ML20046B753
| ML20046B753 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 07/29/1993 |
| From: | Storz L CENTERIOR ENERGY |
| To: | Gillespie F Office of Nuclear Reactor Regulation |
| References | |
| 2163, NUDOCS 9308060150 | |
| Download: ML20046B753 (3) | |
Text
C' CENTERIOR ENERGY Louis F. Sforz 300 Madison Avenue Vice President - Nuclear Toledo, OH 43652-0001 Davis-Besse (419)249-2300 Docket Number 50-346 License Number NPP-3 Serial Number 2163 July 29, 1993 Mr. Frank P. Gillespie, Director PMAS - Mail Stop 12-G18 United States Nuclear Regulatory Commission Vashington, D.C.
20555 Subj ect : Comments on Regulatory Review Group Report
Dear Mr. Gillespie:
The Toledo Edison Company, operator of the Davis-Besse Nuclear Power Station, has reviewed the Regulatory Review Group Report which was placed in the NRC Public Document Room on May 28, 1993, for a 30-day comment period (later extended to a 60-day comment period ending July 29, 1993 by 58 FR 33285). Toledo Edison strongly supports the NRC's and industry's efforts to identify and eliminate regulatory requirements and commitments that are economically burdensome yet provide little or no safety value. Toledo Edison concurs that the elimination of burdensome regulatory requirements could indirectly benefit safety, in that the freed up resources that vould result may be redirected to more safety-significant work.
As you are aware, the resources which Toledo Edison, or any utility, can make available to initiate burden reduction requests are limited.
Toledo Edison recognizes that the NRC's resources are clso limited. As our resources permit, Toledo Edison vill continue to initiate or participate in industry activities designed to reduce regulatory burden, provided the potential benefits outweigh the cost, and provided that there is a reasonable opportunity for NRC acceptance. The Reviev Group Report provides an excellent summary of potential opportunities in this area.
Specific comments on the report are included in the attachment to this letter.
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' I Page 2' If you have any questions regarding this matter, please contact Mr. Dale R. Vuokko, Manager - Regulatory Affairs'(Acting), at j
(419) 249-2366.
Sincerely,
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Attachment cc:
J. B. Ilopkins, NRC Senior Project Manager J. B. Martin, Regional Administrator, NRC Region III S. Stasek, DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board q
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Docket' Number 50-346 License Number NPF-3 Serial Number 2163 i
Attachment Page 1 Comments on the Regulatory Review Group Risk Technology Application,-Volume 4 Use the term "Probabilistic Safety Assessment" (PSA) vice the term Probabilistic Risk Assessment throughout the report.. While PSA techniques and applications are still relatively new, consistent i
terminology should be used within the industry and regulators. NUMARC, EPRI and utilities are using the term PSA; use of terminology with the word safety instead of risk may allow for a vider acceptance of these techniques.
In response to the first bullet on page 4-2 that discusses reliance on quantitative results from multiple plant-specific PSAs and the use of generic failure data, is one particular generic data base being i
proposed? Most PSA analysts have their own generic data base comprised f
of the generic sources available to them.
1 The second bullet on page 4-2 discusses the reliance on single plant-specific PRA quantitative results in selected areas.
Examples are provided for this type of application. An important example that is not included in this listing and should be are justifications for continued plant operation (JCOs).
An important point to note regarding the human interactions write-up in.
the second paragraph on page 4-7 is the methodology developed by EPRI that utilizes simulator data for human interaction rates.
Plant-specific operator training simulator exercises are observed and l
the data from these is used to calculate plant-specific human j
interaction rates. This methodology.is described in EPRI NP-6937, Volumes 1, 2 & 3, Operator Reli oility Experiments Using Power' Plant Simulators.
The last paragraph on page 4-7 and continued on page 4-8 discusses that the use of PSA may be more appropriately applied to the potential for, severe core damage or system availability tnan to public risk. This is certainly the case for most of the utilities who performed the minimum requirements for the IPE because, only a Level 1 PSA along with a containment analysis was performed i.e., a level 3 PSA vas not performed.
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Section 4.2.1 (page 4-12) and section 4.2.2 (page 4-13) discuss the elements of a PRA. The paragraphs that discuss initiating events do not mention steam generator tube ruptures or internal' floods as initiating events.
Both of these initiating events are included in current PSAs.
The Initiating Event Analysis portion of Section 4.2.2 (page 4-13) notes that Boolean models depicting various systems and components
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contributing to the initiating. event are generally not developed. This is not necessarily always the case.
For some B0P initiating events, like losses of specific /both trains of service water, component cooling water and makeup, Boolean models were developed and used as the basis for the initiating event frequency.
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Docket Number 50-346' License Number NPF-3
~ Serial Number 2163 4ttachment Page 2 Table 4.2-1 is confusing.
It seems to contain a lot of extra information if the only purpose is to identify some of the plant systems that are modeled in the PSA and those that are not.
In some cases, the' systems that are identified in the table as not explicitly modeled or evaluated are not consistent with several PSAs.
For example, most PSAs do explicitly model component cooling vater,. normal service water and required ventilation systems.
Page 4-30 discusses how often the PRA needs to be updated for specific PSA applications. While it is certainly reasonable to update the PSA following an outage or in response to a specific design change, it is unreasonable to make it 'real-time driven'. This is especially true of-the plant specific data analysis.
Each application should consider the status of how up-to-date the PSA is; in the majority of cases, a
' real-time driven' PSA is not necessary.
On the top of page 47, an equation is provided that calculates the maximum pre-determined A0T extension for any single SSC. An example using real component data vould oe helpful; it is not obvious that the denominator vould end up as a positive number.
Differentiation needs to he clarified with respect to PSA application criteria for one-time changes or exemptions and those that will be implemented permanently.
As discussed in several sections of this report, the PSA application criteria (sections 4.4, 4.5 and 4.6) will need to be applied in several pilot studies before it is implemented.
Pilot studies are necessary to evaluate the existing review criteria and further redefine the guidelines as appropriate.
Furthermore, similar to the efforts involved in maintaining a 'living' PSA, this Risk Application Technology will need to be updated to take into account new applications and criteria along with new state-of-the art PSA techniques and methodology.
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