1. Environmental Neutron TLD Monitoring for ISFSI Matthew J. Scannell, NextEra Energy Seabrook James Giard - AREVA NP Inc. Environmental Laboratory Jeffrey Raimondi, AREVA NP Inc. Environmental Laboratory RETS/REMP Workshop June 2009

2. 2 Seabrook Station ISFSI Operational in 3 rd Quarter, 2008 –ISFSI located amongst occupied buildings (workers and members of the public) –Gamma dose expected to be main component –Desire minor neutron dose to be quantified AREVA-NP Environmental Laboratory TLD Service –Routine gamma environmental TLD measurements –Neutron measurement capabilities with 808/814 badge Environmental Neutron TLD Monitoring for ISFSI Introduction

3. 3 Seabrook Station ISFSI Layout –ISFSI Facility design –Surrounding Buildings AREVA-NP 808/14 Badge –Design features –Determination of Neutron Correction Factor –Determination of MDD neutron as a function of gamma dose –Expected Neutron Sensitivity Seabrook Station ISFSI Monitoring Results –3 rd Quarter, 2008, during first spent fuel load campaign –4 th Quarter, 2008, after spent fuel loaded Summarize 808/814 Badge Capabilities for ISFSI Neutron Monitoring Environmental Neutron TLD Monitoring for ISFSI Presentation Summary

4. 4 Environmental Neutron TLD Monitoring for ISFSI Seabrook ISFSI View Looking West

5. 5 Environmental Neutron TLD Monitoring for ISFSI Seabrook ISFSI View Looking North

6. 6 Environmental Neutron TLD Monitoring for ISFSI Seabrook ISFSI View Looking South

7. 7 Environmental Neutron TLD Monitoring for ISFSI Seabrook ISFSI View Looking East

8. 8 Environmental Neutron TLD Monitoring for ISFSI Seabrook ISFSI NUHOMS® Horizontal Storage Modules with Shield Blocks at Lower Vents

9. 9 808/814 Badge Lithium Borate Elements –Three 814 elements (η+γ), natural isotopic abundances –Three 808 elements (γ-only), depleted of 6 Li and 10 B –Neutron signal subtract average 808 from average 814 Environmental Neutron TLD Monitoring for ISFSI AREVA-NP 808/814 Badge

10. 10 AREVA-NP 808/814 Badge (Continued) 808/814 Badge Environmental Holder Configuration –808/814 badge cases –Cases sealed in plastic pouches –Otterbox® water-proof holder Environmental Neutron TLD Monitoring for ISFSI

11. 11 808/814 Badge Neutron Correction Factor (NCF) –Overnight Irradiate 808/814 Badges at HSM lower vents –Neutron dose based on REM-500 tissue equivalent proportional counter (TEPC) ξ –Gamma dose based on 451B ion chamber –Total Dose (η+γ) is 162mrem –Neutron dose is 9.7 mrem (6% of total dose) –Result: NCF = 10.5 + 1.2 mR* n /mrem ξ REMBALL neutron meter (BF 3 tube in 9” Cd loaded polyethylene sphere) would have given similar NCF, within 15% Environmental Neutron TLD Monitoring for ISFSI Neutron Correction Factor

12. 12 808/814 Badge Natural Background Measurements Prior to ISFSI Operations –Ninety-seven Field Data Points: Quarterly measurements at ISFSI Monitoring Locations (outside & within buildings) normally used to establish historical background –Five “Fade” Badge Points: Dosed to known gamma levels (i.e. 200 mrem) Placed in field for quarter normally used to evaluate TL signal fade Environmental Neutron TLD Monitoring for ISFSI Background Measurements

13. 13 808/814 Badge Neutron Sensitivity (MDD neutron ) –MDD neutron = 4.65 * σ n /NCF [Eq. 1] (Currie) σ n = uncertainty in neutron signal NCF 10.5 mR* n /mrem 808/814 Badge MDD neutron as Function of Gamma Dose –Propagate 814 and 808 element uncertainty curves to get σ n vs gamma dose curve. Combine with [Eq. 1] to get: –MDD neutron = 0.494 * (LiBO gamma ) 0.4331 [Eq. 2] Where LiBO gamma = average 808 element responses. Environmental Neutron TLD Monitoring for ISFSI Neutron Minimum Detectable Dose Calculation

14. 14 MDD Equation Comparison Compare MDD neutron [Eq. 1] points and [Eq. 2] Line for Field data Environmental Neutron TLD Monitoring for ISFSI

15. 15 MDD Equation Comparison (Continued) Compare MDD neutron [Eq. 1] points and [Eq. 2] Line on Field & Fade data Environmental Neutron TLD Monitoring for ISFSI

16. 16 MDD Sensitivity Expected Annual Neutron Sensitivity for Workers and Members of Public Environmental Neutron TLD Monitoring for ISFSI QuarterlyExpected365-Day2000-hour400-hour12-hour GammaQuarterlyPublic atWorkersPublic at SignalMDD neutron Site BoundaryOn SiteFitness CenterS&N Center (mR*)(mrem) 402.449.82.20.450.013

17. 17 MDD neutron as Function of Gamma Dose –MDD neutron = 0.494 * (LiBO gamma ) 0.4331 [Eq. 2] Based on 4.65 σ n /NCF Critical Level LC neutron as Function of Gamma Dose –LC neutron = 0.248 * (LiBO gamma ) 0.4331 [Eq. 3] Based on 2.33 σ n /NCF Environmental Neutron TLD Monitoring for ISFSI Analysis of ISFSI 808/814 Badge Neutron Results

18. 18 Seabrook ISFSI Gross Gamma and Neutron Results (mrem) Third Quarter, 2008 Outside Locations and Buildings Environmental Neutron TLD Monitoring for ISFSI

19. 19 Seabrook ISFSI Gross Gamma and Neutron Results (mrem) Fourth Quarter, 2008 Outside Locations and Buildings Environmental Neutron TLD Monitoring for ISFSI

20. 20 Seabrook ISFSI Gross Gamma and Neutron Results (mrem) Third Quarter, 2008 ISFSI PA Fence, Spent Fuel Loading Campaign Environmental Neutron TLD Monitoring for ISFSI

21. 21 Seabrook ISFSI Gross Gamma and Neutron Results (mrem) Fourth Quarter, 2008 ISFSI PA Fence, Shield Blocks at HSM Vents Environmental Neutron TLD Monitoring for ISFSI

22. 22 Seabrook ISFSI Monitoring Results Comparison of Neutron Contribution to Dose at ISFSI PA Fence –NCF determined at HSM vent is conservative once HSM vents are shielded. –Sky-shine neutrons are lower energy spectrum than at HSM vents –Sky-shine neutron-to-gamma ratio different than at HSM vents. Environmental Neutron TLD Monitoring for ISFSI Measurement Location Neutron Percentage of Total Dose Survey Instruments at HSM vent (From NCF Determination)6% Average of ISFSI Fence Locations Tl-75, 77, 78 and 79 Third Quarter 2008, During Spent Fuel Loading5% Average of ISFSI Fence Locations Tl-75, 77, 78 and 79 Fourth Quarter 2008, Shield Blocks at HSM Vents22%

23. 23 AREVA-NP 808/14 Badge for ISFSI Neutron Monitoring –Simple methods to determine NCF at suitable location with available survey meters –Good neutron sensitivity for monitoring worker and public doses –Curve established for MDD neutron as a function of gamma dose is applicable to each badge measurement. –NCF will, if anything, yield conservative neutron doses when the neutron spectrum shifts to lower energy When sky-shine predominates as distance from ISFSI increases Environmental Neutron TLD Monitoring for ISFSI Presentation Conclusions

24. 24 Seabrook Station ISFSI Monitoring Results –3 rd Quarter, 2008, Spent Fuel Loading Campaign No dose increases in surrounding buildings, or outside ISFSI ISFSI fence locations near HSM’s had gamma & neutron dose increase. (ISFSI fence was boundry of restricted area) –Neutron is 5% of total dose (neutron 6% at HSM vents) –4 th Quarter, 2008, HSM lower vents shielded by Jersey barriers No dose increases in surrounding buildings, or outside ISFSI. ISFSI fence locations near HSM’s had gamma & neutron dose increase. Much less than 3 rd quarter (due to shield blocks) –Neutron is 22% of total dose (neutron 5% for 3 rd Quarter) –Neutrons from sky-shine may be conservatively reported due to neutron energy spectrum being lower than at HSM vents. Environmental Neutron TLD Monitoring for ISFSI Presentation Conclusions (Continued)

25. 25 Environmental Neutron TLD Monitoring for ISFSI Questions ?