1. RETS REMP Conference 6/24-26/2002 Estimates of ISFSI Site Boundary Doses Andrew Hodgdon, Jo Ann Pelczar Radiological Engineering Group and Mel Gmyrek Environmental Laboratory FRAMATOME ANP DE&S 400 Donald Lynch Boulevard Marlborough, MA 01752 Telephone: (978) 568-2522 e-mail: Melvin.Gmyrek@Framatome-ANP.com

2. RETS REMP Conference 6/24-26/2002 ISFSI = I ndependent S pent F uel S torage I nstallation Wet Pool Dry Pad

3. RETS REMP Conference 6/24-26/2002 Feds Regulate to 25 mrem/year to Real Member of Public There are: Plants without ISFSIs Plants with ISFSIs Decommissioned Plants with ISFSIs Regulations: (plant) 40CFR190 “provide reasonable assurance that annual dose does not exceed 25 millirems” (ISFSI) 10CFR72.104 “annual dose to real individual beyond controlled area must not exceed 25 mrem”

4. RETS REMP Conference 6/24-26/2002 Factors Affecting Compliance 1.State limit is lower than Fed’s (2 plants) 2.Small Site (< 3000 feet to boundary) 3.Public access to the site (roads, camp) 4.Nearby dwellings (homes and condominiums) 5.Nearby schools 6.Nearby commercial properties

5. RETS REMP Conference 6/24-26/2002 Plant Modifications That Increase Dose Add ISFSI 20 mrem/h contact (typical) Dose is higher at vents Hydrogen Water Chemistry BWR only 100 mR/hr turbine area Store Old Steam Generators 1 mR/h contact Sell-off property Up-rate power Store waste (old turbine blades)

6. RETS REMP Conference 6/24-26/2002 Options to Demonstrate Compliance 1.Take credit for Occupancy 2.Predict with Models 3.Make Measurements 4.Model and Measure (M&M) 5.Buy Property 6.Build Shield or Berm 7.Limit ISFSI Loads less fuel lower burnup longer decay time

7. RETS REMP Conference 6/24-26/2002 1.Take Credit for Occupancy Start with conservative calculation(s) Residents (100%) School, roads, visitors center, hikers, clam diggers, etc. (<100%) Administrative requirements to update basis yearly Options to Demonstrate Compliance (cont’d)

8. RETS REMP Conference 6/24-26/2002 2.Predict With Models (Without Measurements) Highly uncertain and/or very expensive MicroSkyshine Simple Greater than 100% errors MCNP - very detailed, more accurate but expensive Options to Demonstrate Compliance (cont’d)

9. RETS REMP Conference 6/24-26/2002

10. 3.Make Measurements (Without Models) Background variation (noise) swamps dose rate (signal) Detection Limit is 70 mrem/year* Distance curve is required (* The detection limit for “on/off” sources, like BWR N-16, is 10 mrem/year) Options to Demonstrate Compliance (cont’d)

11. RETS REMP Conference 6/24-26/2002 Background Variation

12. RETS REMP Conference 6/24-26/2002 Distance Curves Highly problem dependent Add significant error Are very hard to measure Can be measured for rare “on/off” sources Turning the source on and off allows the background to be measured at the same location and at nearly the same time. Unfortunately, an ISFSI is always on. Here are the four Distance Curves we know about

13. RETS REMP Conference 6/24-26/2002 Distance Curves for “On/Off” Sources

14. RETS REMP Conference 6/24-26/2002 4.Model and Measure (M&M) Pro More accurate Model (MCNP) provides distance curve Surveys validate the results Model suitable for further engineering Con Need experts in modeling and measurements Options to Demonstrate Compliance (cont’d)

15. RETS REMP Conference 6/24-26/2002 Recipe for M & M (Model and Measure) 1.Set up model (MCNP) contact model distance model 2.Take contact surveys to calibrate model 3.Take near surveys to validate distance curve 4.Run model at boundary to get answer

16. RETS REMP Conference 6/24-26/2002 Contact versus Distance Model Contact Model Details inside the building or bunker Complex 10 to 20 hours to run Results in contact dose rates Distance Model Starts where contact model leaves off Simple Runs in 10 minutes Results in site boundary dose rates

17. RETS REMP Conference 6/24-26/2002 Three Examples Ex. #1 BWR N-16 Streaming (presented at ANS RPSD 98) Ex. #2 NUHOMS ISFSI (presented at ANS RPSD 02) Ex. #3 NAC ISFSI (in process)

18. RETS REMP Conference 6/24-26/2002 Ex. #1 - BWR N-16 Streaming

19. RETS REMP Conference 6/24-26/2002 Assignment Shorten outage by a half day by removing some N-16 shielding while at power. Risk - violate boundary limit. Solution - use M&M to: Guide shield removal Validate boundary dose at end of year

20. RETS REMP Conference 6/24-26/2002 Dose Points

21. RETS REMP Conference 6/24-26/2002 Turbine Building Section

22. RETS REMP Conference 6/24-26/2002 Plan

23. RETS REMP Conference 6/24-26/2002 Contact vs Distance Model

24. RETS REMP Conference 6/24-26/2002 Calibrated Distance Curve

25. RETS REMP Conference 6/24-26/2002 Zoom at Fenceline

26. RETS REMP Conference 6/24-26/2002 Ex. #2 - NUHOMS ISFSI (20 bunkers shown)

27. RETS REMP Conference 6/24-26/2002 Assignment Build contact dose rate model to: Permit further engineering (more fuel in bunker) Permit site boundary calculations

28. RETS REMP Conference 6/24-26/2002 Facility Description 900 PWR Assemblies in 36 bunkers 10 metric tons fuel per bunker 16 kW heat 4E16 photons/second/bunker (measured value) 4E9 neutrons/second/bunker (measured value) Major Nuclides - Cs-137, Co-60, and Cm-244

29. RETS REMP Conference 6/24-26/2002 Canister For 24 Assemblies

30. RETS REMP Conference 6/24-26/2002 Canister Being Pushed Into Bunker

31. RETS REMP Conference 6/24-26/2002 1.Built MCNP Model 2.Used Contact Surveys to Calibrate Model neutrons <1 mrem/h (not reported here) photons 20 to 100 mR/h 3.Distance Model Not Yet Completed Results

32. RETS REMP Conference 6/24-26/2002 Model / Measured

33. RETS REMP Conference 6/24-26/2002 Ex. #3 - NAC Type ISFSI

34. RETS REMP Conference 6/24-26/2002 Assignment Demonstrate compliance Reduce control area

35. RETS REMP Conference 6/24-26/2002 Concrete Bunkers

36. RETS REMP Conference 6/24-26/2002 Contact Model

37. RETS REMP Conference 6/24-26/2002 Model Predictions Contact Model Runs take 8 hours 20 mrem/h contact Neutrons at vents and top Distance Model Runs take 10 minutes 25 mrem/year at about 740 feet Neutron dose less than 4% Model provides spectrums

38. RETS REMP Conference 6/24-26/2002

39. Measuring Background (Reuter-Stokes HPIC - ISFSI Empty)

40. RETS REMP Conference 6/24-26/2002 Measurements In Progress

41. RETS REMP Conference 6/24-26/2002 As a Results of Using M & M (Modeling and Measurement) Ex. #1 – Saved a half day during the refuel outage Ex. #2 - Built a validated model will be used to analyze higher loading will be used for site boundary doses Ex. #3 - Work in progress to reduce Control Area

42. RETS REMP Conference 6/24-26/2002 “Must Not Exceed 25 mrem per year” Measurement alone can’t demonstrate compliance Models alone can’t demonstrate compliance What works is modeling and measurement combined

43. RETS REMP Conference 6/24-26/2002 Andrew Hodgdon (Radiological Engineering Group) (978) 568-2750 Andrew.Hodgdon@Framatome-ANP.com Framatome ANP DE&S 400 Donald Lynch Boulevard Marlborough, MA 01752 CONTACTS Mel Gmyrek (Environmental Laboratory) (978) 568-2522 Melvin.Gmyrek@Framatome-ANP.com Framatome ANP DE&S Environmental Laboratory 29 Research Drive Westborough, MA 01581-3913