1. Recent Developments Regarding Control Room Habitability Assessment
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 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. Control Room Habitability Assessment
Radiological - Previous Method
Murphy-Campe (wind direction window)

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

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

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

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

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

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

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

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

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

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

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

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

23. Control Room Habitability Assessment
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

24. Control Room Habitability Assessment
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)

25. Control Room Habitability Assessment
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

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