ML20151J045
| ML20151J045 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 06/07/1984 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| Shared Package | |
| ML20151J049 | List: |
| References | |
| NUDOCS 8406190607 | |
| Download: ML20151J045 (5) | |
Text
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JUN 7 1984 Docket No. 50-352/353 Mr. V. 5. Boyer, Sr. Vice-President Nuclear Power Philadelphia Electric Company 2301 Market Street Philadelphia, Pennsylvania 19101
Dear Mr. Boyer:
SUBJECT:
REVIEW 0F THE LIMERICK RISK ASSESSMENTS Members of the staff met with Philadelphia Electric Company representatives on March 30, 1984 to describe areas where our review of your risk assessments of the Limerick Generating Station has identified potential improvements.
This letter is to affirm our comments during that meeting.
Over the past few years, our staff and consultants have met frequently to exchange information concerning the plant and the assessments of its risk in a high population density area.
The attitude exhibited by Philadelphia Electric Company during these exchanges has been valuable to the conduct of our. review.
The public risks from the Limerick Generating Station have been reduced through design changes motivated by what the Philadelphia Electric Company learned during the performance of the Probabilistic Risk Assessments.
During the staff's review, we identified certain other potertial improvements which were described at the meeting of March 30, 1984 The Philadelphia Electric Compa'ny indicated an interest in these potential improvements and subsequently provided comments (Letter to A. Schwencer, NRC, from J. S. Kemper, PECo, subject: Limerick Generating Station, Units 1 and 2 Risk Assessments,
, dated April 11, 1984).
The Philadelphia Electric Company indicated that it was aware of the three specific improvements and had taken steps already tc accelerate the scheduled ADS modifications, to mitigate HPCI and RCIC room heatup, and to train operators in the extended use of the containment sprays.
1 We all know that there are large uncertainties associated with the numerical results from current risk assessments.
However, we believe that the 3
potential improvements identified from the perfcemance of the risk assessments transcend those uncertainties.
Additto.Pily, the process of conducting risk assessments provides a means of integrating the myriad of 6*
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C potential hazard considerations into a perspective that enables us to better discriminate what is of central importance to reactor safety from what is not of central importance.
Such a tool provides a perspective that enhances communications among design and operational groups with different responsibilities.,
I or areas of expertise as well.
I want to take this opportunity to reemphasize our interest in your maintaining and continuing to utilize the risk assessments j
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during startup and operations.
Some elements of this activity are described in We look forward to hearing your response to this preview of the results of l
our review in time to reflect any comments when documenting our review.
Sincerely,
..as a.
a 4 R L aunal,4 Harold R. Denton, Director Office of Nuclear Rametne Don.1=+4a.
Attachments:
- 1. Elements of Continued Use of Ris Assessments.
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Key Elements of Continued Use of Risk Assessments 1.
Formal calculations of quantitative measures of importance to risk for initiating events, systems, components, human interactions in maintenance, surveillance, and operations.
Such figures of merit bearing upon the importance of safety can be illuminating in several ways:
a) they may reveal limitations in the PRAs; b) they are useful in the training of operators and maintenance personnef; and c) they are useful in the evaluation of procedures,' technical specifications, and situations that may arise in plant operations.
2.
Fault Ha:ards Analysis applied to hypothetical errors in the conduct of
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maintenance procedures, surveillance procedures, normal and emergency operating procedures, and technical specifications.
This constitutes a formal "what if" examination of potential human error in the conduct of operations.
3.
Where the importance-to-risk and the fault hazards analysis suggest that procedures may warrant improvement, the analysis can be extended to human error Failure Mode Effects Analysis.
Changes, in procedures, f,
technical specifications, operator training, system design, and/or l
control room simulator design as appropriate, suggested by such analyses, can be considered and where plausibly cost effective, be instituted.
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4.
Operations and maintenance personnel can be trained on the results of the studies into the importance-to-risk of their responsibilities, taught pattern recognition for the more vulnerable plant configurations, or circumstances and diagnosis of the more important accident scenarios.
5.
From time to time the PRA quantification can be updated to reflect accumulated experience on the frequency of component failures, human errors, and initiating events.
This effort can te made ecer.cmical by employing the quantitative measures of importance-to-risk to assess the significance of altered f ault event frequency, so tnat comprehensive and burdensome recalculations of risk are rarely necessary.
6.
Philadelphia Electric, can devise and implement criteria spelling out
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thresholds for corrective action upon discoveries of less-than-expected 4
system reliability, procedural adequacy, or greater-than-expected risk, where the Limerick PRAs serve as the frame of reference.
7.
The risk assessment models can assess the risk importance to Limerick of precursor events that occur at other plants.
Criteria can be established to determine the relevance of the events at other plants to Limerick in the sense of NUREG/CR-2497.
8.
The results of the importance-to-risk evaluations can be made widely available, including the utility's quality assurance organization not only to enable reviews to be made, but for use in sharpening the focus or allocation of emphasis in the work of the QA audits.
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9.
The risk assessments and the assessments of icportance-to-risk based 1
upon it, can be mai,ntained, and when appropriate, revised to make it a current, up-to-date evaluation tool.
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