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Recent Developments Regarding NRC Guidance on Control Room Habitability Assessment R. Brad Harvey, CCM Marlboro, MA

Recent Developments Regarding NRC Guidance on Control Room Habitability Assessment R. Brad Harvey, CCM Marlboro, MA. Control Room Habitability Assessment. Outline Background Radiological Assessments Hazardous Chemical Assessments Conclusion. Control Room Habitability Assessment.

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Recent Developments Regarding NRC Guidance on Control Room Habitability Assessment R. Brad Harvey, CCM Marlboro, MA

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  1. Recent Developments Regarding NRC Guidance on Control Room Habitability Assessment R. Brad Harvey, CCM Marlboro, MA

  2. Control Room Habitability Assessment Outline • Background • Radiological Assessments • Hazardous Chemical Assessments • Conclusion

  3. Control Room Habitability Assessment Background • Control Room Habitability Requirements • Appendix A to 10 CFR Part 50, GDC 19 • A control room is to be provided from which actions can be taken to maintain the reactor in a safe condition under accident conditions • Adequate protection is to be provided to permit occupancy under accident conditions without personnel receiving excessive radiation exposure

  4. Control Room Habitability Assessment Background • NRC Concerns • CR Habitability Knowledge • Affect of ventilation system changes and realignments • CR Boundary Maintenance • Degradation of seals, fans, ductwork, etc • CR Boundary In-leakage Testing • Measured values exceeded assumed values

  5. Control Room Habitability Assessment Background • Industry Response • NEI 99-03 CR Habitability Guidance Document • Areas of NRC/Industry Disagreement • Acceptable types of baseline in-leakage tests • Frequency of in-leakage tests • Tech Spec surveillance requirement versus CR Habitability Control Program • NRC Response • Generic Letter • Regulatory Guides

  6. Control Room Habitability Assessment Background • Regulatory Guides • DG-1114, CR Habitability, March 2002 • DG-1113, Radiological Consequences of DBA (Traditional Source Term), March 2002 • RG 1.183, Radiological Consequences of DBA (Alternative Source Term), July 2000 • DG-1111, Atmospheric Dispersion for Radiological Assessments, December 2001 • RG 1.78 Rev 1, Atmospheric Dispersion for Hazardous Chemical Assessments, December 2001 • DG-1115, Demonstrating CR Envelope Integrity, March 2002

  7. Control Room Habitability Assessment Radiological - Previous Method • Murphy-Campe (ground level release only) • Point Release • Area Source Release

  8. Control Room Habitability Assessment Radiological - Previous Method • Murphy-Campe (with site data)

  9. Control Room Habitability Assessment Radiological - Previous Method • Murphy-Campe (without site data)

  10. Radiological - Previous Method Murphy-Campe (wind direction window) Control Room Habitability Assessment

  11. Radiological - Previous Method Murphy-Campe Limitations Too conservative? No elevated (stack) releases No plume rise Control Room Habitability Assessment

  12. Radiological - Revised Method ARCON96 (ground level release) Control Room Habitability Assessment

  13. Radiological - Revised Method ARCON96 (ground level release) Low wind speed corrections Control Room Habitability Assessment

  14. Radiological - Revised Method ARCON96 (ground level release) Building wake corrections Control Room Habitability Assessment

  15. Radiological - Revised Method ARCON96 (ground level release) Area Source Control Room Habitability Assessment

  16. Radiological - Revised Method ARCON96 (elevated release) Control Room Habitability Assessment

  17. Radiological - Revised Method ARCON96 (elevated release - flow reversal) Control Room Habitability Assessment

  18. Radiological - Revised Method ARCON96 (plume rise) Stacks Vents Control Room Habitability Assessment

  19. Radiological - Revised Method ARCON96 (plume rise) Vents High Energy Releases (steam relief valves) Stack Exit Velocity >5 times 95%wind speed Control Room Habitability Assessment

  20. Radiological - Revised Method ARCON96 (time averaging) ARCON96 (wind direction window) 90º Control Room Habitability Assessment

  21. Radiological - Method Comparison Control Room Habitability Assessment F Stability x = 30 m A = 2000 m^2

  22. Radiological - Method Comparison Control Room Habitability Assessment F Stability x = 30 m A = 2000 m^2

  23. Hazardous Chemical - Previous Method RG 1.78 Rev. 0 Max Concentration Accident (puff release) Appendix B to RG 1.78 Rev 0; NUREG-0570 Max Concentration Duration Accident (continuous release) RG 1.3/1.4 Control Room Habitability Assessment

  24. Hazardous Chemical - Revised Method RG 1.78, Rev. 1 Max Concentration Accident (puff release) HABIT/EXTRAN (single puff release) Max Concentration Duration Accident (cont’ release) HABIT/EXTRAN (multiple puff releases) Control Room Habitability Assessment

  25. Conclusion There is consistency between the revised radiological (ARCON96) and hazardous chemical (EXTRAN) atmospheric dispersion models Multiple runs required for EXTRAN Both models use revised plume dispersion coefficients Low wind speed correction Building wake correction Plume rise considerations are allowed for high energy (steam line) radiological releases Control Room Habitability Assessment

  26. Recent Developments Regarding NRC Guidance on Control Room Habitability Assessment R. Brad Harvey, CCM Marlboro, MA

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