ML20065S350

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Forwards Revised Tech Spec Changes Allowing Installation of Mods to Meet License NPF-11,Condition 2.C.17 Re Small Line Break & Single ECCS Injection Check Valve Failure
ML20065S350
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 10/22/1982
From: Schroeder C
COMMONWEALTH EDISON CO.
To: Schwencer A
Office of Nuclear Reactor Regulation
Shared Package
ML20065S354 List:
References
5307N, NUDOCS 8211010192
Download: ML20065S350 (5)


Text

{{#Wiki_filter:_ _ _ _ N Commonw cith Edison

 ],                    c   .) One First National Plaza. Chicago, Illinois                              ,

O 7 Address Reply to: Post Office Box 767 j chicago, Illinois 60690* . October 22, 1982 Mr. A. Schwencer, Chie f Licensing Branch #2 Division o f Licensing U. S. Nuclear Regulatory Commission Washington, DC 20555 -

Subject:

LaSalle County Station Unit 1 Proposed Amendmen t t o NPF-11 Change Request NPF-ll/82-10 Supplemental Information NRC Docket No. 50-373 Re ference (a): C. W. Schroeder letter to A. Schwencer dated Augus t 19, 1982.

Dear Mr. Schwencer:

Reference (a) provided Commonwealth Edison Company's original request for a change in Technical Specifications to allow installation o f a modification to meet License NPF-ll, Condition 2.C.17. On September 27, 1982, Commonwealth Edison personnel C. W. Schroeder, G. R . Crane , J. C. Renwick, et al, had a telecon with Dr. , A. Bournia, et al, o f your staf f. The staff had proposed the I following accident scenario:

1. A small line break occurs inside the drywell.
2. The small line break, through pipe whip or steam impact, causes the f ailure o f the instrument line which feeds a i division's 4 pressure sensors for detecting reactor I

pressure less than 500 psig.

3. The small line break results in the drywell pressure reaching 1.69 psig, thus initiating the low pressure ECCS systems.

C) . 4. The broken instrument line, now at drywell pressure, causes the 4 sensors to indicate the reactor is at less than 500 psig, thus allowing the division's ECCS injection valves to i open.

5. The reactor remains at approximately 1000 psig because a small break does not result in significant depressurization.

O h$R P

m J . A. Schwencer October 22, 1982

6. A single f ailure o f one ECCS injection check valve then results in an inter-system LOC A.

Upon review of the above scenario, Commonwealth Edison personnel developed a revised logic. The attached sketches confirm the revised logic for the pressure interlock on the low pressure ECCS 's a t LaSalle . This interlock at 500 + 20 psia replaces the prior differential pressure permissive which the NRC rejected during SER reviews. The sketches indicate physical separation o f the instrument sensing lines for the replacement pressure switches. This prevents satisfying the interlock logic in a single electrical division by a single sensing line failure. The LPCS, and each of the three RHR loops, has a dedicated pressure ser 7r whose signal (on low pressure) closes a series switch in the inte .ock logic. The other series signal to complete the logic and open the interlock is either or both pressure sensors mounted on instrument 14A. As indicated on the sketch and explained in the reference telecon, the logic is (1:2 plus 1:1) duplicated in redundant electrical divisions corresponding to the ECCS electric power divisions. The sketches also indicate that the former annunciation contacts from the differential pressure permissive are now utilized for this ECCS low pressure interlock annunciation via K8. The annun-clation that the low pressure interlock condition has been met is adequate operational information because the injection valve and system parameters for each low pressure ECCS independently confirm successful ECCS operation. This design concept fulfills licensing Condition 2.C. (17) of NPF-11 for LaSalle and it is consistent with Edison's commitment. The design approach has minimized wiring and hardware changes to enable a rapid change to the pressure interlock. The time require-ments associated with this change are also minimal. GE has performed an additional ECCS accident analysis to determine the impact of the modification on the predicted peak clad-ding temperatures. The mocification of the injection valve logic causes an additional delay to the opening of the ECCS injection valves. The results of the analysis show that for a valve opening time of 20 seconds, the delay in the ECCS injection causes only a 1.6 second delay in core reflooding and a corresponding increase in the peak cladding temperature o f 100F. There is sufficient margin in the LaSalle FSAR analysis to absorb the temperature increase and remain within the PCT limit o f 22000F. The modification is there-fore acceptable from an ECCS viewpoint.

w q . A. Schwencer

                                                  .3 -                 October 22, 1982
                   ' Attached are revised technical specifications to implement this change. This revision has been approved by Commonwealth Edison On-Site and O f f-Site Re view.

NOTE: THIS TECH SPEC CHANGE MUST BE EFFECTIVE ONLY UPON COMPLETION OF THE INST ALLATION OF THE MODIF IC A T 10 N . Three (3) signed originals and thirty-seven (37) copies o f this transmittal and attachments are provided for your use. If there are any questions regarding this matter, please contact this office. Very truly yours, s

                                                                / o /2.2 / 82_

C. W. Schroeder Nuclear Licensing Administrator 1m Attachments cc: NRC Resident Inspector - LSCS SUBSCRIBE 0 and SWORN to be fore me this c$,7adday a f /f tfr-/u d , 1982 Ow twa. Or n,& No tary Public 5307N 1

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