes. The object of the enlarged study is torelate turbulent diffusivity in the lakes to wind speed,lake size and water quality. Such information is needed inconnection with studies on the fate of wasts heat dischargedinto water bodies and in the distribution of radioactive andother chemical substances in lakes.

In collaboration with G. Szeicz and L.K. Hendrie,Dept. of Geography,University of Toronto, H new project hasbeen initiated to investigate the water balance of aforested catchment area using tracer techniques. Although primeemphasis is being placed on the radiative exchanges involvedin the snowmelt process and on evapotranspiration during thewarmer months, other relevant factors will also be considered.The experimental site is in aspen-birch-maple forest near thesoutheast side of Perch Lake.

A detailed study of various methods for determiningground water velocity and dispersivity was carried out atCRNL in cooperation with u.F. Pickens, Dept. of Earth Sciences,University of Waterloo. These are the principal factors which

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control the transport of contaminants in ground water. Acomparative study of hydraulic conductivity was performedusing pumping tests, single-well response tests, pointdilution tests and a radioactive tracer (51Cr-EDTA) test,in conjunction with numerical simulation modelling. A newmultiple ground water sampler was developed for the work andproved to be very successful.

Background gamma radiation measurements were carriedout in the restricted area of CRNL and on Highway 17 up to30 km from the village of Chalk River, using a sensitivevehicle-mounted instrument. Surveys of the plant road andthe Port Hope Waste Area bypass road during the fall of 1976,when contaminated soil was being transported by truck, showedno changes in exposure rates over the period of measurement.

D.R. Champ is collaborating with P. Unrau gyBranch) in a study of a novel class of proteins, produced bythe smut fungus (Ustilago), which may possess a controlfunction in DNA repair and in other cellular processes. Theoccurrence of this class of proteins in other organisms isalso being investigated.

Population Research

In the case of radiation-induced cancers it ispossible to obtain data on the magnitude of the social burdenin terms of loss of life expectancy and utilization ofhospital facilities; similar data would be desirable asrelating to genetic disease of kinds lil:ely to be caused byradiation exposure. More specifically, what are required arethe rates of hospital admission, the durations of the staysin hospital, and the rates of death, at various times in thelives of the affected individuals. Such information iscontained in the British Columbia vital and health recordsbeing used for population studies at CRNL, but these recordsmust first be linked into appropriate individual healthhistories before the information can be extracted. During thepast year, the required linked files have been built up, basedon records of births, handicapping conditions, hospitalizations,and deaths, among children born from 1946 onward. These linkedfiles will be used to provide the necessary age specific andcumulative rates of onset of disease, rates of hospitaladmission and utilization, and rates of death.

Biology

Studies on the molecular basis of radiation damageto the DNA, the enzymatic repair of this damage, and the

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consequences of repair for radiation effects on the livingcell have continued.

The yield of double-strand breaks in the DNA ofvarious strains of Micrococcus radiodurans has been measuredunder a variety of conditions and shown to be independentof the radiosensitivity of these strains. The effects ofoxygen on the yield of double-strand breaks were shown todepend upon irradiation conditions and were attributed to rapidradiochemical reactions that occur during the irradiation. Theyield of single-strand breaks has also been measured under avariety of conditions; in order to obtain accurate values,it is essential to minimize repair. Under these conditions,the maximum number of single-strand breaks induced byy-radiation is 25-30 times the number of double-strand breaks.

The significance of recombinational and excisionrepair pathways for the survival of irradiated cells hasbeen studied in three microorganisms. In all three cases,the recombinational pathway appears to play a major role indetermining their sensitivity to y-radiation. In two of thesemicroorganisms, M. radiodurans and Schi zosaccharomyces pombe,the effects of holding the irradiated cells for a period oftime in non-nutritive medium were also explored. Under thesecircumstances, irradiated cells that were still viable at firstdie gradually, owing to an inability to complete recombinationalrepair; this type of cell death does not occur if the recomb-inational pathway is absent.

Studies on cultured human cells have confirmed thefact that the repair defect in ataxia telangiectasia isrecessive, i.e., both copies of this particular gene must bedefective in order for this repair defect to be expressed. InUstilago maydis, on the other hand, a new type of geneticdefect in DNA repair has been investigated and it has beenshown that the cells become radiosensitive when they containone defective copy and one normal copy of this gene. Thissuggests that the defective gene product is incapable ofrepairing DNA damage itself and further that it interfereswith the normal gene product in the execution of its repairfunction. The defective gene product has not been identifiedbut it appears to play a key role in DNA replication, recomb-ination and repair.

A long-term experiment has been initiated to studythe effect of repair inhibitors on the induction of tumors inirradiated rats. Chemical studies on the constituentsreleased from the cell wall of M. radiodurans during irrad-iation are in progress. Methods are being developed to furtherstudy the distribution of polypryrimidine tracts in DNA.

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Experiments to define a new type of mutation in bacteriophageare nearing completion. These mutants may be useful forstudies on the mechanism of translation of the genetic codeby the bacterial ribosome.

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1.1 VERBAL PRESENTATIONS

1.1.1 Lectures or Seminars

Marko, A.M. - "Population and Occupational Exposuresand Limits", presented at Meeting of Ontario RoyalCommission on Electric Power Planning (PorterCommission), CRNL, 26 March 1976.

Marko, A.M. - "Defective DNA Repair in Cultured Human(ataxia telangiectasia) Fibroblasts", Paper byM.C. Paterson presented at the Nineteenth AnnualMeeting of the Canadian Federation of BiologicalSocieties, Dalhousie University, Halifax,15-18 June 1976.

Marko, A.M. - "Radiation and Health Physics", Lectureto Environmental Students, York and WaterlooUniversities, Sheridan Park, 25 November 1976.

1.1.2 Local Talks

Marko, A.M. - "Radiation Effects on Man", FellowesHigh School, Environmental Geography Class, Gr. 13,Pembroke, 15 January 1976.

Marko, A.M. - "Activities of the Biology and HealthPhysics Division", Presentation to Mr. Ross Campbell,Chairman of the Board, AECL, CRNL, 14 April 197 6.

Marko, A.M. - "Programs on Levels and Effects ofRadiation" Presentation to AECL Board of Directors,11 May 1976.

Marko, A.M. - "Effects of Radiation on Humans", SummerStudent Lecture, 11 June 1976.

Marko, A.M. - "Objectives of the Biology Branch",Presentation to A Mooradian, CRNL, 10 August 1976.

Marko, A.M. - Biology and Health Physics Colloquium,"Radiation Biology for the Non-Biologist", CRNLMain Library, 20 August 1976.

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HEALTH PHYSICS BRANCH

byG. Cowper

2.1 Staff2.2 Fast Neutron Dosimetry

2.2.1 Leakage Spectra from 2 3 8U Spheres ContainingSources of 14-MeV or Fission Neutrons

2.2.2 Neutron Spectrometry Using HydrogenousScintillators

2.2.3 Legendre Expansion Coefficients from TabulatedAngular Distributions in the ENDF/B Library

2.2.4 Compendium of Neutron Spectra for CriticalityAccident Dosimetry

2.2.5 Results for the Second Personnel DosimetryIntercomparison Study

2.2.6 Analytical Expressions for the ExcitationFunctions of Threshold Reactions

2.2.7 Spectra of Neutrons Transmitted and Multiply-scattered by Concrete Walls

2.2.3 Calculated Spectra and Attenuation of 14.7 MeVNeutrons Transmitted by Concrete

2.2.9 Measured Attenuation of 14.7 MeV Neutrons byOrdinary Concrete

2.2.10 Effects of Sub-Threshold Fission on NeutronDose Measurements with 237Np Detectors

2.2.11 Spectra and Dosimetry of Therapeutic Beams ofFast Neutrons in a Water Phantom

2.2.12 Neutron Spectral Measurements Using Propor-tional Counters

2.3 Thermoluminescence Dosimetry2.4 Safeguards Monitoring2.5 Radiation Detectors2.6 Radiation Monitoring Instruments

2.6.1 Wide Range 3Y Survey Meter AEP-52882.6.2 Portable Contamination Monitor AEP-52972.6.3 Alpha-in-Air Monitor AEP-101102.6.4 Low Level y Dose Rate Meter AEP-5301

2.7 Hazards from Tritium Produced in a 3He NeutronFlux Control Rig

2.8 Monitoring Noble Gas Fission Products in Air Effluents2.9 Tritium Monitoring

2.9.1 Tritium-in-Air Monitoring2.9.2 Tritium-in-Water Monitoring

2.10 Energy Loss in Thin Films2.11 Iodine Monitoring

2.11.1 Detection of 131I in Air2.11.2 Detection of 125I

2.12 Atmospheric Diffusion Data Analysis2.13 Microscopic Flying Spot Scanner

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2.14 Routine Dose Monitoring2.14.1 Body Radiation Doses2.14.2 Hand Radiation Doses

2.15 Publications2.16 Verbal Presentations

2.16.1 Local Talks

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2.1 STAFF

Branch Head

Secretary

G. Cowper

B. Lucas

W.G. CrossH. IngB.J. Tymons (1)

Assistants P.J. BungeD.J- RobertsonB.C. Greiner

A.R. Jones Assistants A.H. OhnoW.F. RichterP. Ruhe (2)

R.V. Osborne Assistants A.S. CoveartN.W. Tepley

R.M. Holford Assistant J.G. Plato

Personnel Monitoring R.M. Rondeau (Miss)J.M. Vincent (Mrs.)

Draftsmen B.A. MacDonald (3)J.H. Sneddon (3)

(1) Post-doctoral fellow(2) Student from the University of Waterloo working

with A.R. Jones reported 30 August 1976(3) On loan from the drawing office

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2.2 FAST NEUTRON DOSIMETRY

2.2.1 Leakage Spectra from 2 3 8U Spheres Containing Sourcesof 14-MeV or Fission Neutrons - H. Ing and W.G. Cross

Leakage spectra from 2 3 8U spheres (5 to 50 cmradius) containing sources of 14-MeV or fissionneutrons at the centre have been computed using the05R Monte Carlo code. These calculations were per-formed to assess the usefulness of U-shielded sourcesfor radiobiological irradiations and calibratingneutron dosimeters as well as for checking a simplemodel proposed earlier(-' for predicting shapes ofleakage spectra from enriched critical assemblies.

Our calculations show that for the 14-MeVsource, fission and inelastic neutron scatteringremoves neutrons from the 14-MeV peak to form abroad distribution (centered below 1 MeV) whichdegrades in average energy with increasing spheresize. For the 10-cm radius spheres, more than 90%of the neutrons are in the energy region below 5 MeV.This fraction, of course, increases with increasingsphere size. The total leakage fluence exceedsthat from the original source for spheres up toabout 30-cm radius, with maximum fluence for 12-cmspheres. For a T-D neutron generator with 10 X 1 n/soutput, the total neutron output from a 10-cm radiussphere is about 2.8 x 1011 n/s giving a dose rateof 200 rad/h (2 Gy/h) at a distance of 30 cm. Thus,in spite of the flux multiplication, the dose ratefrom the assembly is still slightly lower than thatfrom the unshielded source. The flux multiplicationhas been checked experimentally by surrounding a T-Dsource with fuel pellets of depleted U and measuringthe neutron output with a long counter.

In the case of a fission neutron source,competition between inelastic scattering and fissionin the 2 3 8U sphere causes the leakage spectrum tobroaden and to degrade in average energy with increas-ing sphere size. For radii of 10 and 30 cm, theaverage energies are 0.9 and 0.3 MeV respectively.

(1) W.G. Cross and H. Ing, 1973, in "NeutronMonitoring for Radiation Protection Purposes",Vol. 1 (IAEA, Vienna) p. 73

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There is negligible fluence below about 1 keVeven for radii as large as 50 cm. These spectraare in qualitative agreement with those predictedby the simple model in which the spectral shape wasdetermined by competition between fission andevaporation processes.

From the computed spectra, we also investigatedthe response of several activation and damage trackneutron dosimeters in order to determine which ismost suitable for measuring doses for irradiationsusing U-moderated assemblies. All dosimeters showedlarge variations with spectral changes. Of thosestudied, the 237Np damage track detector was leastsensitive to spectral changes produced by 2 3 8U.Such a detector calibrated with 14-MeV neutrons giveskerma readings accurate to better than ± 15% for 14-MeV neutrons moderated by up to 20 cm of 2 3 8U.

2.2.2 Neutron Spectrometry Using Hydrogenous Scintillators -H. Ing and W.G. Cross

Preliminary measurements of T-D neutrons with a5 cm x 5 cm NE-212 scintillator gave poor resolution(̂ 10%) in the unfolded peak and large oscillationsin the low energy region (< 3 MeV) of the neutronspectrum when the pulse-height distribution was un-folded with the FERDOR code using the response matrixsupplied with the code.

The poor resolution is attributed to the pooragreement between our actual detector response andthat in the response matrix as well as imperfectoptical coupling between the scintillator and thephotomultiplier. Our detector response is betterapproximated by the response matrix of Verbinskiet al(D and therefore the latter has been punchedon cards and interpolated to provide one which iscompatible with the "energy grouping" used in ourcode. To improve the intrinsic resolution, lightpipes of various shapes have been constructed andwill be tested to achieve optimum performance.

The oscillations in the low energy region areattributed to perturbations of the pulse-heightdistributions by gamma radiation. A standard n/ydiscrimination system using leading edge and zero

(1) Verbinski, V.V., Burrus, W.R., Love, T.A.,Zobel, W. and Hill, N.W., Nucl. Instr. Meth.68 (1968) p. 8

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cross-over timing has been assembled from Ortecmodules. Preliminary studies with radiation froma Pu-Be source indicate that this discriminatorwill eliminate gamma interference for neutronmeasurements above about 1 MeV.

2.2.3 Legendre Expansion Coefficients from TabulatedAngular Distributions in the ENDF/B Library ~=~H. Ing,W.G. Cross and B.C. Greiner

Treatment of angular distributions of scatteredneutrons in the 05R neutron transport code requiresdata in the form of Legendre expansion coefficients.Often, in the ENDF t lVB library, the angular distri-butions are tabulated as a function of the scatter-ing angle.

A program LEPFAD has been written to convertthe tabulated ENDF/D distributions to the Legendreexpansion representation and write the coefficientson a magnetic tape in BNDF/B format. The coeffi-cients are obtained by a least-squares fit to thstabulated distribution. The order of the Legendrepolynomial expansion can be specified by the useror LEPFAD will choose the lowest order that willproduce a fit satisfying a specified percentage errorat all tabulated points.

2.2.4 Compendium of Neutron Spectra for Crit.icalityAccident Dosimetry - H. Ing (In collaboration withS. Makra, Hungarian Academy of Sciences, CentralResearch Institute for Physics, Budapest, Hungary)

The preparation of the Compendium of NeutronSpectra for Criticality Accident Dosimetry, recomm-ended by the IAEA, has been completed. TheCompendium contains neutron spectra relevant tocriticality accidents and is for assisting thedetermination of neutron doses from readings ofneutron dosimeters such as activation or damagetrack detectors. Most of the spectra have beendrawn from calculations done at Chalk River NuclearLaboratories or the Hungarian Academy of Sciences.

The 292 spectra include spectra from:

(a) selected critical assemblies and solutions,

(1) Evaluated Nuclear Data File

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(b) fission neutrons, transmitted throughH 20, D 20, C, Be, Al, Fe, Cu, Pb,

2 3 S U ,polyethylene and concrete of variouscompositions and polyethylene,

(c) . H 20 and D20-moderated fission neutronstransmitted through Fe, Cu, Pb andconcrete,

(d) fission neutrons reflected from many ofthe above materials,

(e) 14-MeV neutrons transmitted by andreflected from some of these materials.

The spectra are given both in graphical and tabu-lated form.

Average cress sections for the followingreactions, x°3Rh(n,n')'°3mRh, J' 5In(n,n')*' 5 mIn,3 2S(n,p) 3 2P, 31P(n,p) 3 1Si, 2 3 7Np(n,f), 2 3 2Th(n,f)2 3 8U(n,f) are tabulated beside the spectral infor-mation. Average kerma, maximum dose, dose equivalentand gamma ray dose produced by neutrons interactingwith the body per unit incident neutron fluence arealso presented.

The Compendium, which contains 160 typed pages,has been sent to the IAEA for publication.

2.2.5 Results for the Second Personnel DosimetryIntercomparison Study - H. Ing and W.G. Cross

CRNL participated in the Second PersonnelDosimetry Intercomparison Study (PDIS) sponsored bythe Oak Ridge National Laboratory (ORNL). In thisintercomparison, four badges from CRNL were mailedto ORNL and exposed to four radiation fields producedby the HPRR reactor (unshielded, shielded with 10-cmFe and shielded with 12-cm lucite) and 14-MeV neu-trons. After irradiation, the badges were returnedto CRNL for analysis.

Because the exposures were small, most of theactivation dosimeters in the badges (intended forcritiuality accidents) were not suitable and, there-fore , the neutron and gamma dose equivalents wereobtained only from Th damage track detectors and6Li-shielded TLD chips respectively. The damagetrack detectors were read using the spark countingtechnique after etching along with detectors irra-diated with a known flu^nce of 14-MeV neutrons. Thecounts were converted to dose equivalents using theTh cross section and dose equivalent for 14-MeVneutrons and corresponding values for the unshieldedand shielded HPRR spectra.

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The TLD-700 dosimeters were calibrated withidentical chips (shielded with 6Li) exposed toknown doses from a 226Ra source. With the 6Lishield, the response of the y dosimeter to thermalneutrons was negligible. However, it was necessaryto correct the TLD-700 reading from the ganuT.a back-ground introduced by the adjacent Th radiators (ofthe neutron damage track detectors). Because themailing of badges to ORNL and back took much longerthan expected (seven weeks), the gamma dosimetershad a rather high background (up to 68% of the totalreading) which produced large uncertainties in thefinal gamma doses.

The table below shows the results obtained byCRNL and by ORNL. The agreement was surprisinglypoor. According to ORNL, the much higher gammadose-equivalents reported by all participants (12laboracories) might have resulted from inadvertentexposure of badges in a shipping storage area.

The CRNL badges were irradiated after the mainirradiations because of their late arrival, butsupposedly under identical conditions. If this istrue, we cannot explain the large differences in theneutron dose equivalent for the lucite-shielded andunshielded HPRR irradiations. ORNL did not quoteresults for the 14-MeV neutrons irradiation becausethe accelerator failed to operate properly.

Irradiation Source

Neutron DoseEquivalent

(mrem)CRNL ORNL

Gamma DoseEquivalent

(mrem)CRNL ORNL

Lucite-shieldedHPRR

HPRR

Steel-shieldedHPRR

14-MeV Neutrons

260 ± 50 383

210 + 33 404

510 + 90 523

5 ± 2

164 ± 22 41

72 ± 22

54 ± 22

76 + 22

16

8

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2.2.6 Analytical Expressions for the Excitation Functionsof Threshold Reactions - W.G. Cross and H. Ing

Analytical expressions for the energy-variationof the cross section for several threshold reactionsuseful in neutron dosimetry have been given pre-viously (D. Similar expression have now been obtain-ed for cross sections of the reactions 3 1P(n,p),2 7Al(n,a), 2*Mg(n,p) and 5 6Fe(n,p), .by fitting thedata from the 1974 CCDN compilation^' and its updateof May 1975. We have also fitted the energy varia-tion of kerma, charged particle surface dose, doseequivalent and surface dose from the ]H(n,y) reaction,all per unit fluence. These expressions have beenused to derive average cross sections for spectra offission and other neutrons transmitted throughshielding.

2.2.7 Spectra of Neutrons Transmitted and Multiply-scatteredby Concrete Walls - W.G. Cross and H. Ing

Spectra of neutrons from reactors and accelerators,transmitted through concrete shielding and multiply-reflected within a room, can have a high proportionof neutrons below 100 keV. In these circumstancesaccurate dose measurements require knowledge of theneutron spectrum because threshold detectors do notrespond to low energy neutrons whereas moderator-typedetectors (e.g., albedo dosimeters) are overly sensi-tive to low energy neutrons.

Using the 05R Monte Carlo program, we havecalculated spectra of neutrons transmitted by orreflected from concrete walls in various geometricalarrangements, in order to explore the extent of spec-tral variations. Sources include monoenergeticneutrons of 2.8 and 14.7 MeV, unmoderated fissionneutrons and spectra from light- and heavy-waterreactors. Spectra were calculated at various depths(to 1 m) in a wall for normally and isotropicallyincident neutrons. Effects of multiple reflectionsfrom walls of shielded rooms and long corridors wereinvestigated with the objective of finding conditionsproducing the "softest" spectra. No spectrum wasobtained with nearly as high a proportion of doseequivalent below 100 keV as has sometimes been derived

(1) W.G. Cross and H. Ing, Nucl. Sci. Eng. 5J3_,377 (1975)

(2) "Compilation of Threshold Reaction NeutronCross Sections for Neutron Dosimetry and OtherApplications", NEANDC-95U, Centre ENEA deCompilation de Donnees Neutroniques, Saclay,1974.

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from measurements with a rem-meter and recoil-proton counter.

For all these calculated spectra we evaluatedaverage cross sections for several thresholddetectors useful in dosimetry.

2.2.8 Calculated Spectra and Attenuation of 14.7 MeVNeutrons Transmitted by Concrete - W.G. Cross andH. Ing

The 05R Monte Carlo program has been used tocalculate spectra of neutrons transmitted throughvarious thicknesses of concrete up to 100 cm.Compared to similar but less extensive calculationsmade in 1973 (PR-B-97) inelastic scattering has nowbeen treated in much greater detail. Cross sectionsand elastic angular distributions were taken fromthe ENDF/B-IV library.

For incident 14.7 MeV neutrons, spectra ofemergent neutrons were calculated for

(a) a broad beam incident normally on slabs ofvarious thicknesses,

(b) an isotropic source against the same slabs,(c) a source at the centre of concrete spheres

of various sizes,(d) a source at the centre of a concrete shell,

4 m in diameter and 30 cm thick.

Spectra were also calculated at various depths in a100-cm thick block with normally or isotropicallyincident neutrons. For isotropic incidence attenua-tion is exponential at thicknesses > 10 cm but has ahigher slope at small thicknesses. For normal inci-dence the slope is initially smaller but beyond 40 cmbecomes the same as that for isotropic incidence.These characteristics can be understood in terms ofthe neutron angular distributions, which were recordedat each depth for three energy groups - 0 to 1, 1 to10 and 10 to 14.7 MeV. The angular distributionsof emergent neutrons have been used to explain someof the discordant results in measurements of attenua-tion lengths by different experimenters, usingdifferent geometrical arrangements.

Calculated attenuation length for slab geometrywas in agreement with that calculated by Roussin and

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Schmidt . For spherical geometry, the attenuationlength is nearly 20% higher than for slabs. Averagevalues of kerma and dose equivalent per unit neu-tron fluence and of cross sections for a number ofthreshold reactions useful in dosimetry were calcu-lated for all spectra. Effects of variations inconcrete componsition on spectra and attenuationhave been studied. As expected, attenuation is verydependent upon hydrogen content. Varying the propor-tions of Si, Ca and Al had an almost negligibleeffect on the attenuation length but replacing oxygenby these elements reduced it.

2.2.9 Measured Attenuation of 14.7 MeV Neutrons by OrdinaryConcrete - W.G. Cross and H. Ing

The results of existing measurements of theattenuation of 14 MeV neutrons in concrete are inpoor agreement^). At thicknesses exceeding about30 cm, attenuation is roughly exponential, withquoted values of the attenuation length varying from14.5 to 2 2 cm. In contrast, the length derived fromnuclear cross sections by Monte Carlo calculationsis 11.5 to 13.5 cm.

We have measured dose attenuation at depths to100 cm in a large (2 x 2.4 x 1.4 m) assembly of con-crete blocks. The 14.7 MeV neutron source was 1.4 mfrom the assembly. Two measurements of attenuationwere made, the first with a Hurst-type proportionalcounter dosemeter (FN2/3) placed successively atdifferent positions in the block and the second with2 3 7Np damage track detectors located at 10 cm inter-vals in depth and irradiated simultaneously. Sincethe ratio of dose to detector reading varies withthe neutron spectrum, spectra calculated at eachdetector location were used to make small correctionsto dose measurements.

Differences from previous measurements are:

(a) the lateral dimensions of the block areeffectively "infinite",

(b) neutrons are incident in a broad beamroughly normal to the surface, thus re-producing the geometry of the calculations,

(1) R.W. Roussin and F.A.R. Schmidt, Nucl. Eng.Design, 15_, 319 (1971)

(2) D. Bozyap and L.R. Day, Health Physics 2j[,101 (1975)

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(c) the detector is always well shieldedfrom room-scattered neutrons.

Values obtained for the attenuation length are13 ± 1 cm and 13.7 ± 1 cm (p = 2300 kg/m3) for thetwo experiments, in agreement with theory.

We have also measured the depth distributionof thermal fluence, using bare and cadmium shieldedgold foils. The elemental composition of the con-crete is being determined, primarily by activationanalysis.

2.2.10 Effects of Sub-Threshold Fission on Neutron DoseMeasurements with 23 7Np Detectors - W.G. Cross andH. Ing

237Np provides a particularly useful fissiondamage-track radiator for fast neutron dose measure-ments. Although the fission cross section exhibitsa "threshold" around 200 keV, it is appreciable atlower energies and this sub-threshold fission canaffect dose measurements. While values of crosssections between 1 eV and 100 keV have been avail-able since 1972, their effect on dose determinationshad not been calculated.

To compute the effect of sub-threshold fissionon neutron spectra distributed over a wide energyregion, 3 000 point-by-point cross-section valueswere fitted by an analytical function of energy.The response of a 2 3 7Np detector was then calculatedfor typical spectra from light and heavy waterreactors, before and after the neutrons pass throughFe and concrete shields. For most of these spectra,sub-threshold fission affects the response by lessthan 10%. The contribution is larger for neutronstransmitted through heavy elements (Fe, Cu, U) ormultiply scattered from light elements. In thesecircumstances, approximate knowledge of the spectrumpermits corrections for sub-threshold fission to bemade to Np dosimeter readings.

2.2.11 Spectra and Dosimetry of Therapeutic Beams of FastNeutrons in a Water Phantom - W.G. Cross and H. Ing

Spectra at various depths and lateral positionsinside a water phantom, irradiated by neutrons fromthe 9Be(d,n) reaction, have been calculated previous-ly (PR-B-108). These calculations have been repeatedusing an incident spectrum slightly different fromthat measured for the Hammersmith Hospital cyclotron.

- 19 -

This spectrum contains a higher proportion ofneutrons below 1 MeV and is believed to be a betterapproximation to that of the actual therapy beam.

For both incident spectra, the spectra in thephantom along the beam axis show remarkably littlechange with depth, except in the first 5 cm fromthe surface. Over this region, the proportion oflow energy neutrons can either increase or decreasedepending on the shape of the incident spectrum.Tha changes with depth are too small to account forRBE variations of more than a few percent and alsoappear inconsistent with insignificant changes in OER re-ported earlier(D. At depths exceeding 5 cm, bothcalculated depth dose distributions agree well withthat measured at Hammersmith; but close to thesurface, better agreement is obtained for the inci-dent spectrum containing a higher portion of low-energy neutrons. These neutrons have no significanteffect on the build-up of dose at the surface.

The computer programs for this calculation havebeen improved to permit application to beams up to20 x 20 cm and to reduce statistical fluctuations inthe spectra obtained.

2.2.12 Neutron Spectral Measurements Using ProportionalCounters - B.J. Tymons and H. Ing

Work has now been completed on the energycalibration procedures for four different sphericalproportional counters. The large 7.63 cm radiusSP6 counter will be calibrated simply using mono-energetic neutrons from the D(D, 3He)n reaction.The 2 cm radius SP2 counter will be calibrated usingresonances in absorber materials placed around thedetectors and inside a graphite assembly containinga Pu-Be source. For the 10-atmosphere hydrogen-filled SP2 counter, SiO2 is the absorber and theoxygen resonances at 0.43 and 1.0 MeV are used.For the 4-atmosphere counter, only the 0.43 MeVresonance is used. Aluminum oxide was tried as theabsorber but gave inferior resolution because ofinterference from aluminum resonances. The oneatmosphere counter uses fluorine (in teflon) as theresonance absorber. The 50 keV and 100 keV reson-ances are used as the calibration points. The aboveprocedures have been tested with suitable monoener-getic neutrons provided by the Van de Graaff

(1) R.J. Berry and D.K. Bewley, Brit. J. Radiol.49, 458 (1C76)

- 20 -

accelerator at the National Research Council inOttawa.

2.3 THERMOLUMINESCENCE DOSIMETRY - A.R. Jones

Seven Automatic TLD Readers have been receivedfrom Canadian Admiral Ltd. and one from AptecEngineering Ltd. Of these, six have been tested,corrected and then modified to suit the differentrequirements of Ontario Hydro and Health & WelfareCanada each of which have received three readers.The remaining two readers destined for OntarioHydro and Hydro-Quebec are nearly completed. Main-tenance technicians and operators from the threeagencies have been trained. Drawings of the threedifferent sets of modifications have been made aswell as up-dating of the original drawings asrequired during the construction. Work on a main-tenance and operational manual for the new readercontinues.

The majority of CRNL employees (those withbadge numbers below 2,000) have been equipped withthe new TLD holders. Poorly bonded clips have causedthe most numerous complaints during service. Defec-tive holders are being replaced by the manufacturerand it would appear advisable in future to modifythe design so that the holding clip is held with ametal rather than a plastic rivet.

The introduction of the new holder is reducingthe incidence of spurious readings. For example,67 spurious readings were detected in 1 600 dosimeterplaques worn in the old film badges. For those fromthe new holders the incidence had dropped to threespurious readings in 1,000 plaques. A further indi-cation that dirt is being effectively excluded bythe new holder is obtained by a comparison betweenthe penetrating and skin doses received by workerswho normally are very lightly exposed (< 20 mrempenetrating dose and < 60 mrem skin dose).

Average and Standard Deviations in mrem

New Holders Film Badges

Penetrating Dose

Skin Dose

3.7 ± 2.7

4.0 ± 6.4

4.2 ± 3.4

21.2 ± 15.3

- 21 -

With the new holder the readings for the akinpenetrating dose accord well but the skin dosereading is considerably higher in the case of TLDsheld in the film badges where the thin TLD isparticularly exposed to dirt.

Preparations have been completed to changeover in January 1977 from unmounted TLD chips toindividually calibrated plaque-mounted TLDs forenvironmental gamma dosimetry. The purpose is toimprove the reliability and precision of low levelmeasurements and to reduce the time spent in measure-ment- 350 pairs of TLDs (thick and thin) were sen-sitized by exposure to 60Co y~rays and then annealedat 300°C for 45 minutes while exposed to UV. Theywere then individually calibrated and are packagedtwo to a TLD holder. Tests have been made of 30 ofthese packages in an outdoor measurement of a smallexposure of 18 mR where a standard deviation of lessthan 8% was observed. The increase in backgrounddue to holding them between the aluminum slabs wasnot detectable and was certainly less than 1 mR/month.

Fading tests were made on the sensitized TLDplaques by exposing batches to equal exposures atdifferent times over a period of 5,000 hours. Theywere stored at temperatures ranging between 22 and27°C and the estimated annual fading rate was 6%.Jnsensitized TLDs, which had been preannealed at 80°for 16 hours, were found to have a fading rate of5%/year. Both fading rates are acceptably low forannual environmental measurements. An oven with aUV window is being constructed to anneal up to 100sensitized TLDs at a time.

Tests have begun on the performance ofunsensitized TLDs when exposed at low rates over athree month period, using both annealed and unannealedTLDs, for comparison of their fading. If the resultsof these tests prove satisfactory it would be tech-nically feasible to monitor the great majority ofCRNL workers (who receive less than 0.5 rem/year) ona quarterly basis with greater precision and sensi-tivity and a reduction in work.

2.4 SAFEGUARDS MONITORING - A.R. Jones

A new collimated array of detectors has beenbuilt for use at Douglas Point. The array containseleven detectors in line to be aligned with eleven

- 22 -

touching fuel bundles- The electronic circuits arethe same as those used for the Pickering fuel bundlemonitor. The problem of reliably de- ?r>ting a dummybundle (i.e., an object which looks like a fuelbundle and may be one with little or no irradiation)is more difficult at Douglas Point because thebundles are closer and there may be some uncertaintyabout the spacing.

The array was tested with a full array of fuelcontaining one dummy bundle (i.e., a fuel bundle oflow irradiation and long decay time). The averagesignal from the two nearest neighbours was 3.2 timesgreater than the sianal from the dummy. Next, every"•ther fuel buno.le was removed and a comparison was madebetween the signals from the occupied and emptysites in the arrav. The average of signals obtainedfrom bundles was 2.1 times greater than those obtain-ed irom vacant sites. The dummy bundle is easier todetec : than a vacant site probably because the dummybundle shields the detector opposite from neighbour-ing bundles.

Calculations indicated that there is an optimumcollimator cone angle to minimize dependence onprecvse alignment of bundle and detector. Threein.°sin;E were made to lessen the cone angle to thisvalue and the detectors were tested with the array ofbundles from which every other one was removed. Withthis narrower cone the discrimination factor was3.4 : 1.

All eleven collimator cones are being narrowedbefore the collimator is shipped to Douglas Pointfor further testing.

2.5 RADIATION DETECTORS - A.R. Jones

For gamma dosimetry at low exposure rates(below 2 rnR/hour) a GM counter must have high sensi-tivity for good statistical precision and speed ofresponse. The energy response of a high sensitivityGM counter (Philips type 18545) has been measuredand an appropriate correction filter is being designedto permit its use down to 50 keV. Its high sensiti-vity, particularly at low energies, makes such measure-ments difficult and it first had to be calibrated inits current mode in the logarithmic range.

To extend its usefulness to higher doses acounting loss correction circuit has been designed.

- 23 -

At the lower end of the range the response of allcounters are non-linear in their response to y-raysbecause of internal radioactivity and their sensi-tivity to cosmic rays. Circuits are being designedto correct for this zero signal.

2.6 RADIATION MONITORING INSTRUMENTS - A.R. Jones

2.6.1 Wide Range 3y Survey Meter AEP-5288

The mechanical redesign has been completed anda new engineering prototype, which is smaller andlighter than the first, has been built. It is nowbeing tested. Aptec Engineering Ltd. have suppliedsample GM counters to replace the type originallyselected which are no longer available. Thesecounters have been tested and found satisfactory asreplacements although a new energy dependence filterhas had to be designed.

2.6.2 Portable Contamination Monitor AEP-5297

The engineering prototype has been built andtested in the laboratory by the R. & I.S. Branch.Changes are being made to the design to meet theusers' requirements. Most important of these changesis the abandonment of a circuit which automaticallyadjusted the time constant to keep the statisticalprecision constant at all count rates. Instead achoice of two fixed time constants will be providedwhich permits faster response to weak sources at theexpense of accuracy.

2.6.3 Alpha-in-Air Monitor AEP-10110

The design of the head amplifier has beenmodified to reduce its sensitivity to RF interferencefrom an arc welder.

2.6.4 Low Level y Dose Rate Meter AEP-5301

The design of a low range dose rate meter for doserates from background up to 2 mrad/h (20 pGy/h) has begun.The dose rate meter will permit radiation surveys tobe made with adequate speed and precision at levelstoo low for the Wide Range Sy Survey Meter AEP-5288.

The dose rate meter uses a high sensitivity GMcounter (Philips 18545) and will display the doserates with a single numerical display. To conservebattery life the meter will be automatically switchedoff when it is set down.

- 24 -

2.7 HAZARDS FROM TRITIUM PRODUCED IN A 3He NEUTRON FLUXCONTROL RIG - R.V. Osborne

In one of the loops in the NRX reactor, 3Hecontrols the neutron flux reaching experimental fuel.Tritium is formed by the (n,p) reaction on the 3Heat rates up to 1.4 mCi/s (̂ 50 MBq/s). Health physicswork associated with the rig has been to:

- analyze the ways in which operators could beexposed to tritium during normal operationand following procedural or equipmentfailures,

- estimate dose commitments that could resultfrom such exposures,

- evaluate the protective devices and procedures,and

- design and build the instruments required fcrradiation protection.

The control rig works by varying the pressureof 3He in tubing around the fuel elements in thereactor core; control being with out-of-core compon-ents in a ventilated glove box. The tritium iscatalytically oxidized and collected on molecularsieve contained in the closed rig.

Exposure of operators to tritium beta radiationcan only occur if the tritium escapes from the 3Hecontainment. The analysis considered "worst case"acute and chronic releases combined with varioussystem and procedural faults. These included lossof ventilation, loss of glove box integrity, failureto collect oxidized tritium and failure to oxidize.Tritium inhalation and permeation through unprotectedand protected skin from contaminated components orfrom contaminated air were considered in the analysis.

Conservative upper limits have been estimatedfor operating times from 1 day to 1 year.

The estimated doses ranged from less than afew mrem for acute releases when everything else isoperating normally to a dose of hundreds of rem thatwould result from inhalation of glove box air contam-inated with tritium released as oxide after accumu-lating for several days without collection on mole-cular sieve. This possibility required four indepen-dent system or procedural faults, including disregardof elementary radiation protection practices. Thecompleted analysis indicated that the greater thedose commitment, then the greater the number of faultsthat would have to occur.

- 25 -

The analysis emphasized the importance ofensuring that any oxide formed is collected onmolecular sieve after each operating day and that,because of an exponential increase in collectioninefficiency for oxide with time, the water loadingof the sieve is limited to 5%.

To meet the instrumental requirements forradiation protection, three monitors have beendesigned and built to provide warning of and estimate:

- release of tritium to the glove box and thenceto the exhaust,

- release of tritium from the glove box toambient air, and

- uncollected tritium oxide in the closed rig.

The exhaust monitor (AEP-5293), described in detailin PR-B-108, monitors and records the concentrationof tritium in the glove box exhaust air, from ^ 1 0 0pCi/m3 to ^ 10 kCi/m3 (4 MBq/m3 to 400 TBg/m3) and inte-grates and digitally displays cumulative tritiumlosses. The ambient air monitor has been adaptedfrom the portable unit AEP-5215A by adding a line-operated power supply, a line-operated pump and aconcentration level alarm. The response times ofboth these monitors are less than 10 s and the alarmsmay be set at or above a concentration that corres-ponds to a dose commitment rate of less than 1 mrem/min for unprotected exposures to chronic releases.The in-line monitors (AEP-5299) are two small (2.5cm3) ionization chambers, each with a DC amplifierand chart recorder. The three-decade dynamic rangeshave been selected to encompass the range of concen-trations of tritium upstream of the oxidizer andmolecular sieve and the (lower) range of concentra-tions downstream of the sieve. All three designs ofthe monitor have been completed and are beingcommissioned on the rig.

2.8 MONITORING NOBLE GAS FISSION PRODUCTS IN AIREFFLUENTS - R.V. Osborne

Monitors on the gaseous effluents from a 9 9Moextraction facility and a fuel test facility arerequired for two reasons; to warn of an abnormalityor change in operation, particularly with respectto release of the longer-lived xenons and to providesufficient identification of any released gas toallow estimation of doses to any locally exposedgroup. For the former a simple device is sufficient

- 26 -

and desirable. For the latter a spectroscopicsystem is needed.. This is because a simple estimateof the product Ci-MeV(y) for the released gas - forwhich suitably filtered GM or scintillator detectorsmay be used - is not appropriate for releases fromfacilities that may have the shorter-lived kryptonsand xenons present and where semi-infinite cloudapproximations are invalid.

A sampling ionization chamber is sufficientlyaccurate and sensitive for the former requirements;the calculated response per becquerel of radioactivenoble gases released varies within a factor of two.Various irradiation and target decay times have beenconsidered in the calculation for the 9 °Mo extractionfacility; two fuel defect models and two releasepathways - directly to a swept airspace and via thereactor loop coolant - have been considered for thefuel test facility. The design of the air monitorAEP-5293, designed for monitoring tritium releasedfrom other equipment (see section 2.7) has thereforebeen broadened so that it may be used on both of theseeffluents to warn of unusual releases and to providean approximate but continuous measure of the totalactivity released.

Engineering drawings for the monitor have beencompleted and two units are being built. The manualhas been partly completed.

2.9 TRITIUM MONITORING - R.V. Osborne

2.9.1 Tritium-in-Air Monitoring

During the year the engineering of threeinstruments h^s been completed in addition to thosenoted in sections 2.7 and 2.8. These are theinstalled monitor AEP-5275, the portable monitorAEP-5215A and the tritium calibrator AEP-5284.

The completed prototype of AEP-5275 has beentested in the laboratory and is currently at PickeringGenerating Station for field tests and evaluation.Two of the monitors installed at Bruce GeneratingStation nave been inspected and operating staffguided in commissioning them.

The main change to the portable monitor (AEP-5215A) has been to decrease the transient signal thatwas observed when switching to the most sensitiverange; this has been accomplished by rearrangementof the high impedence (> 1 Pfl) switching wafers.

- 27 -

Development of the transportable monitorAEP-5270 (see PR-B-108) has been given second priorityduring the year and the laboratory prototype has onlybeen partly tested. However the designs of severalof the component units have been used for the efflu-ent monitor AEP-5293 described in section 2.7; forexample, the electrometer package (AEP-5300) and thedisplay circuit.

Manuals for two of the instruments have beencompleted; two others are being prepared.

2.9.2 Tritium-in-Water Monitoring

The major problem in water monitoring remainsthe preparation of the water sample. Effectivefilters will operate for only a few days at somepower stations so that continuous monitoring isexpensive in man-hours.MThe radiant still {see AECL-4932, J.G. Bayly et al) U J offers potential savingin man-hours and greater effectiveness in supplyinga clean water sample to the water monitor AEP-5252.A 1 kW prototype has been tested in the laboratoryand the flow of water that can be obtained is suffi-cient to give a response time with the water monitorof less than 10 minutes. The change in the isotopicratio 3H/1H between sampled water and distillate isless than 1% and is inconsequential for this applica-tion. The results are sufficiently encouraging forthis approach to be pursued.

2.10 ENERGY LOSS IN THIN FILMS - K. Chang and R.V. Osborne

During the summer the vacuum system and analyzerwere completely reassembled in a different labora-tory. Because loss peaks were not detected witheither formvar or carbon films, the acceptance angleof the analyzer was increased by moving the filmholder closer to the defining aperture of the analy-zer. Additionally, carbon films thinner (2 to 4 m)and more robust than previously used were obtainedfrom J. Gallant (Nuclear Physics Branch).

With the adjusted angle of acceptance, thebroad 25 eV single loss peak has been observed ata beam energy of 1.7 keV. Stability of the beamcontinued to be a problem and prevented any quanti-tative estimations. To improve this, the gun f La-ment and electrode supplies have been modified bitthe performance has not yet been determined.

(1) J.G. Bayly, D. Gresham and J. Kolk, "The RadiantStill", Atomic Energy of Canada Limited ReportAECL-4932 (1975).

- 28 -

2.11 IODINE MONITORING - R.M. Holford

2.11.1 Detection of 1 3 1I in Air

The prototype Iodine in air monitor AEP-5217has been in operation in the NRX reactor buildingfor most of the year. The steel-wool filter, usedto protect the pump from the biomine which is addedto the air stream in trace quantities to improvethe efficiency of tho charcoal-loaded filter paper,has been replaced by a commercial filter containinga replaceable charcoal cartridge. This unit has amuch lower resistance to air flow, and will probablyrequire much less frequent replacement of the car-tridge. Unlike the steel-wool its condition cannotbe determined by visual inspection, and so to deter-mine the useful lifetime of the cartridge a checkfor bromine in the air leaving the filter is beingmade every few days.

It was discovered that, due to leaks in the air-line and other causes, the flowmeter in series withthe air pump was considerably over-estimating therate at which air was being drawn from the samplingduct. The air-line has been modified to reduce thenumber of joints required, and the flowmeter hasbeen moved to the inlet side of the air-line. Onlythe particulate filter precedes it; this is thoughtadvisable so as to reduce possible contamination pro-blems. A glass flowmeter has been specified toreduce absorption of radio-iodine from the airstream.

Checks have been made on the collection efficiencyof the filter medium by backing it up with a "Maypack" (a charcoal cartridge). These showed that withthe standard filter medium. Whatman type ACG/B char-coal-loaded filter paper, penetration was significantwhen sampling for a full 24 hours at the maximumdesign rate of 20 litres/min. Penetration was insigni-ficant if the flow rate was reduced to 10 litres/minor the sampling period to 8 hours. The problem isapparently solved by the use of an alternative paper,Dexter X-1230. Use of this paper was not recommendedpreviously because of high side leakage in the filterhead, but now that the flowmeter is on the inlet sideleakage can be allowed for as long as it is stableand repeatable. With the Dexter paper side leakageis between 10 and 20% of flow, but the flow rate atthe input is stable to within 5%.

- 29 -

Frequent checks are also made on the stabilityof the scintillator, photomultiplier tube and elec-tronics used for radiation detection, using a barium-133 source. Stability has generally been good,although on two occasions during the year there weresudden drifts with no obvious cause. Experimentshave also been carried out to determine the sourceof the background count rate. In the present situa-tion, as a stack monitor in the NRX building, themost important source of "background" is apparentlythe other isotopes of iodine. Some of these, parti-cularly 1-134 and 1-136, have half-lives which arecomparable with the response time of the instrument.They therefore rapidly reach an equilibrium level ofactivity on the filter paper and are indistinguish-able from background caused by noble gasses or byexternal radiation.

The three other longer-lived isotopes of iodineproduced by the reactor, 1-132, -133 and -135, alsoappear to have small but positive effects on the netcount rate. The effect of 1-133 is rather criticallydependent on correct adjustment of the instrumenthowever, since its main y-ray peak is only just abovethe background subtract "window" and if the gaindrifts downwards the peak may enter the background"window" and produce a negative reading on the instru-ment. This was observed during one of the periods ofgain drift described above.

2.11.2 Detection of 1 2 5I

A prototype of the 125I monitor, AEP-5285, hasbeen constructed and tested. With a good qualitythin sodium iodide scintillation detector it givesresults very close to those calculated from analysisof a gamma ray spectrum on a multi-channel analyzerusing the same detector. The main limitations onits accuracy appear to be background and countingstatistics at the low activity end of its range(̂ 3 nCi [100 BqJ); the augmentation of the real coin-cidence counting rate by random coincidences due tothe response time of the detector (̂ 0.25 us) at thehigh activity end of its range (̂ 30 yCi [1 MBq]), andthe distributional error in an extended source at allactivities.

2.12 ATMOSPHERIC DIFFUSION DATA ANALYSIS - R.M. Holford

Work on this project has been limited to acontinuation of processing of all new data into the

- 30 -

compact form to provide a back-up and to facilitatefurther analysis, and to the running of a trial pro-gram to produce probability distributions of thediffusion coefficients for each of the five samplingstations and for end of the past six years. Ingeneral the exponential distribution already reportedfor the earlier data (pre-1970) was confirmed, butthe graphs tend to be concave upwards on a log scale,i.e., there are more very low and very high valuesthan predicted. Some of the low values may be causedby instrumental instability rather than genuine

Ar, but in view of the number of samples involvedthis is unlikely to explain all of the observedexcess. Another possible explanation is that theywere caused by the gamma field of the plume at timeswhen it was close to, Lut not actually touching thedetector. Likewise some of the high values mayrepresent instrument malfunctions which editing ofthe data has failed to remove. Whether this is socould possibly be determined by a detailed analysisof all periods of high "tlAr readings, but it wouldbe a time-consuming operation involving a lot of sub-jective judgements. If the meteorological experimentis to be continued in any form an overhaul of theinstrumentation to improve reliability is thereforerecommended.

2.13 MICROSCOPIC FLYING SPOT SCANNER - R.M. Holford

Thir unit is being converted for use in countingetch-pits in Kodak LR115 cellulose nitrate foils,used for detection of heavy ionizing particles. Aslow mode cf scanning will be used to improve thesignal to noise ratio, and to facilitate this a newamplifier has been designed which is capable ofdriving either the vertical or the horizontal windingsof the deflection yoke. Inexpensive power transistorsare used and acceptably fast response is achieve withfewer stability problems than in previous designs.

Horizontal scanning in both directions, using anup-down counter and a digital-to-analog converter,was investigated to the point of prototype construc-tion but had to be rejected because reliable spot-counting requires that the result of the currentline-scan be compared with the previous one, (displacedby one vertical unit). Pulses occurring at the samepoint in both scans are presumed to represent partsof the same object and are only counted once. In up-down mode there is a displacement between the "up"and "down" scans due to the time lags in the various

2.14

2.14.1

- 31 -

parts of the circuit, and this displacement wasfound to be too large to be easily corrected forin any simple way. Instead of this a unidirectionalscan will be used with a fairly slow retrace soas to avoid overloading the deflection amplifiers.The digital to analog converter also failed to workwell for the horizontal scan, although it is satis-factory for the slow vertical scan, and has beenreplaced by a circuit based on an operational ampli-fier integrator. Using this mode of scanning, anda variable persistence oscilloscope as a displaydevice, an acceptable image of an etched LR115 foilcan now be produced.

ROUTINE DOSE MONITORING - R.M. Rondeau & J.M. Vincent

Body Radiation Doses

In the fourteen week period ending 19 Novemberand the calendar year to this date there are thefollowing distributions of radiation exposures.

Pentratinv Radiation Dose - CRNL

Dose Rangerems

No radiation0 - 0.490.50 - 0.991.00 - 1.491.50 - 1.992.00 - 2.492.50 - 2.993.00 - 3.493.50 - 3.994.00 - 4.49

Average doseper monitoredperson

Average doseper exposedperson

Fourteen

No. ofmonitoredpersons

1052439

78201

Weeks

TotalDose

Man-rem

0165.6851.9223.291.62

92 mrem

96 mrem

Calendar Year

No. ofmonitoredpersons

482174154133613519955

TotalDose

Man-rem

0275.43114.60162.85107.5177.0350.9629.7318.1920.74

324 mrem

330 mrem

- 32 -

Penetrating Radiation Dose -

Dose Rangerems

No radiation0 - 0.490.50 - 0.991.00 - 1.491.50 - 1.992.00 - 2.492.50 - 2.993.00 - 3.493.50 - 3.99

Average doseper monitoredperson

Average doseper exposedperson

Fourteen Weeks

No. ofmonitoredpersons

38206

71

TotalDose

. Man-reifi

012.834.521.01

7 3 mrem

86 mrem

CP

Calendar Year

No. ofmonitoredpersons

2419914724011

253

280

TotalDose

Man-rem

025.5710.708.383.408.9503.023.85

mrem

mrem

Penetrating Radiation Dose -

uose Kancjerems

No radiation0 - 0.490.50 - 0.991.00 - 1.491.59 - 1.992.00 - 2.49

Average doseper monitoredperson

Average doseper exposedperson

Fourteen Weeks

No. ofmonitoredpersons

1513251

TotalDose

Man-rem

04.163.371.06

4 5 mrem

226 mrem

PP

Calendar Year

No. ofmonitoredpersons

1244113641

TotalDose

Man-rem

04.959.217.016.822.03

159 mrem

462 mrem

- 33 -

Surface Radiation Dose - CRNL

Dose Rangereins

No radiation0 - 0.490.50 - 0.991.00 - 1.491.50 - 1.992.00 - 2.492.50 - 2.993.00 - 2.493.50 - 3.994.00 - 4.494.50 - 4.995.50 - 5.996.00 - 6.49

Average doseper monitoredperson

Average doseper exposedperson

Fourteen Weeks

No. ofmonitoredpersons

1052353132361241

124 :

TotalDose

Man-rem

0159.1993.2642.2720.499.212.69

nrem

129 mrem

Calendar Year

No. ofmonitoredpersons

48208814311791603620157756

TotalDose

Man-rem

0279.06101.35143.96156.52133.7798.4764.7756.6729.9233.3328.4637.46

440 mrem

448 mrem

Surface Radiation Dose - CP

Dose Rangerems

No radiation0 - 0.49U.50 - 0.991.00 - 1.491.50 - 1.992.00 - 2.492.50 - 2.993.00 - 3.494.00 - 4.494.50 - 4.995.00 - 5.49

Average doseper monitoredperson

Average doseper exposedperson

Fourteen Weeks

No. ofmonitoredpersons

37 ,200

933

TotalDose

Man-rem

016.486.373.375.20

125 mrem

146 mrem

Calendar Year

No. ofmonitoredpersons

241723095322221

432

478

TotalDose

Man-rem

020.4420.4411.378.696.105.096.088.499.915.11

mrem

mrem

- 34 -

Surface Radiation Dcse - PP

Dose Rangerems

No radiat ion0 - 0.490.50 - 0.991.00 - 1.491.50 - 1.992.00 - 2.49

Average doseper monitoredperson

Average doseper exposedperson

i

Fourteen Weeks

No ofmonitored

persons151

3251

46 i

227

Tota lDose

Man-rent04.163.431.06

nrem

mrem

Calendar Year

No. ofmonitored

persons124

3910

772

193

562

Tota lDose

Man-rem04.327.578.12

12.254.30

mrem

tnrem

The two-weekly administrative control limitsfor whole body doses were exceeded on one occasionat CRNL and on four occasions at Power Projects.

2.14.2 Hand Radiation Doses

In the calendar year and the 14 week periodending 3 December 1976 there were the followingdistributions of extremity doses as measured byfinger tip TLD's.

Dose Rangerems

less1.002.004.006.00

than 0.99- 1 . 9 9- 3.99- 5.99- 7.99

CRNLCalendar Fourteen

Year Weeks

1812619

20

655200

CalendarYear

361710

22

CPFourteen

Weeks

259000

CalendarYear

50000

PPFourteen

Weeks

20000

- 35 -

2.15 PUBLICATIONS

R.V. Osborne and A. Prini - Calibrator for Tritiumin Air.Monitors. May 1976. AECL-5378.

R.V. Osborne and A.S. Coveart - Manual for PortableTritium in Air Monitor AEP-5215 and AEP-5215A.Atomic Energy of Canada Limited UnpublishedInternal Report, CRNL-1199. May 1976.

A.R. Jones - Manual for the Use and Repair of AlphaAir Monitors AEP-5234 and AEP-10110. AtomicEnergy of Canada Limited Unpublished InternalReport, CRNL-1407. March 1976.

W.G. Cross - Canadian Progress Report to NEANDC.NEANDC(Can)49/L.

R.V. Osborne and N.W. Tepley - Tritium-in-Air Monitor.Canadian Patent, Registration No. 26,111.July 1976.

2.16 VERBAL PRESENTATIONS

A.R. Jones - Spent Fuel Monitor for Nuclear Safeguards.1976 Nuclear Science Symposium and Scintillationand Semiconductor Counter Symposium, 18-23October 1976.

A.R. Jones - A Versatile S>y Survey Meter with NumericalDisplay. 1976 Nuclear Science Symposium andSintillation and Semiconductor Counter Symposium,18-23 October 1976.

W.G. Cross and H. Ing - Spectra and Dosimetry ofTherapeutic Beams of Fast Neutrons in a WaterPhantom, Fourth Inter. Conf. on Medical Phys.,Ottawa, July 1976.

H. Ing and W.G. Cross - Calculated Leakage Spectra ofNeutrons Through Cu and Their Application to aSimulatec Criticality Accident, Annual Meetingof Health Physics Society, San Francisco, 28 Juneto 2 July 1976.

- 36 -

2.16.1 Local Talks

R.V. Osborne - Radioactivity, Radiation Physics andUnits, Health Physics Course at CRNL, 4-8 October1976.

R.V, Osborne - Tritium Monitoring, Health PhysicsInstrument Information Exchange at CRNL, 28-29September 1976.

A.R. Jones - Measurement of Radiation, Health PhysicsCourse at CRNL, 4-8 October 1976.

A.R. Jones - TLD and Personnel Dosimetry, HealthPhysics Instrument Information Exchange at CRNL,28-29 September 1976.

G. Cowper - Safeguards Instrumentation, Health PhysicsInstrument Information Exchange at CRNL, 28-29September 1976.

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ENVIRONMENTAL RESEARCH BRANCH

by

I.L. Ophel

3.1 Staff3.2 studies on Effects of Heated TVater on Aquatic Organisms3.3 Effects of Temperature on Algae3.4 interaction of Temperature and Toxic Chemicals on Algae3.5 Biochemistry and Microbial Ecology

3.5.1 Enzymological Assessment of DNA Repair - DeficientHuman Tissue Culture Cells

3.5.2 Biogeochemistry of the waste Management Area3.5.3 control Mechanisms in the Cellular Metabolism of

Ustilago Maydis3.6 Aquatic Radioecology and Freshwater Biology

3.6.1 Strontium-calcium Metabolism in Pish3.6.2 Role of Organic Matter in Perch Lake

3.7 St. Lawrence River Studies3.8 Perch Lake Project

3.8.1 Evaporat ion3.8.2 Chemistry3 9.3 Lysimeter Studies

3.9 Atmospheric Diffusion Study3.10 Snowmelt and Evapotranspiration in a Forested catchment3.11 Waste Management Area

3.11.1 Port Hope wastes3.11.2 waste Management Area B3.11.3 Perch Lake Basin3.11.4 Arsenic in Environmental samples3.11.5 Atomic Absorption Spectrophotometric Analysis of

Trace Elements

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3.12 Neutron Activation Analysis3.12.1 Ottawa River Bottom Sediments3.12.2 Perch Lake Basin Ground Water samples3.12.3 Cooperative study with Department of Earth

Sciences, University of Waterloo3.12.4 General

3.13 Cooperative Programs3.13.1 university of Waterloo3.13.2 Dispersivity Experiment3.13.3 Alberta Environment3.13.4 Agriculture Canada3.13.5 Canadian wildlife service3.13.6 Argonne National Laboratory, U.S.A.

3.14 Natural Nuclear Reactors in Canada3.15 Contaminant Hydrogeochemistry3.16 Isotopic Composition of precipitation Across Canada3.17 Atmospheric Dispersion of Tritiated water from CRNL

and NPD3.18 Natural Deuterium Concentrations in the Vicinity of

the La Prade Heavy water Plant3.19 Isotope Evaporation Studies3.20 Infiltration Studies on the East Side of Perch Lake Basin3.21 Low-Level Tritium Counting

3.21.1 Chemiluminescence3.21.2 Determination of Counting Efficiency

3.22 Environmental Impact Assessment3.23 Cesium-134 in Ottawa River Water3.24 Examination of Soil Samples from Port Hope, Ontario3.25 Monitoring of Land Gamma Background Radiation3.26 Gamma Exposure Rates at the CRNL Boundary3.27 Gamma Exposure Rates in the Exclusion Area3.28 Off-Site Monitoring3.29 Liquid Effluent Monitoring3.30 Liquid Disposal Area3.31 Tritium Survey3.32 Survey Summary3.33 Publications3=34 Verbal Presentations

3.34.1 Presented Papers3.34.2 Lectures or Seminars3.34.3 Local Talks

3.35 invited Speakers

For Figures 1, 2, 3 see end of Section

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3.1 STAFF

Branch Head - I.L. Ophel

Environmental Chemistry and Meteorology

P.J. Barry Assistants: P.C. JayR.E. LegereE. RobertsonD.P. wildsmith

L.K. Hendrie1

Natural isotope Studies

R.M. Brown Assistant: C D . Fraser

Biochemistry and Microbial Radioecology

D.R. Champ Assistant: J.L. Young

Radiochemistry and Terrestrial Radioecology

W.E. Grummitt Assistants: G. LahaieL.A. MaskH.M. McLaughlinW.J. Pierson

Contaminant Hydrogeochemistry

R.E. Jackson* Assistant: K.J. Inch3

1 Attached staff from Department of Geography, Univer-sity of Toronto, Ontario, Ontario, as of 4 October1976.

Directorate, Environment Canada, Ottawa, Ontario.

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3.1 STAFF (cont'd)

Biology and Aquatic Radioecoiogy

J.W. McMahon Assistants: A.E. DochertyS-R. Gentner

I.Ii. Ophel Assistant: J.M. Judd

Hydrology and Trace Element Analysis

W.F. Merritt Assistant: B.A. Risto

Secretarial

D.J. TerMarsch

3.2 STUDIES ON EFFECTS OF HEATED WATER ON AQUATICORGANISMS - J.W. McMahon and A.E. Docherty

Following completion of the experimental heatingfacility at Maskinonge Lake several weeks were devotedto resolving operational problems under winter condi-tions. These included control and maintenance of wa-ter lines and pumps; boiler fuel pump failures; lossof viscosity in the fuel oil and fabrication and in-stallation of the polyethylene enclosures in subzerotemperatures.

By mid-February the facility was operating sat-isfactorily and studies were initiated to assess;(1) seasonal effects of thermal enrichment on phyto-plankton production succession and populations, and(2) effects of depth of intake and discharge of cool-ing water on plankton organisms.

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3.2 STUDIES ON EFFECTS OF HEATED WATER ON AQUATICORGANISMS (cont'd)

Data for the seasonal succession experiment coversearly spring (prior to ice removal on the lake), spring,summer and fall. Lack of finances for boiler fuel pre-vented us from obtaining the data under winter condi-tions.

Studies on effects of different intake and dis-charge depths covered the following situations: surfaceintake and discharge; deep intake and discharge; deepintake, surface discharge. Phytoplankton primary pro-ductivity, species composition and numbers were deter-mined twice-weekly at selected depths in the experimen-tal column, a non-heated control column and in the lake.Temperature, dissolved oxygen concentration, total in-organic carbon, total phosphorus and pH were also moni-tored, plankton samples were also prepared and storedfor measurement of adenosine triphosphate (ATP) usingthe firefly extract (luciferinrluciferase) technique.Analyses for ATP are currently in progress.

Results show that a deep intake combined with asurface discharge results in a minimum increase in tem-perature and biomass in the receiving water body.

3.3 EFFECTS OF TEMPERATURE ON ALGAE - J.W. McMahon and S-R.Gentner

Studies on the optimal temperatures for maximumgrowth in pure cultures of green algae are currentlyin progress. These laboratory experiments are designedto assess the effect of different temperatures, underfixed lighting conditions, on growth (numbers of organ-isms) and *4C primary production of various algaespecies.

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3.4 INTERACTION OF TEMPERATURE AND TOXIC CHEMICALS ON ALGAE- J.W. McMahon and S-R. Gentner

During the year a study was carried out on a poly-chlorinated biphenyl (Arochlor 1242) and its effectson unicellular green algae. PCB concentrations greaterthan 0.133 ppm inhibited algae growth while 0.33 ppmwas lethal for the alga coelastrum microporum within a24-hour period. Ankistrodesmus braunii exhibited nor-mal growth curves in concentration of 0.05, 0.07 and0.1 ppm.

The volatile nature of PCB's coupled with problemsin quantitative extraction (formation of emulsions)make them extremely difficult to work with. In addi-tion, the quantitative measurement of extracted PCB'susing gas chromatography electron capture techniqueswas hampered by appearance of unrelated peaks in thechromatograms of Arochlor 1242 and the unreliability ofcommercially prepared chromatographic columns.

3.5 BIOCHEMISTRY AND MICROBIAL ECOLOGY

3.5.1 Enzymoloqical Assessment of DNA Repair - Deficient HumanTissue Culture Cells - D.R. Champ, J.L. Young and S.M.Marko

In a joint program with M.C. Paterson (BiologyBranch) we have endeavoured to elucidate the nature ofthe biochemical defect in cells cultured from humanssuffering from Ataxia Telangiectasia (AT), a conditionwhich results in sensitivity to gamma radiation. Studiesby M.C. Paterson had indicated a probable deficiency inan endonuclease activity (gamma endonuclease) which isrequired in the excision repair process on gamma ir-radiated DNA. Demonstration of the postulated deficiencyrested upon the isolation of the enzyme from cells fromcontrol patients and the subsequent demonstration of re-duced levels of the enzyme in cells from AT patients.

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3.5.1 Enzymological Assessment of DNA Repair - DeficientHuman Tissue Culture Cells (cont'd)

Our approach has been to try to develop a purifica-tion procedure for the putative enzyme using chickembryca as a model system. Two assays for the endonu-clease have been employed, both test for preferentialinteraction of the extracts with gamma irradiated DNAversus unirradiated DNA. The first, a relatively rapidbut indirect assay, looked for the presence of enzymeswhich would bind to DNA on the assumption that the gammaendonuclease would not only break the DNA but also as-sociate strongly with it. The second assay measureddirectly the ability to break gamma irradiated DNA ie-lative to non-irradiated DNA.

Initially we demonstrated the presence of a gammaendonuclease in cell-free extracts from fibroblastcells cultured from "normal" patients. Prom smallquantities of cells, 4 x 10 , cell-free extracts con-taining approximately 11 mg of soluble protein wereprepared. These extracts were found to catalyze theintroduction of single-strand breaks into fibroblastDNA gamma irradiated (jln vivo) versus unirradiated DNA.These studies have shown that cultured human fibroblastcells derived from "normal" patients do indeed containan endonuclease activity that cleaves DNA specificallyat sites which have arisen as a result of gamma ir-radiation.

Twelve-day-old chick embryos were dissected,homogenized and ultrasonically disrupted to produce cell-freeextracts. These cell-free extracts were treated withstreptomycin sulfate to remove nucleic acids and theresidual protein solution was fractionated on bothanionic and cationic exchange resins. The fractionsafter each treatment were examined for gamma endonu-clease activity by both assay systems. We were ableto demonstrate the presence of an endonuclease specificfor gamma irradiation damage in DNA and to follow it

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3.5.1 Enzymological Assessment of DNA Repair - DeficientHuman Tissue Culture cells (cont'd)

through several purification steps. However, our assaysystem for examining for direct breakage has proven notsufficiently sensitive and to possess too high a back-ground of non-specific DNA breaks. Therefore, we havebeen unable to examine the kinetics of DNA breakagewith our fractions, a prerequisite for demonstratingthat the purification procedure is indeed useful.

Cell-free extracts have also been prepared fromAT cells and have been shown to possess gamma endonu-clease activity on DNA purified from cells gamma ir-radiated under anoxic conditions. Therefore, AT cellsare not totally devoid of the gamma endonucxease. Theassays do suggest that the levels of activity in ATextracts may be somewhat less than "control" extracts.However, we have been unable to quantify the differencedue to the insensitivity of the assay as noted pre-viously.

Further efforts, by our laboratory, at elucidat-ing the nature of the biochemical defect in AT cellsare not planned, at least for the immediate future.

3.5.2 Biogeochemistry of the waste Management Area - D.R.Champ and J.L. Young

A joint program with R.E. Jackson (EnvironmentCanada) and J. Gulens (General chemistry Branch) toexamine oxidation-reduction processes in ground waterflow systems was initiated during the past year. Ithas been observed by us as well as others that themeasured potential of ground water in a confined aqui-fer decreases as it migrates from upland, rechargeareas to lowland, discharge areas. We have proposed amodel consisting of a sequence of microbially catalyzedredox reactions to account for this observation. Thesereactions predict certain trends in the concentrationof various inorganic and organic components in the

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3.5.2 Biogeochemistry of the Waste Management (cont'd)

system and we are currently testing these predictions.As an initial survey, measurements have been made atfour points along the CRNL waste management area groundwater flow system. These have included field measure-ments of ground water pH, E H (the measured Pt electrodepotential), temperature, specific conductance, DO (dis-solved oxygen) and sulfide as well as laboratory mea-surements of nitrate, sulfate, alkalinity, silica,iron and manganese. During the fall a carbon analyzerwas installed in our laboratory and this instrumenthas been extensively tested and used to determine bothorganic and inorganic carbon concentrations in theground water samples. Concentrations in the range of1 to 4 ppm for organic c and 6 to 2 5 ppm for inorganicC have been observed.

The above studies are continuing and it is ex-pected to monitor two of the hydrology network piezo-meters throughout the winter to determine if a sea-sonal variation occurs due to the absence of rechargeduring the winter months.

3.5.3 Control Mechanisms in the Cellular Metabolism ofUstilago Maydis - D.R. Champ and J.L. Young

Tn a joint program with P. Unrau (Biology Branch)we are currently characterizing a novel class of pro-teins, from the smut fungus Ustilago Maydis, which maypossess a control function in DNA repair as well asother cellular processes. The occurrence of this classof proteins in other organisms is also being investi-gated, i

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3.6 AQUATIC RADIOECOLOGY AND FRESHWATER BIOLOfff

3.6.1 Strontium-Calcium Metabolism in Fish - I.L. Ophel andJ.M. Judd

Experiments dealing with the biological half-livesof both ^5gr an

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3.6.2 Role of Organic Matter in Perch Lake (cont'd)

1969) is used for cation exchange and fixation capaci-ties. Sediment cation exchange capacity (CEC) is deter-mined by a 60co chloride saturation procedure. Fixa-tion capacity is then determined by washing the CEC sam-ple in 1 N ammonium chloride solution and recountingfor 60co# Stable elements are assayed using atomic ab-sorption and flame emission spectroscopy.

Three ponds were constructed at Perch Lake mainstation during the summer. Two of these (8 m and 5 mdia.) are for experimental work using radioisotopes tolabel organic detritus and the third pond (10 m dia.)is for use by P.J. Barry in evaporative studies. Thetwo smaller ponds were planted with common aquaticplants obtained directly from Perch Lake. The plantsgrew well and appear to have established themselvesbefore the winter freeze-up.

3.7 ST. LAWRENCE RIVER STUDIES - I.L. Ophel

The group from the Universite du Quebec a Trois-Rivieres has continued a study on the effects of heatedwater discharged by Gentilly Nuclear Generating Stationand the La prade Heavy water Plant (under construction)on the biota of the St. Lawrence River. Their contractresearch (including other studies on water chemistry,sediments, fish and wildlife) is coordinated by a com-mittee of personnel from Environment Canada, Hydro-Quebecand AECL. Studies funded by AECL in 1976 were concernedmainly with the distribution and population structureof benthic organisms and the ecology of aquatic plantcommunities.

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3.8 PERCH LAKE PROJECT

3.8.1 Evaporation - P.J. Barry and E. Robertson

During 1976, energy budget and evaporation studieswere extended to include Maskinonge and Upper BassLakes. The object in to relate turbulent diffusivityof lakes to wind speed, lake size and water quality.Such, information is needed in connection with studieson the fate of waste heat discharged into water bodiesand in the distribution of radioactive and other chemi-cal substances in lakes.

At Perch Lake three temperature probes were posi-tioned at points equidistant from each other in thearea where the lake is 3.5 m deep in the hope that aver-age temperatures at each depth would enable effects ofadvection to be averaged out. However, due to elec-tronic problems and loss of several platinum resistancebulbs during thunderstorms much data was lost. Re-calibration of the bulbs in the laboratory in Novemberindicates that there were small current leaks from thecables. The data is being validated by comparison withmanual readings. These were done regularly with athermistor on a measured cable. A probe fitted witheight thermistors was positioned permanently in the sed-iments at the centre of the lake. Temperatures weretaken once a week to a depth of 200 cm below the sedi-ment water interface.

At Maskinonge Lake,temperature profiles were takenregularly from the beginning of May with the portablethermistor probe. A net radiometer was installed on araft at the centre of the .1=Oce but the portable battery-operated recorder did not prove satisfactory under fieldconditions. Temperature profiles were also taken Ee-gularly at the centra of Upper Bass Lake from earlyJuly until freeze-up.

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3-8.1 Evaporation (cont'd)

Evaporation rates have been calculated for thethree lakes. For upper Bass Lake values of net radia-tion and Bowen Ratio from Perch Lake were used. ForMaskinonge Lake the Perch Lake net radiation was ad-justed for the difference in water surface temperaturebetween the two lakes. This is significant in May andOctober. The Bowen Ratio for Maskinonge Lake was cal-culated from temperatures and relative humidities ob-served on a raft on the lake.

The results indicate that the only terra of theenergy budget equation that varies significantly forthe three lakes is the change in heat storage. Overthe whole ice-free period the total eveiporation fromthe three lakes is nearly the same.

Evaporation pan experiments done in cooperationwith the Atmospheric Environment Service were also ex-tended to Maskinonge Lake. A pair of class "A" evapora-tion pans, one submerged to within 7.6 cm of itsrim and the other raised on a platform, were installedat the centre of both Perch and Maskinonge Lakes. AtMaskinonge Lake the pan assembly was protected fromwaves by a double set of booms, with these precautionsonly about ten day's data was lost due to spilling ofwater from the pans. A third pan for isotope studieswas operated from the raft on Maskinonge Lake in cooper-ation with R.M. Brown.

3.8.2 Chemistry - P.J. Barry and P.c. Jay

Tritium analyses of weekly water samples fromPerch Lake Outlet, Perch creek Weir and No. 1 and No. 2Inlets were continued.

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3.8.2 Chemistry (cont'd)

Weekly measurements of lake dissolved oxygen werecontinued up to 9 November when the lake became icecovered. The method of sampling lake water at differ-ent depths for iron and manganese analysis proved to beunsatisfactory. As the water sample was exposed to theair some of the manganese and iron was oxidized to ahigher state of oxidation and precipitated out beforeanalysis. A new method of sampling has now been adoptedfor next spring in which the water sample will not beexposed to air before analysis.

The chemical budgets for four major ions in PerchI-"Tea are now nearing completion and the results are be-ing prepared for publication.

Analysis of seepage meter water samples for tritiumis continuing in cooperation with D.R. Lee, Universityof Waterloo. Further chemical analyses have been doneon the same samples for Mn, Pe and K by atomic absorp-tion spectrophotometry. It was noted that ground waterseepage under the dike and into Perch Lake is more im-portant than first suspected. By observing open waterholes alor>g the dike where the lake surface was late infreezing and taking samples of water directly from theseareas it was found that the tritium content of the waterwas much higher than the main body of lake water.

Analysis of leaf samples from experimental plotsis now being done in cooperation with L.K. Hendrie,University of Toronto. The concentration of Mn and Pein the leaf samples is very high. More analyses ofthese samples will be done later.

A i m section of an 8 m sediment core taken fromPerch Lake in late summer was cut into 2 cm slices forchemical analysis. It was found that the equipmentused to section the core needed improvements when handl-ing the more fluid portions of the core and the neces-sary modifications were made.

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3-8.3 Lysimeter Studies - P.J. Barry and R.E. Legere

The 1-8 m diameter floating lysimeter at the ex-perimental field was calibrated during the period, itis to be used this winter to measure evaporation fromsnow. Calibration proved to be difficult and althoughthe problems were eventually overcome the causes arestill not understood. In subsequent tests duringSeptember and October, precipitation measured with astandard rain gauge agreed very well with that obtainedby the lysimeter. This observation gives some confi-dence that the calibration problems were successfullyovercome. The lysimeter was completely covered withsnow by the beginning of December and the first recordswere being analyzed for evaporation by the end of theyear.

3.9 ATMOSPHERIC DIFFUSION STUDY - P.J. Barry and D.P.Wildsmith

Routine observations continued during the year.

3.10 SNOWMELT AND EVAPOTRANSPIRATION IN A FORESTED CATCH-MENT - L.K. Hendrie, G. Szeicz and R.E. Legere

This project is designed to investigate the waterbalance of a forested catchment. Although prime em-phasis is being placed upon the radiative exchanges in-volved in the snowmelt process and the evapotranspira-tional process during the warmer months, other relevantparameters will also be considered. The measurementsite selected is in aspen-birch-maple forest on thesoutheast side of Perch Lake, and adjacent to the PerchLake Satellite Station.

Following preliminary surveys of the area inJanuary and June 1976, concexitrated on-site prepara-tions for the project commenced in October 1976.Radiometers have been designed and constructed to

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3.10 SNOWMELT AND EVAPOTRANSPIRATION IN A FORESTED CATCH-MENT (cont' d)

permit the monitoring of net radiation and the attenua-tion of the solar beam through the forest layers. Toimprove the representativeness of the sampling of thisparameter in such a complex radiative environment,these instruments have been constructed with 1 m longsensing units rather than the conventional small discsensors of 1 to 2 cm across. The solarimeters werebuilt according to the design of Szeicz, Monteith andDos Santos (J. Applied Ecology 1, pp. 169-174, 1964),with so