ML112220605
| ML112220605 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 12/17/2003 |
| From: | FirstEnergy Nuclear Operating Co |
| To: | NRC/RGN-III |
| References | |
| EA-03-197 | |
| Download: ML112220605 (27) | |
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Desired Outcome
- Ensure a consistent understanding of the issue
- Present the causes and corrective actions
- Discuss further actions
- Present results from updated safety assessment
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Background
- Emergency Service Water (ESW) Pump "A" coupling failed
- Enforcement discretion requested and granted (no net increase in risk)
- Repairs completed well within the discretionary period
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Root Cause Evaluated
- Evaluated the environment/application
- Conducted a detailed laboratory analysis
- Performed a detailed stress analysis
- Fracture mechanics were evaluated
Root Cause Conclusion
- Stress corrosion cracking is the root cause Improper installation due to inadequate procedure Susceptible material Environment considered in design/operation
- Corrective actions address both installation and material
Extent of Condition Examined
- Safety and non-safety related pumps were included
- Similarities in configuration, couplings, and maintenance instructions were examined ESW Pump "8" - found to be identical ESW Pump "e" - similar
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Corrective Actions ESWPumps
- Pump operability has been assured
- Further actions will be taken to assure continued reliability ESW Pump "A" rebuild in 2004 ESW Pump "8" inspect in 2004, rebuild in 2007 ESW Pump "e" rebuild in 2004
Corrective Actions Procedures and Material
- Revision of procedures for ESW pumps
- Material upgrades for all ESW pumps New requirements for heat treatment, hardness, and documentation 100
Collective Significance Review Process
- Systematic evaluation of a collection of documented events or conditions
- Multidiscipline Review Team formed November 3, 200;3
- Scope includes four mitigating system equipment failures over last year
Collective Significance Review - Matrix Matrix used - Categories/Facts
- Problem category examples:
Procedure guidance Training Material deficiencies Design deficiencies
- Problem fact examples:
Event type Organization Cause code FENOC
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Collective Significance Review - Results Areas for Improvement Two collective issues identified during common cause evaluation
- Electrical/Mechanical maintenance instruction deficiencies
- Procedure "use" categories not pre-determined
Content of Procedures
==
Conclusion:==
- Procedures were root or contributing causes Actions:
- 75 maintenance instructions will be systematically assessed
- Results of assessment will determine need for comprehensive procedure upgrade
- Interim - Safety related procedures will be reviewed as part of the work planning
Use of Procedures
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Conclusion:==
- Procedure use categories not assigned Actions:
- Interim - maintenance instructions will be "In Field Reference"
- "Use" category will be identified in maintenance instructions
Collective Significance Review - Summary Common causes are understood Comprehensive actions are being taken Systematic assessment will be used to adjust scope and timeliness
Summary - Cause and Corrective Actions Root and contributing causes are understood Corrective actions are comprehensive Extent of condition and extent of cause are being addressed
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Initial Safety Assessment Initial characterization of incremental core damage and large early release probabilities (ICCDP and ICLERP)
- ICCDP (including internal events) = 2.03E-6
- ICCDP (seismic, fire, and external flooding) = negligible
- ICLERP = 1.S6E-7
Safety Assessment Basis. for Initial Assesstnent
- Level 1 PSA model used Includes all failure modes Simplified assumptions due to model and computer capabilities (no time dependence between event failures)
No consideration given to the time dimension relative to the ESW Pump "A" coupling failure Basis for Updated Assessl71ent
- The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time was partitioned
- Only the applicable scenarios based on this event were considered
- Human Reliability Analysis (HRA) was performed
Results of Updated Safety Assessment Updated characterization of incremental core damage and large early release probabilities (ICCDP and ICLERP)
- ICCDP (including internal events) =8.5E-7
- ICCDP (seismic, fire, and external flooding) = 1.2E-7 I:
- ICLERP = <1.0E-7 (qualitatively)
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Conclusion:==
- ICCDP (including external events) = 9.7E-7
- ICLERP <1.0E-7 (qualitatively)
Low safety significance using a more detailed and accurate evaluation method
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