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

• Outline
• Background
• Radiological Assessments
• Hazardous Chemical Assessments
• Conclusion

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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

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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

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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

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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

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Control Room Habitability Assessment

• Radiological - Previous Method
• Murphy-Campe (ground level release only)
• Point Release
• Area Source Release

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Control Room Habitability Assessment

• Radiological - Previous Method
• Murphy-Campe (with site data)

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Control Room Habitability Assessment

• Radiological - Previous Method
• Murphy-Campe (without site data)

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Control Room Habitability Assessment

• Radiological - Previous Method
• Murphy-Campe (wind direction window)

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Control Room Habitability Assessment

• Radiological - Previous Method
• Murphy-Campe Limitations
• Too conservative?
• No elevated (stack) releases
• No plume rise

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (ground level release)

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (ground level release)
• Low wind speed corrections

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (ground level release)
• Building wake corrections

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (ground level release)
• Area Source

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (elevated release)

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (elevated release - flow reversal)

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (plume rise)
• Stacks
• Vents

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (plume rise)
• Vents
• High Energy Releases (steam relief valves)
• Stack Exit Velocity gt5 times 95wind speed

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Control Room Habitability Assessment

• Radiological - Revised Method
• ARCON96 (time averaging)
• ARCON96 (wind direction window)
• 90º

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Control Room Habitability Assessment

• Radiological - Method Comparison

F Stability x 30 m A 2000 m2
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Control Room Habitability Assessment

• Radiological - Method Comparison

F Stability x 30 m A 2000 m2
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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

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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)

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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

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