ML19309C403

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Responds to NRC 800223 Ltr Re Overpressurization & Rupture of Low Pressure Injection Sys Low Pressure Piping Due to Failure of Redundant Check Valves to Act as Pressure Isolation Barrier
ML19309C403
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 03/31/1980
From: Herbein J
METROPOLITAN EDISON CO.
To: Eisenhut D
Office of Nuclear Reactor Regulation
References
TLL-137, NUDOCS 8004080560
Download: ML19309C403 (2)


Text

. 1 Metropolitan Ethson Company

. , Post Othce Box 480 MnMietown, Pennsylvania 17057 717 9444041 wnier ,0. rect 0,ai Nurnber Ma rch , 1980 TLL 137 Office of Nuclear Reactor Regulation Attn: D. G. Eisenhut, Acting Director Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Sir:

Three Mile Island Nuclear Station, Unit I (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Primary Coolant System Pressure Isolation Valves This letter is in response to your letter dated February 23, 1980, concerning an overpressurization and rupture of the Low Pressure Injection System low pressure piping due to a failure of redundant check valves to act as a pressure isolation barrier.

ITD!

l. Describe the valve configuration at your plant and indicate if an Event V isolation valve configuration exists within the Class I boundary of the high pressure piping connecting PCS piping to low pressure system piping; e.g., (1) two check valves in series, or (2) two check valves in series with a MOV;

RESPONSE

1. Event V valve configuration is present in TMI-I in the Core Flooding System (CF) and the Low Pressure Injection System (LPIS). The Core Flooding System and the LPIS have an "A" and "B" train. Within the Class 1 boundary, the CF System is made up of two check valves in series (CF-V5A/B and CF-V4A/B). Within the Class 1 boundary the LPIS consists of two check valves (CF-VSA/B and DH-V22A/B) in series with an Engineered Safeguards normally closed motor operated valve (DH-V4A/B) .

l l ITEM

2. If either of the above Event V configurations exist at your facility, indicate whether continuous surveillance or periodic tests are being accomplished on such valves to ensure integrity. Also indicate whether valves have been known, or found, to lack integrity; and [o0 Is r/D 8004080%0 h 5E O

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D. C. Eisenhut TLL 137

RESPONSE

2. In the past, no testing has been performed to ensure the integrity of these check valves on an individual basis. Ilowever, TMI-I's ISI/IST submittal dated January 31, 1980 states that CF-VSA/S, CF-V4A/B and Dil-V22A/B will be given a functional pressure isolation bar*4a- test before or during the restart of TMI-I.

Integrity problean witn the valve seat hold-down device for the HPI pump discharge check valves (MU-V73A/73C) have been reported by Licensee Event Report No. 80-03/IP. As LER No. 80-03/lP states, Dii-V22A/B is identical to MU-V73A/73C in design for the seat hold-downs.

An inspection program and design study is being developed to determine the scope of the problem and plan corrective actions.

ITEM

3. If either of the above Event V configurations exist at your facility, indicate whether plant procedures should be revised or if plant modifications should be made to increase reliability.

RESPONSE

3. CF-VSA/B, CF-V4A/B and Dil-V22A/B will be tested for valve integrity and functionality as a pressure barrier whenever any of the above check valves are moved from the fully closed position. Tentatively, this will be accomplished by modifying the plant to allow placing reactor coolant system pressure on the upstream side of each of the check valves and monitoring the leakage on the downstream side. Procedures and plant modifications will be completed before December 31, 1980.

Sincerely.

n

) \* ffN J. C. lierbein Vice President Nuclear Operations JCll: DGM: hah .

cc: J. T. Collins