ML20236J587

Forwards Responses to Questions Raised During 771006 Meeting in Bethesda,Md Re Review of Application for Amend 52 to Application for OL

ML20236J587
Person / Time
Site:	Diablo Canyon
Issue date:	10/14/1977
From:	Crane P PACIFIC GAS & ELECTRIC CO.
To:	Stolz J Office of Nuclear Reactor Regulation
Shared Package
ML20236J368	List: IA-87-214, Discusses ACRS 92nd Meeting on 671207-09.ACRS Completed Review of PG&E Application for Const of Nuclear Unit at Diablo Canyon Site.Facility Can Be Constructed W/O Risk to Public Health & Safety ML20236J366 ML20236J587 ML20236J622 ML20236J671 ML20236J804 ML20236J841 ML20236J985 ML20236K008 ML20236K057 ML20236K327 ML20236K351 ML20236K384 ML20236K422 ML20236K563 ML20236L228 ML20236L279 ML20236L316 ML20236L364 ML20236L420 ML20236L474 ML20236L565 ML20236L647 ML20236L689 ML20236L706 ML20236L724 ML20236L756 ML20236L787 ML20236L806 ML20236L866 ML20236L901 ML20236L922 ML20236L931 ML20236L986 ML20236M007 ML20236M024 ML20236M065 ML20236M681 ML20236M725 ML20236M744 ML20236M771 ML20236M777 ML20236N015 ML20236N032 ML20236N085 ML20236N115 ML20236N139 ML20236N193 ML20236N208 ML20236N255 ... further results
References
FOIA-87-214 NUDOCS 8708060214
Download: ML20236J587 (3)

Text

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PACIFIC GRAS AND E LE C T RI C C O M PANY

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s Mr. John F. Stolz, Chief g.. , f, .

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Division of Project Management 'K-Ql U. S. Nuclear Regulatory Commission g.%.p-h). . ) 0 Washington, D. C. 20555 4 l

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Re: Docket No. 50-275-

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Dear Mr. Stolz:

In further support of our application for an interim operating license for Unit 1 at our Diablo Canyon site, I enclose twenty copies of our responses to questions raised during the October 6. meeting at Bethesda, Maryland, on review of Amendment No. 52 to the Diablo Canyon operating license application.

Kindly acknowledge receipt of the above material on the enclosed copy of this letter and return it to me in the enclosed addressed envelope, y ry truly yours, .- m.

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• Enclosures I CC w/ enc.: Service List (

P.S. Enclosed are two copies only. The remainder will be sent to you on Monday.

8708060214 870729 PDR FOIA PDR CONNOR87-214

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8 INTRODUCTION AND

SUMMARY

During the review meeting which was held on October 6, 1977, a number.

of questions were asked by NRC staff personnel concerning the seismic risk study.

During the course of the meeting, the discussion clarified and expanded the material which was included in the study, and some of the questions were' resolved.

The purpose of this submittal is to review some of the questions already answered and to supply additional information which reselves questions that were not answered during the meeting. As - agreed with Mr. Allison, we have arranged

- this submittal in a simple question-and-answer format'in order to expedite the transmittal of the information~ .

The nature of the questions which were asked generally concerned the sensitivity of the results from the study to failure rates and models used as well as requestrfor more detail on our techniques, procedures, and data input. We have answered the questions on sensitivity in several ways. In some cases, specific items were covered in individur1 questions and answers through discussion. We have also carried out a cornputer re-analysis of the fault tree results for several suggested variations in data. We have provided a general analysis of the effects and uncertainties associated with meteorological assumptions and r:odels. Finally, we have provided a general sensitivity analysis of the total risk estimates in the study which considered hypothetical changes in '

varicus significant parameters. The conclusions reached from each of these 1

approaches are included in the answers to each question.

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q, In your analysis, you have concluded that the check valve problem is not of major importance in'your plant. Provide additional justification for - -

this conclusion, .

l A. Isolation of low pressure systems from primary system pressure and protection from LOCA is achieved in two ways: 1) by testing to verify closure of both check valves or 2) by having motor operated valves in

! series with the two check valves.

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For the residual heat removal (RHR) and safety injection (SI) inter-faces with the cold leg loops, both the "first off" check valves (8948A, B, C, and D) and the "second off" check valves (8818A, B, C, and D) are tested during primary sys tem heatup and pressurization to verify that they are properly seated. For the RHR and SI interfaces with the hot leg loops, only the "first off" check valves (8949A, B, C, and D) are tested to verify that they are properly seated. However, l these interfaces are also protected by closed motor operated valves 8703 for the RHR system and valves 8802A and B for the SI system. Note that valve 8703 was not shown on Figure 3-17.

For the charging system interfaces with the cold leg loops, only the "first off" check valves (8900A, B, C, and D) are tested to verify that they are properly seated. However, these interfaces are also protected by motor operated valves 8801A, 8801B, 8803A, and 8803B which can be closed in the event of a low pressure system rupture.

For the accumulator interf aces with the cold leg loops, both the "first off" check valves (8948A, B, C, and D) and the "second off" check valves are tested during primary system heatup and pressurization to verify that they are properly seated. (B45% A B,C6 4 D) 3 Testing procedures are detailed in the Diablo Canyon Surveillance Test Procedures No. V-5 (see attachment). Note that testing of accumulator check valves has not yet been incorporated into these test procedures.

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