DOSE ASSESSMENT. URI vs Rascal 4.2 vs Gaussian vs Midas

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Marvin Nichols
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1 DOSE ASSESSMENT URI vs Rascal 4.2 vs Gaussian vs Midas

2 THE PLAYERS Unified RASCAL Interface RASCAL 4.2 Simple Gaussian Model Midas

3 THE DISCLAIMER There are many assumptions made in dose projections and the estimated range of uncertainty between projected and actual off-site doses for severe accidents is best within a factor of 10, and at worst, off by a factor of 100,000. Sources: Nuclear Regulatory Commission Regulation NUREG-1210 FEMA IS 303

4 THE ASSUMPTION One of my NPPs finally started using Unified RASCAL Interface (URI) for their dose assessment (after much hype) I know from various meetings, trainings and conversations that URI uses the RASCAL engine But which one? Theoretically if you get the right one they should match exactly. I ve got RASCAL 3.0.5, 4.1, 4.2 I think we re up to now

5 THE DISCOVERY RASCAL 4.2 URI/RASCAL Interface Description: (RSCS Unified RASCAL Interface URI Ensuring Accuracy and Ease of RASCAL Use for Dose Assessment Professionals, April 2012) This interface provides a specific overlay on the existing RASCAL 4.2 meteorological, dispersion, and dose assessment models Leads to Expectation: URI and RASCAL 4.2 should match closely

6 THE TEST Source Term: Clad TAS: 1:00 Release Duration: 4:00 NG: 1.00E+02 Ci/s Iodines: 7.45E+01 Ci/s Particulate: 3.87 Ci/s Wind Dir: 0 degrees Wind Speed: 5 mph Stability Class C Precipitation: None

7 A CLOSER LOOK We ve exceeded PAGs out to 6.5 mi. It s likely you ll be receiving a PAR from the plant to evacuate a 5 mi radius and 10 mi downwind. Do you agree?

8 THE T YPICAL METHOD Typical Dose Assessor using RASCAL Effluent Releases by Mixtures

9 THE T YPICAL METHOD Why? Because that s what I got on my plant message form I got the release rates in Ci/s from the plant dose assessor at the EOF I m ahead of the game, I back-calculated the source term release rate (Ci/s) from field team data Where do you get your data?

10 THE T YPICAL METHOD Putting in my stuff:

11 THE T YPICAL METHOD Ensuring matching components:

12 THE T YPICAL METHOD Same MET data:

13 THE RESULT URI RASCAL 4.2 TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 59 rem 1600 rem 2 mile 1.44 rem 23.8 rem 4.7 rem 130 rem 5 mile rem 5.77 rem 0.95 rem 28 rem 10 mile rem 3.83 rem 0.56 rem 17 rem

14 LET S SHADE THAT! URI RASCAL 4.2 TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 59 rem 1600 rem 2 mile 1.44 rem 23.8 rem 4.7 rem 130 rem 5 mile rem 5.77 rem 0.95 rem 28 rem 10 mile rem 3.83 rem 0.56 rem 17 rem

15 HOW FAR DOES IT GO? URI RASCAL 4.2 TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 59 rem 1600 rem 2 mile 1.44 rem 23.8 rem 4.7 rem 130 rem 5 mile rem 5.77 rem 0.95 rem 28 rem 10 mile rem 3.83 rem 0.56 rem 17 rem 15 mile 13 rem 20 mile 9.8 rem 30 mile 3.7 rem Somewhere in the 25 mi range. What now? Ad-hoc PARs?

16 WAIT, I HAVE A BACKUP METHOD! To the Gaussian!! Most dose assessors have an alternate method available, either a homemade dose modelling program or worksheet (aka napkin math )

17 WAIT, I HAVE A BACKUP METHOD! URI Gaussian TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 327 rem 1,085 rem 2 mile 1.44 rem 23.8 rem 24.6 rem 813 rem 5 mile rem 5.77 rem 4.21 rem 138 rem 10 mile rem 3.83 rem 1.08 rem 35.5 rem Yikes! (I m not even going to look how far that goes out) I think we exceeded the factor of 10 comparison

18 SO WHAT WENT WRONG? Since URI uses RASCAL 4.2 dispersion and dose engine, if everything is equal in the inputs, the results should be nearly identical. Suggestions?

19 THE SOLUTION Using Effluent Releases - by Mixtures is wrong Use Effluent Release Rates by Nuclide

20 SURE, NO PROBLEM! Let me just get that data Good thing this is a Clad accident (has the fewest isotopes)

21 INPUTTING, INPUTTING, INPUTTING

22 AND THE WINNER IS? URI RASCAL 4.2 TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 20 rem 330 rem 2 mile 1.44 rem 23.8 rem 1.60 rem 26.0 rem 5 mile rem 5.77 rem rem 5.60 rem 10 mile rem 3.83 rem rem 3.50 rem

23 CLOSER, BUT NOT QUITE THERE YET One more thing to consider RASCAL defaults to a 10m Release height Many dose assessors either skip by this or mistakenly think it s the stack height The actual stack height for this plant is 58m Changing the Release height to 58m results in Note: RASCAL displays results in two significant figures

24 THERE IT IS URI RASCAL 4.2 TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 18.2 rem 297 rem 18 rem 300 rem 2 mile 1.44 rem 23.8 rem 1.4 rem 24 rem 5 mile rem 5.77 rem 0.32 rem 5.8 rem 10 mile rem 3.83 rem 0.19 rem 3.8 rem

25 NEXT STEPS How does this work with other dose models (Midas, Rad Dose 5, older RASCAL versions, newer RASCAL versions, etc?) Can you easily obtain the data necessary to perfor m dose calculations this way?

26 MIDAS Situation inputs for MIDAS: TAS: 1 hour Containment Bypass Release Gap Release Normal Filtration Wind: From 270 deg Wind Speed: 5 mph Duration: 4 hour NG: 1.0e+02 Ci/s I-131 Equiv.: 7.2e-02 Ci/s Particulate: 7.3e-03 Ci/s Individual Isotope Release Rate Available µci/s

27 MIDAS VS GAUSSIAN MIDAS Gaussian Effluent Release Rates Method TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 0.75 rem 3.2 rem rem rem 2 mile 0.23 rem 0.73 rem rem rem 5 mile rem 0.13 rem rem rem 10 mile rem rem rem rem

28 MIDAS VS RASCAL 4.2 MIDAS RASCAL 4.2 Effluent Releases - Mixtures TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 0.75 rem 3.2 rem 0.28 rem 1.6 rem 2 mile 0.23 rem 0.73 rem rem 0.13 rem 5 mile rem 0.13 rem rem rem 10 mile rem rem rem rem

29 MIDAS VS RASCAL 4.2 MIDAS RASCAL 4.2 Effluent Releases - Nuclide TEDE CDE Thyroid TEDE CDE Thyroid SB (0.5 mi) 0.75 rem 3.2 rem 0.42 rem 1.6 rem 2 mile 0.23 rem 0.73 rem rem 0.12 rem 5 mile rem 0.13 rem rem rem 10 mile rem rem rem rem

30 QUESTIONS?

31 VERSION CONTROL Document owner: Greg Gothard Contact: Created: 12/22/2015 Last Revision: Revision Number: 0

GOOD SCIENCE Vs UNCERTAIN REGULATORY GUIDANCE or HOW CHI/Q AFFECTS NUCLEAR SAFETY

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