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RASCAL 4.1 Radiological Assessment System for Consequence Analysis
RASCAL 4.1 National Radiological Emergency
Preparedness Conference Tuesday, April 19, 2011
Lou Brandon
NRC Radiological Assessment Code for Consequence Analysis (RASCAL) Version 4.1:
Updates, Perspectives, Initiatives, Resources, and Future Plans
• Version 4.0 released in June 2010 • Version 4.1 released in January 2011 • Presentation goals:
– Highlight the changes and new features – Discuss in more detail big changes – Discuss the ongoing and future work on RASCAL
Atmospheric Dispersion
• What is New? – RASCAL v4 has changed from distance-based
dispersion parameters to time-based parameters – Gone are the Pasquill-Gifford parameters – Dispersion is now a function of:
• time since release • wind speed • atmospheric stability • surface roughness
Atmospheric Dispersion – most significant change
• What are the Implications of the Changes? – The RASCAL v4 dispersion parameters tend to be
larger than the RASCAL v3.0.5 parameters – X/Qs and doses for ground-level releases will tend
to be lower – X/Qs and doses for elevated releases will tend to
be higher near the release point
Atmospheric Dispersion
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
0.1 1 10To
tal E
DE
(rem
) Distance (mi)
R3 Plume
R3 Puff
R4 Plume
R4 Puff
1.E-02
1.E-01
1.E+00
1.E+01
0.1 1 10
Tota
l ED
E (r
em)
Distance (mi)
R3 Plume
R3 Puff
R4 Plume
R4 Puff
Ground Level, D Stability, 3 m/s
Elevated, D Stability, 3 m/s
Conditions Ratio R4/R305 for thyroid dose at 5 miles
4 mph, D stability 27%
15 mph, B stability 31%
4 mph, G stability 16%
8 mph, D stability, Rain 24%
Model differences in thyroid doses for a core uncovered scenario with differing met conditions
3.0.5 (left) vs 4.0 TEDE 3.9 rem vs 1.2 rem at 2 mi
1.3 rem vs 0.38 at 5 mi
9
8 mph, E Stability
TEDE > 1 rem at 5 miles
TEDE > 1 rem at 2 miles
• Are the Dispersion and Deposition Changes Reasonable? – Regional Atmospheric Transport Code for Hanford
Emissions (RATCHET) developed in 1990s, now in RASCAL – The Hanford Environmental Dose Reconstruction Project
included an extensive validation effort – The development and application of the new algorithms
were extensively reviewed by leading experts including F. Gifford and scientific organizations including the National Academy of Sciences.
– The dispersion and deposition algorithms have been used in subsequent dose reconstruction projects (ORNL, INEL, Rocky Flats, and Mayak, USSR)
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Atmospheric Transport & Dispersion (ATD)
Rocky Flats – Sulfur Hexafluoride Tracer Study
• Evaluation of Atmospheric Transport Models for Use in Phase II of the Historical Public Exposure Studies at the Rocky Flats Plant (Risk Analysis, Vol 19, No. 4, 1999, Rood, Killough, Till)
• Involved 5 models; ISCST2, RATCHET, TRIAD, INPUFF2, and TRAC.
• “No one model outperformed the others in all modeling objectives… …overall performance of RATCHET was somewhat better than the other models.”
Atmospheric Deposition
• Why the Changes? – The RASCAL v3.0.5 parameters were developed
in the 1950s and early 1960s. – Research on atmospheric processes in the 1960s,
1970s, and 1980s provide better methods of estimating atmospheric deposition.
Atmospheric Dry Deposition
• What is New? – RASCAL v4 has changed from constant dry
deposition velocities to dry deposition velocities that are a function of atmospheric conditions including wind speed, stability, and surface roughness.
– RASCAL v4 treats iodine (halogens) as three species having different deposition characteristics for purposes of calculating deposition (I2, particles, and CH3I)
Atmospheric Dry and Wet Deposition
• What is New? – RASCAL v4 iodine speciation is 25% Particles,
30% I2, and 45% CH3I; CH3I is assumed not to deposit.
– RASCAL v4 uses a wet deposition velocity for wet deposition of gases and a washout model for wet deposition of particles. These parameters are functions of wind speed, atmospheric stability, surface roughness, and precipitation rate
Atmospheric Deposition
• What are the Implications of the Changes? – The RASCAL v4 deposition parameters, while not
constant, tend to be within a factor of 2 of the RASCAL v3.0.5 parameters.
– RASCAL v4 deposition velocities for iodine tend to be lower than the RASCAL 3.0.5 value in low wind speed conditions and higher in high wind speeds.
– Deposition of iodine is generally lower in RASCAL v4 because 45% of the iodine does not deposit.
Updated Core Inventory
• Old core inventory – RASCAL 3 – Taken from NUREG-1228 / WASH-1400 – Selected for early health effects + likely noble
gases
• New core inventory – RASCAL 4 – Based on normalized SCALE/ORIGEN run – Increased number of nuclides from 33 to 58 – No longer select for early health effects
• Impact – small changes to source term
Updated Coolant Inventory
• From ANSI/ANS 18.1-1999 • Old inventory (RASCAL 3) excluded:
– nuclides with half-life < 50 minutes, and – noble gases for BWRs
• New inventory (RASCAL 4) includes all • A more complete set; nuclide number
increased from 36 to 63 • Impact – small changes to source term
Radioactive Decay: What Is New?
• The decay scheme has been revised in the source term, environmental and dose calculations
• The decay scheme uses simplified chains that include short-lived daughters implicitly and are truncated at long-lived daughters
• Decay calculations are made using the Bateman Equations for 0 to 3 daughters and include branching.
• Nuclides with implicit daughters have a ‘*’ after the name; e.g. Cs-137*
Radioactive Decay
• Why the Change? – Consistency
• RASCAL v3.0.5 uses 3 different decay schemes • RASCAL v 4 uses just one
– Traceability • RASCAL v4 decay schemes are documented • Appendices in the technical documentation list the
chains, decay parameters and implicit daughters
Radioactive Decay
• What are the Implications of the Change?
– The changes in decay schemes should not result in any significant changes in dose estimates; however, they significantly alter DRL estimates.
– Truncation errors have been evaluated and are generally << 1%
– Addition of implicit daughters and simplification of chains that include branching increases doses slightly at short times
Monitored Release
• Assumptions – Monitored pathway – Monitor capable of distinguishing between
particle and noble gas activity – Reactor is shutdown with core damage – Particles are CsI
Monitored Release
• Why the Change? – RASCAL 3.0.5 significantly overestimated the
long-term consequences of a release by exaggerating the Cs-137 activity
– RASCAL 3.0.5 significantly underestimated the short-term consequences of a release by minimizing the I-131 activity
Monitored Release
Isotope RASCAL v3.0.5 RASCAL v4
I-131 0.500 0.115
I-132 0.167
I-133 0.233
I-134 0.258
I-135 0.223
Cs-134 0.00193
Cs-136 0.000613
Cs-137 0.500 0.00134
Monitored Release Particle Activity Fraction
Changes in SF Pool
• New version requires only age of newest batch, total batch count, and times for cooling lost and regained
• Assumes a 18 month refuel interval and cladding fire if not cooled for 2 hours
• Release over 24 hours unless re-cooled • Impact – generally smaller source terms due to
better characterization of newest batch
Intermediate Phase Doses
• Have been added to the Source Term to Dose model; previously only in Field Measurement to Dose
• Based on the projected deposition • Allows early “look” as relocation issues
IP Doses Available in 2 Places
Maximum Values Summary Detailed Results
Values provided for any location.
Millstone – Thyroid CDE 5.6 rem @ 0.2 mi
This is a low dose impact scenario with PAGs exceeded less than 0.25 miles out.
FDA DRL 9600 pCi/m2 (prod) ~ 0.01 uCi/m2
So, DIL possibly exceeded beyond 50 miles. Sample before embargoing.
Lowest RASCAL scale now about I-131 DRL limit for produce.
Export Footprint to Shapefile
• Shapefile is a geospatial vector file format • Export function requires the MapWindow GIS
open source software • www.mapwindow.org • Separate installation required for this feature
to work • MapWinGIS installer available with RASCAL
installation
Advantages of Plume in GIS
• Can perform spatial analysis; answer questions about geographic features in relation to the plume
• Have more control over the display – Emphasize features of interest – Add or subtract layers,i.e. change background
• Plot other information such as field team readings
Use the conversion tool “Layer to KML” in the ArcToolbox Create a file from the “plume” layer Drag the new file into Google Earth
ArcMap to Google Earth
Release Rate Calculations
Gross concentration and flow rate are used to calculate a release rate in the units specified on the previous screen. The is a “one-way” tool. It only inserts the calculated value. Nothing is saved.
DRD Correction Factor Assist field teams by developing a correction factor for direct reading dosimeters that will estimate internal dose
Gamma Rate
3 hours since release 2 miles downwind 15 minute DRD correction factor is 1.2. Low impact on total dose.
Gamma Rate 2
1.5 hours since release 2 miles downwind 15 minute DRD correction factor is 13.5. High impact on total dose.
DRD CF Summary
• If radionuclide mix in plume includes particulates, internal dose impact is from more than just iodines.
• DRD readings may need to be corrected by factors as high as 20.
• KI has much more limited effectiveness because it doesn’t limit dose, other than to thyroid.
• For various scenarios, dose and KI effectiveness for public populations, evacuating or stationary, can be analyzed.
Improved Interpolation of Meteorological Obs and Fcst
• Now interpolate between observations and forecasts; smoother transitions
• Persist both observations and forecasts for up to 2 hours, then interpolate
• Warn if asked to interpolate wind direction shift > 90 deg
• Warn if forecasts will be deleted
Calm Wind Modeling
• Calm wind model used for close-in calculations updated to improve consistency.
• Dispersion is a function of time after release. • If release stops, model will continue to
calculate doses and deposition. • Under calm conditions, wind speed not
extrapolated to release height.
Verification and Validation
• Work is ongoing in both areas • Examples shown for TurboFRMAC and NARAC
FMDose / TurboFRMAC
• FRMAC Assessment Workgroup • Compared results from RASCAL 4.0 & 4.1
Field Measurement to Dose model with TurboFRMAC 2010
• Found good agreement • Work ongoing • FRMAC proposing changes to resuspension
methods; RASCAL may follow
Figure 7.1 Comparison of Intermediate Phase TEDE Estimates From RASCAL 4 and TurboFRMAC2009 for Ground Contamination of 103 μCi/m2 for 25 Isotopes.
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04
RASC
AL 4
TED
E
TurboFRMAC TEDE
1st Year
50 year
2nd Year
Figure 7.2 Comparison of Intermediate Phase Exposure Rate DRL Estimates From RASCAL 4 and TurboFRMAC2009 for Ground Contamination of 103 μCi/m2 for 25
Isotopes
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04
RASC
AL 4
Dos
e Ra
te D
RL
TurboFRMAC Dose Rate DRL
1st Year
50 year
2nd Year
Table 7.2 Intermediate Phase Dose Radionuclide Exposure Period RASCAL 4 Turbo FRMAC 2009 Spreadsheet I-132 First Year 0.0801 0.0816 8.00E-2 Second Year NC NC NC Fifty Years 0.0801 0.0816 8.00E-2 Sr-90 First Year 0.679 0.689 NC Second Year 0.428 0.427 NC Fifty Years 8.16 8.16 NC Sr-90 + Y-90 First Year 0.685 NC NC Second Year 0.428 NC NC Fifty Years 8.17 NC NC Sr-90+ First Year 0.684 0.689 NC Second Year 0.428 0.427 NC Fifty Years 8.16 8.16 NC Am-241 First Year 70.2 71.9 70.2 Second Year 8.86 8.84 8.88 Fifty Years 297 2.98 306 I-129 First Year 2.29 2.23 2.29 Second Year 1.95 1.90 1.95 Fifty Years 55.5 54.0 55.1 U-232 First Year 103 104 NC Second Year 12.2 10.3 NC Fifty Years 425 323 NC U-232- First Year 100 104 NC Second Year 10.0 10.3 NC Fifty Years 313 323 NC
(rem) TF2010 R2
0.570 0.423 8.02
72.2 8.86
2.99E2 2.23 1.90 54.4
Based on 1000 uCi/m2 deposition
Table 7.3 Dose (exposure) Rate DRL Radionuclide Exposure Period RASCAL 4 Turbo FRMAC
2009 FRMAC Manual
2003
Spreadsheet
I-132 First Year 861 862 853 862 Second Year NC NC NC NC Fifty Years 2150 2160 2130 2150 Sr-90 First Year 3.99E-2 2.54E-1 3.04E-2 NC Second Year 4.57E-2 1.02E-1 3.96E-2 NC Fifty Years 2.48E-2 5.34E-2 1.46E-2 NC Sr-90 + Y-90 First Year 7.68E-1 NC NC NC Second Year 4.57E-1 NC NC NC Fifty Years 4.87E-1 NC NC NC Sr-90+ First Year 2.55E-1 2.53E-1 NC NC Second Year 8.42e-2 8.40E-2 NC NC Fifty Years 5.35e-2 5.33E-2 NC NC Am-241 First Year 1.22E-2 1.06E-2 9.25E-3 1.22E-2 Second Year 2.04E-2 1.82E-2 1.68E-2 2.04E-2 Fifty Years 7.22E-3 6.39E-3 4.51E-3 7.02E-3 I-129 First Year 3.52E-1 3.52E-1 3.24E-1 3.52E-1 Second Year 8.70E-2 1.03E-1 8.10E-2 8.70E-2 Fifty Years 3.63E-2 363E-2 1.55E-2 3.65E-2 U-232 First Year 6.37E-5 3.35E-4 NC NC Second Year 7.29E-6 7.00E-4 NC NC Fifty Years 1.69E-6 2.68E-4 NC NC U-232- First Year 3.14E-4 3.35E-4 NC NC Second Year 6.57E-4 7.00E-4 NC NC Fifty Years 2.52E-4 2.68E-4 NC NC
mR/h TF
2010 R2
1.05E-2 2.15E-2 6.38E-3 3.51E-1 1.03E-1 3.60E-2
Table 7.4 Marker Radionuclide DRL Radionuclide Exposure Period RASCAL Turbo FRMAC
2009 FRMAC Manual
2003
Spreadsheet
I-132 First Year 2.50E4 2.50E4 2.94E4 2.50E4 Second Year NC NC NC NC Fifty Years 6.24E4 6.24E4 7.35E4 6.25E4 Sr-90 First Year 9.00E3 2.90E3 8.00E3 NC Second Year 1.03E4 9.65E2 1.04E4 NC Fifty Years 5.59E3 6.12E2 3.85E3 NC Sr-90 + Y-90 First Year 8.78E3 NC NC NC Second Year 1.03E4 NC NC NC Fifty Years 5.57E3 NC NC NC Sr-90+ First Year 2.92E3 2.90E3 NC NC Second Year 9.62E2 9.65E2 NC NC Fifty Years 6.14E2 6.12E2 NC NC Am-241 First Year 28.4 27.8 25.0 28.5 Second Year 47.6 47.7 45.5 47.5 Fifty Years 16.8 16.8 12.2 16.4 I-129 First Year 8.73E2 8.73E2 9.52E2 8.74E2 Second Year 2.16E2 2.56E2 2.38E2 2.16E2 Fifty Years 9.00E1 9.00E1 4.55E1 9.08E1 U-232 First Year 4.03 19.3 NC NC Second Year 4.62E-1 40.4 NC NC Fifty Years 1.07E-1 15.5 NC NC U-232- First Year 19.9 19.3 NC NC Second Year 41.6 40.4 NC NC Fifty Years 16.0 15.5 NC NC
uCi/m2 TF
2010 R2
2.44E4
NC
6.10E4
2.90E3
1.17E3
6.12E2
27.7
56.4
16.7
897E2
2.63E2
91.9
TurboFRMAC 2009, 2010 Pre-Millstone test data into RASCAL4.0: "Field Monitoring to Dose" • Co-58 4.75 E2 pCi/100cm2 • Co-60 5.00 E3 pCi/100cm2 • I-131 9.70 E6 pCi/100cm2 • I-133 5.50 E6 pCi/100cm2 • Cs-134 5.00 E4 pCi/100cm2 • Cs-137 2.01 E4 pCi/100cm2
• Found DRL results (1st year, 2nd year, 50 year - mR/h - using mix): • • RASCAL 4.0 (11.1, 0.0986, 11.2) • TurboFRMAC 2009 (11.2, 0.0986, 11.2) • TurboFRMAC 2010 (11.1, 10.8, 11.2)
• TF 2010 – in order to plot, calculates 2nd yr DRL at beginning of 1st yr
RASCAL / NARAC
• NRC exports a source term to NARAC (IMAAC) • NARAC uses that source term as input to its
3D model and then posts results back for NRC to use and quality control (QC).
• Comparisons have been done at several exercises.
• During Japan incident, good NRC-DOE alliance, and due to complexities, DOE NIT QCed.
Results from Millstone Exercise Distance To Which Dose Was Exceeded
RASCAL NARAC
TEDE > 1 rem 1.8 km 7.7 km
> 5 rem 0.7 km 3.1 km
Thyroid > 5 rem 13 km 11.9 km
> 25 rem 2.2 km 4.5 km
RASCAL lower, 4x for TEDE, 1-2x for thyroid. Expected with the new transport and diffusion models.
Automated Meteorological Data Retrieval
• Prototype being developed by PNNL • Will access National Weather Service data via
the internet • Observations reported hourly but retained for
only 1 hour • Forecast updated every 3 hours; gridded • NARAC supported NRC with Met for Daiichi
Issues to be Addressed
• How to keep the data available to RASCAL current? – Regular, scheduled retrieval; full U.S. or just sites? – Run on demand
• How to get site tower data in? – Manual entry – Interface with ERDS
• Support for events that happened in the past • Support for “canned” meteorology
New source term work
• SOARCA – Have a LTSBO scenario from Sandia – Need others to be developed – Will greatly change the timing for source terms
• New reactor designs • Standardization of source term files
– Would XML be a useful format? – Improve ease of export and import
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
0 5 10 15 20 25
Core
frac
tiona
l rel
ease
to co
ntai
nmen
t
Time (hrs) since reactor shutdown
PWR Melcor source term - noble gas
PWR Nureg-1465 source term - noble gas
PWR Melcor source term - halogen
PWR Nureg-1465 source term - halogen
PWR Melcor source term - alkali metals
PWR Nureg-1465 source term - alkali metalsGap release
Early in-vessel
Ex-vessel
Late in-vessel
SOARCA – NUREG-1465 vs Melcor
Distribution Issues
• Have been able to freely distribute RASCAL in the U.S. and fairly easily worldwide
• May be restrictions coming • Requirements
– Non-Disclosure Agreement – More stringent registration of users – Protected distribution
Work with other Groups
• Unified RASCAL Interface (URI)- continue to support the Entergy / Exelon effort
• InterRAS – provide support for the IAEA international version of RASCAL
• Improve ways to stay in touch with RASCAL users
User Forum Ideas
• Online forum for sharing questions and answers between users
• Online resource for solving problems with the software
• Gathering place for new ideas, requests for changes and new capabilities
• Send your thoughts and ideas to George Athey and Lou Brandon
ISSUES – Still Being Resolved
• Large variation in results from past models • Can’t easily calculate new dispersion
parameters from 1st principles. • Which model is better for protective action
decisions? • How would one go about upgrading old
models? In RASCAL 4, the activity released remains about the same while the distribution
curve flattens.