90Sr IN VARIOUS FOOD AND FOODSTUFFS

U. Repinc, L. Benedik, R. Jakopic

Department of Environmental Sciences

Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, SLOVENIA

Isotopic and Nuclear Analytical Techniques for Health and Environment 10 - 13 June 2003, Vienna, Austria

Major pathways of radionuclides to man

Radionuclides of interest

- produced in fission processes which may contribute significantly to human exposure

Characteristics of strontium

89Sr (t1/2 = 50.5 d, Emax = 1.49 MeV) 89Y (stable)

IIA. Group of the Periodic Table

90Sr (t1/2 = 28.7 y, Emax = 0.546 MeV)

90Y (t1/2 = 64.1h, Emax = 2.28 MeV)

90 Zr (stable)

-chemically similar to calcium

-20-30% of absorbed Sr is deposited in the bone, 1% is distributed among the blood volume, extracellular fluid, soft tissue, and surface of the bone

-internal exposure to Sr-90 is linked to bone cancer, cancer of the soft tissue near the bone and leukemia

is considered one of the most hazardous fission products:

- high fission yield

- has a long physical half-life (28.7 years)

- has a long biological half-life (49.3 years)

- high radiotoxicity due to its tendency to deposit in bones

is one of the main component of fallout activity after an accident:

- high fission yield

- relatively short-lived (50.5 days), decays to undetectable levels in a few months

- it is not considered as hazardous as 90Sr

90Sr

89Sr

Food sampling

- individual food items, not total diet samples (to indicate which countermeasures should be taken to reduce population exposure)

- radionuclides most likely to be present in terrestrial food and environment

or can be rapidly accumulated by fresh water or marine organisms like oysters, clams, shrimp, etc.

Samples selected

- foodstuffs for infants

milk powder, fruit milk mash,

infant milk, wheat flakes

- eggs: whites and yolk

- sea food

golden grey mullet, gilthead seabream, European anchovy, mussels

- meat (beef)

- freshwater fish: trout

- vegetables: cabbage, potato

sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl

filtrat ionaddition of oxalic acid

NaOH to pH 4-5oxalate precipitation

dissolution in HNO3

fuming HNO3 separation (2 times or more)nitrate precipitation

dissolution in deionized water

addition of Ba-carrieraddition of Fe-carrier

NH4 OHhydroxide precipitation

addition of NH4COOCH3

(NH4)2CrO4

CH3 COOHchromate precipitation

addition of (NH4)2 CO3

SrCO3 precipitation

beta measurement of 90Sr, 89Sr and 90 Y

centrifugation

centrifugation

filtration black belt filter paper

filtration black belt filter paper

discard precipitate

discard precipitate

discard solution

discard solution

discard solution

sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl

filtrat ionaddition of oxalic acid

NaOH to pH 4-5oxalate precipitation

dissolution in HNO3

fuming HNO3 separation (2 times or more)nitrate precipitation

dissolution in deionized water

addition of Ba-carrieraddition of Fe-carrier

NH4 OHhydroxide precipitation

addition of NH4COOCH3

(NH4)2CrO4

CH3 COOHchromate precipitation

addition of (NH4)2 CO3

SrCO3 precipitation

beta measurement of 90Sr, 89Sr and 90 Y

centrifugation

centrifugation

filtration black belt filter paper

filtration black belt filter paper

discard precipitate

discard precipitate

discard solution

discard solution

discard solution

Strontium separation procedure

K and Si removalpreconcentration of alkaline elements

separation of strontium and calcium

removal of Fe, Al

Ca removal

Strontium separation procedure – cont.

sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl

filtrat ionaddition of oxalic acid

NaOH to pH 4-5oxalate precipitation

dissolution in HNO3

fuming HNO3 separation (2 times or more)nitrate precipitatation

dissolution in deionized water

addition of Ba-carrieraddition of Fe-carrier

NH4 OHhydroxide precipitation

addition of NH4COOCH3

(NH4)2CrO4

CH3 COOHchromate precipitation

addition of (NH4)2 CO3

SrCO3 precipitation

beta mesurement of 90Sr, 89Sr and 90 Y

centrifugation

centrifugation

filtration black belt filter paper

filtration black belt filter paper

discard precipitate

discard precipitate

discard solution

discard solution

discard solution

sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl

filtrat ionaddition of oxalic acid

NaOH to pH 4-5oxalate precipitation

dissolution in HNO3

fuming HNO3 separation (2 times or more)nitrate precipitatation

dissolution in deionized water

addition of Ba-carrieraddition of Fe-carrier

NH4 OHhydroxide precipitation

addition of NH4COOCH3

(NH4)2CrO4

CH3 COOHchromate precipitation

addition of (NH4)2 CO3

SrCO3 precipitation

beta mesurement of 90Sr, 89Sr and 90 Y

centrifugation

centrifugation

filtration black belt filter paper

filtration black belt filter paper

discard precipitate

discard precipitate

discard solution

discard solution

discard solution

removal of Ba, Ra, Pb

centrifugation on 22 mm diameter planchette, drying

determination of the chemical yield by weighing SrCO3

measurement of 89Sr, 90Sr/90Y on beta counter

Beta counting

A multilogger LB 5310 low-level gas proportional counter

(Berthold Inc., Bad Wildbad, Germany)

- 22 mm diameter planchettes - calibrated with 90Sr/90Y standard

17% counting efficiency, 90Sr 43% counting efficiency, 90Y

A - 90Sr activity in the sample, Bq/kg

R - count rate of the sample (without background), cpm

Rs+b -count rate of the sample and background, cpm

Rb – background count rate, cpm

ts – measuring time, sample

tb – measuring time, background

YSr – chemical yield of the separation

Sr-90 - counting efficiency for 90Sr

Y-90 – counting efficiency for 90Y

m - sample weight (kg)

h – decay constant for 90Y (1.8022E-4 min-1)

t – ingrowth time from separation of 90Sr to counting (min)

90Sr activity calculation

ResultsTABLE I. RESULTS OF 90Sr DETERMINATION IN SELECTED FOOD AND FOODSTUFF SAMPLES,

Bq/kg FRESH WEIGHT

TABLE II. RESULTS FOR 90Sr IN FRESHWATER FISH SAMPLES, INCLUDED IN THE KRŠKO NPP MONITORING PROGRAMME

TABLE III. RESULTS OF Sr-90 DETERMINATION IN SELECTED FOOD AND FOODSTUFF SAMPLES,

Bq/kg FRESH WEIGHT

TABLE IV. COUNCIL REGULATION (EURATOM) NO.3954/87 OF 22 DECEMBER 1987

• activity concentrations in selected food and foodstuff samples are low

(below detectable 0.01 to 0.9 Bq/kg 90Sr)

• activity concentrations in selected food and foodstuff samples are below maximum permitted levels of radioactive contamination laid down in EU regulations

• no significant differences in freshwater fish samples from the vicinity of

NPP Krško could be observed due to the operation of NPP

• results confirm that selected food and foodstuffs do not represent a health hazard to the population

Conclusions