ML20206D758
| ML20206D758 | |
| Person / Time | |
|---|---|
| Issue date: | 10/25/1988 |
| From: | Butcher E Office of Nuclear Reactor Regulation |
| To: | Katz B SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 8811170262 | |
| Download: ML20206D758 (2) | |
Text
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OCT t S 99El Mr. Brian Katz
(
Southern California Edison Company P.O. Box 128 i
San Clemente, California 92672 j
l
Dear Brian:
l Thank you for the copies of pRA graphs you sent me f rom your Quarterly i
i Perforrt ce Monitoring Reports.
Based on our discussions of how you use these l
l graphs, it appears that your program shares some of the important concepts and objectives we are studying as a possible alternative or supplement to our I
current deterministic system of Technical Specifications.
[
As we have discusscd in the past, the NRC is reviewing systers in ut.e in other countries which could, at least in part, be applied in the U.S.
One of the l
more advanced systems we are stuoying is the ESSH which is oeing used on a trial basis in England.
Enclosed is a copy of a letter I recently sent to i
England to confirm the final arrangements for a visit to discuss the ESSF and l
how it is used.
l In this letter 1 stated my intention to invite a U.S. utility to join in these
?
discussions.
Based on your personal f amiliarity with these types of ritk and j
reliability concepts and your company's already apparent recognition of their i
usefulness in gaining insights into ways to i'aprove safety. I would like to l
invite you to join us.
I believe you could make an important contribution in bringing an operations perspective to the issues we will be discussing.
4 The enclosed letter includes the planned meeting dates and a list of topics to I
be addressed. Please let me know as soon as possible if you wish to join us.
i Again, thank you for the information you provided and I look forward to.
j continuing to exchange ideas on the subject with you in the future.
Sincerely.
Original Si2ned By:
Edward J. Batcher i
Edward J. Butcher i
j
Enclosure:
As stated l
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o OCT 2 5 SE I
Mr. Brian Katz Southern California Edison Company P.O. Box 128 San Clemente California 92672
Dear Brian:
Thank you for the copies of PRA graphs you sent ine f rom your Quarterly Perf ormance Monii.oring Reports.
Based on our discussions of how you use these graphs, it appears that your program shares some of the leportant concepts and objectives we are studying as a possible alternative or supplement to our current deterministic system of Technical Specifications.
As we have discussed in the past, the NRC is reviewing systems in use in other countries which could, at least in part, be applied in the U.S.
One of the more advanced syste;ts we are studying is the ESSM which is being used on a trial basis in England.
Enclosed is a copy of a letter I recently sent to England to conitrm the final arrangements for a visit to discut.s the ESSM and how it is used.
In this letter i stated my intention to invite a U.S. utility to join in these discussions. Based on your personal f amiliarity with these types of risk and reliability concepts and your company's already apparent recognition of their usefulness in taining insights into ways to improve safety, I would like to invite you to join us.
I believe you could make an important contribution in bringing an operations perspective to the issues we will be discussing, The enclosed letter includes the planned meeting dates and a list of topics to be addressed.
Please let me know as soon as possible if you wish to join us.
Again, thank you for the information you provided and I look forward to continuing to exchange ideas on the subject with you in the future.
Sincerely, j
Original Si3ned By:
Edward J. Batcher Edward J. Butcher
Enclosure:
As stated OlsTRIBUT10l4 i
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UNITED STATES NUCLEAR RECULATORY COMMISSION
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suAaHuseTON,C.c.seems r
OCT 211988 l
Mr. Peter D. Jenkins Safety Technology Engineer Generation and Construction Division Barnett Way Barwood, Gloucester GL4 7RS England Dear Mr. Jenkins; i
As we agreed in our earlier correspondence, Mr. Fischer of my staff met with Dr. Horne on September 23, 1988 to begin the exchange of ideas between our two organizations on risk-based Technical Specifications. This meeting was quite useful as the starting point for this exchange and I would like to take this opportunity to thank Dr. Horne for providing his time on short notice.
I subsequently D1ked tn Dr. Horne via telephone about our proposed trip to Based on the England and woulu like to confirm these discussions with you.
availability of Dr. Horne s'id the plant staff it was agreed that we could meet on hovember 28-30, 1988.
f Dr. Horne suggested that perhaps we could spend the first day at your of fices 1
in Gloucester where we could discus 2 Technial Specification programs in each l
of our organizations and learn more about the detatis of your ESSM computer code.
This could be followed by spending some amount of time Tuesday at the plant where we could see the actual set up of the ESSM and talk to operations We have left Wednesday morning open personnel about their use of the system.
for any discussions lef t over from the first two days and plan te go back to London Wednesday afternoon.
1 also told Dr. Horne that we would like to invite a representative of one of
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the utility corpanies that operate a nuclear power plant in the U. S. to partic-ipate in our meetings. Dr. Horne stated that he did not think this would be a problem and on that basis i intend to explore this possibility with a utility that is beginning to integrate principles similar to those the ESSM is based on into their operations.
To f acilitate our discussions we have put togeth:tr a Itst of questions or topics that we would like to discuss.
A copy of this list is enclosed.
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. Mr. Peter D. Jenkins I look Please let une know if these arrangements are acceptable to you.
forward to ineeting with you in the near future.
Sincerely.
Original Signed By:
Edward J. Batcher Edward J. Butcher. Chief Technical Specifications Branch U. S. Nuclear Regulatory Comission
Enclosure:
As stated cc: John Met. cod. Nll Dr. Brian E. Horne.CEGB Dr. Nigel J. Holloway. Nil Dr. Bahman Ateft. SAIC e
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SUGGESTED TOPICS FOR DISCUSS'ON 1,
Characteristics of the ESSM Level of Detail of the Plant Model incorporated in ESSM.
1.
Component Level Supercoeponent level Independent Subtree 2.
Methodology for Representation of the Plant Model, 1
Independent fault trees using support state methodology.
Merged system fault trees (1 large fa91t tree for each accident sequence).
One large fault tree representin't plant model.
3.
Calculation Methodology Regeneration of minimal cutsets in each calculation.
Manipulation of a large number of sequence cutsets generated
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1 with no component out of service.
Use of cutoff frequency.
4 Hardware Requirements Prirary Mt.nory Data Storage 5.
Speed of the Program Discussion of severa) actual cases.
Limiting cases.
6.
Data Used in Qualification of Plant Model Generic Plant Specific How often will it be updated?
Model used for unavailability of standby corponents (1/2 T) 7.
Modeling of Human Errors Cognitive human errors.
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Dependencies of human error on plant status i.e.,
availability of information. level of stress, time availability for taking actions.
Given unavailability of one component, does the model know which 8.
other componants or systems would also be out of service due to single components being common to more than one system.
How are support system interactions modeled and the impact of 9.
support system component maintenance outages evaluated?
10.
Are any of ESSM copsbilities specific to EGRS or is it general enough to be applied to any other plert,
- 11. Other Technical Specifications-Related issues Discussion of the ESSM Criteria Used for Assessment of Acceptable 1.
Allowed Outage Times Corpletely Probabilistic (i.e., maximum core melt frequency)
Probabilistic and Deterministic Delta Core Melt frequency How are the Current Surveillance Test Intervals Chosen?
2.
Deterministic Reliability-Based What Methods are Used for Setting Technical Specifications 3.
Requirements that Cannot be Handled by Plant Risk Model and ESSM?
Deterministic Partially Risk-Based What portion of the requirements can be handled using risk-based rethods?
111. Operational Interface with the Model Acceptance of Risk Based Technical Specifications by the 1.
I oper3 ting staff.
What is the process used for inputting changes to plant status?
2.
Nurber of authorized people Process for assuring accuracy of the changes 2
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Does this process help in assuring that only the correct 3.
components are taken out of service for test or maintenance?
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ESSM.controllad tag out Other control mechanisms 1
4.
How Often is the Model Updated?
Model based on average cor.9enent unavailabilities.
Frequent updating of the model based on actual unavailabilities of standby corponents.
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