ML17244A908
| ML17244A908 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/21/1978 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML17244A909 | List: |
| References | |
| IEB-78-04, IEB-78-4, NUDOCS 7904280003 | |
| Download: ML17244A908 (16) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.
C.
20555 IE Bulletin No. 78-04 Date:
February 21, 1978 Page 1 of 3 ENVIRONMENTAL QUALIFICATION OF CERTAIN STEM MOUNTED LIMIT SWITCHES
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INSIDE REACTOR CONTAINMENT Description of Circumstances:
As a result of a recent review by Westinghouse of the seismic and environ-mental qualifications of the electrical circuitry used for valve opera-tion,'ertain stem mounted limit switches (SMLS) associated with various safety related valves were found not to be environmentally qualified for loss of coolant accident (LOCA) conditions.
The switches in question are installed on certain motor operated valves and certain air-operated valves located in primary containment.
The functions of these valves provide either containment isolation or emergency core cooling system (ECCS) al'ignment during accident conditions.
Westinghouse has stated that for air operated valves the SMLS function is to provide "latch-in" capability to the actuation control circuitry of the valve.
It therefore is designated as safety-related and must receive seismic and environmental qualification.
The'oncern arises if the SMLS contacts short circuit during LOCA'ondi-tions. If this occurs and if the valve control switch is in the "AUTO" position (and control air is available to the valve operator),
the valve will move from its post accident position to the normal operating posi-tion when either the safety injection or containment isolation signal is reset.
A limited number of the switches are also used in safety related motor operated valve circuits in Westinghouse designed plants.
The attached Westinghouse Technical Bulletin, NSD-TB-77-13 issued on September 30, 1977, further describes the problem and provides sugges-tions for correcting the problem in air-operated valve actuation circuitry.
One of the corrective actions considered by Westinghouse involves replace-ment of the switch with a switch that is envir'onmentally qualified.
An alternative corrective action utilizes a circuit modification to the "latch-in" feature associated with the air-operated valve circuitry so that no adverse affect on valve operation can occur during post accident
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IE Bulletin No. 78-04 Date:
February 21, 1978 Page 2 of 3 conditions.-
For example, VEPCO has initiated a modification to the valve control circui'try at North Anna to remove the SMLS contacts from the valve operation circuitry.
The SMLS in question is identified as NAMCO Model D2400X or EA-170-302 SNAP LOCK.
NAMCO can provide qualified switches to replace unqualified ones upon request from the user.
-Because all NAMCO SNAP LOCK type switches have been seismically qualified by tests, only environmental qualification is a concern in this issue.
This problem may be generic for all power reactor, facilities with an operating license or a con-struction permit.
Action to be Taken by Licensees and Permit Holders; For all power reactor facilities with an operating license or a construction permit:
Determine if your facility utilizes or plans to utilize NAMCO D2400X or EA-170-302 SNAP LOCK switches in any safety related equipment in the primary containment, including the valve control circuitry previously discussed.
2.
If any such applications are identified, review these applications to determine the adequacy or qualification testing for these switches and submit the qualification documentation or references to NRC for review.
3.
If evidence is not available to support a-conclusion of adequacy, submit your plans and programs, including schedules, for corrective action.
4..
Provide your response in writing within 30 days for facilities holding an operating license and within 60 days for those facili-ties with a construction permit.
Reports should be submitted to the Director of the appropriate NRC Regional office and a copy should be forwarded to the U. S. Nuclear Regulatory Commission, Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Washington, D.
C.
20555.
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IE Bulletin No. 78-04 Date:
February 21, 1978 Page 3 of 3 t
Approved by GAO, B180225 (R0072); clearance expires 7/31/80.
Approval was given under a blanket clearance specifically for identified generic problems.
Attachment:
M Technical Bulletin NSD-TB-77-13
Westinghouse Nuclear Set VICe alviss 0fj Technical Buffetin
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'vr h use su lied Hucfear
. An advisor notsco of a recent technical development per ainjnri to the installation or operation st Westinghouse supphed Hucfear irfent equipment.
Recipients should evaluate the information and rooommencfotion, and initiate action where epproprixte-t.o.~ 2725, Finxburoh. PA 15'iect Safet Related Stem Mounted t.imit Switches System(s)
Safet Related Air 0 crated Ualve Control Circuits
'ffected Plants All Number NSQ.TB-Data Se tefnber 30,'1977 S D.N References POE-SO-144 (Para hrased Below)
Sheet 1
2 The following paragraphs describe a possible safety problem based on the use of seis-mically>>d environmentally unqualified limit switches in control circuits of safety related valves-The limit switches are mounted on the stems of air operated valves as a lock-in/lock-out feature in these valves.
As these limit switches are unqualified, it is possible to postulate a cormon nude failure in the post seis-mic or Post accident environment.
If the limit switch.ails closed (shorted),
an unsaf or unwanted position of the air operated valves will occur when resetting the>>SI" or "T" signal provided that the air supply is still available to the valves.
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The air operated valve solenoid control circuit consists of' three position switch (Open-Auto=Close) in which the "Auto" position circuit has the stem-mounted limit switch contact and the>>SI" or "T" signal contact as shown in Figure 1
(Normal Operatin Condition),
t'hen an>>SI>> or>>T" is initiated, the s'olenoid is de-energized, causing the valve to close.
When the>>SI>> or>>T" signal is reset, normally, the limit switch contact Mould be open and prevent the valve
>rom reopening.
Ef failure of tl~ limit switch is'postulated (contacts shorted),
due to post seismic or post accident environ-mental conditions, the valve would be repositioned open upon resetting the >>SI" or "T" signal o
Close 125 VDC Auto Open
>>SI" or>>T>> signal - when no signal ls
- present, contact is closed.
Stem-mounted limit switch contact-cl.osed when valve is fully open.
Solenoid - energize to open Addirional )nforrnaticn, if Renuired. may be Obtained from the Ori inator. Teieohone 412-25 -5409 gn inatyr.
or OVlfi) 236 -5409 pror J.
P. Tobin Pro ects 4 Reaional Su mort S.
G. Caslake, Nanager Electric Service
Some 2.
3.
considerations to correct this problem are:
Replace the limit switches with seismically and environmentally qualified limit switches, At the present
- time, we are inves~igating the feasibility of qualifying limit switches Chat are available.
Procedurally require operators to place the appropriate control switches in the "close" position prior to resetting the "SI" or "T" signal.
By following thisprocedure, the v'alve would not move to an unwanted position even if the stem mounted limit switch failed.
Depending upon the individual plant arrangement, another solution is possible.
For example, at Farley an alternative would be to delete the limit switch function and provide a separate "SI" or "T" signal reset for these valves.
A separate reset is already used in connection with the Far'ley switchover procedure for the PHR suction valves and could be used for this purpose.
Still another alternative would be to have a separate reset for the appropriate limit switch circuitry, Vestinghouse has notified the HRC of this condition (NS-CE-1489, 8/19/77),
and recomrznds that all plants review their safety related air operated valve control circuits.
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IE Bulletin No. 78-04 February 21, 1978 ENCLOSURE 2
LISTING OF IE BULLETINS ISSUED IN 1978 Bulletin Subject No.
Date Issued Issued To 78-01 78-02 78-03 Flammable Contact-Arm Retainers in G.E.
CR120A Relays Terminal Block gualification Potential Explosive Gas Mixture Accumula-tions Associated with BWR Offgas System Operations 1/16/78 1/30/78 2/8/78 All Power Reactor Facilities with an Operating License (OL) or Construc-tion Permit (CP)
All Power Reactor Facilities with an Operating License
=-(OL) or Construc-tion Permit (CP)
All BWR Power Reactor Facilities with an Operating License (OL)
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89 EAST AVENUE, ROCHESTER, N.Y. 14649 KEITH W. AMISH EXECUTIVE VICE PRCCIDCNT TELEPHONE ARE+ COOE T>5 546 2700 February 10, 1978 Mr. Boyce H. Grier, Director U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region I 631 Park Avenue King of Prussia, Pennsylvania 19406
Subject:
IE Bulletin No. 78-02, Terminal Block Qualification R. E. Ginna Nuclear Power Plant, Unit No.
1 Docket No. 50-244
Dear Mr. Grier:
This letter is in response to IE Bulletin No. 78-02, requesting that we review the use of terminal blocks in safety related circuits inside containment.
Upon receipt of information regarding the terminal block testing by Connecticut Yankee Atomic Company, we reviewed the use of terminal blocks in safety circuits inside containment at Ginna and deter-mined that unprotected terminal blocks, manufactured by Buchanan, were used in the pressurizer pressure and level circuits.
Rather than attempt to locate qualification data, these terminal blocks have been replaced by Westinghouse model 542247 terminal blocks.
Documentation supporting the acceptability of these terminal blocks for service at Ginna is provided in the enclosures to this letter.
Very truly yours, Keith W. Amish Enc.
vc: Director, Office of Nuclear Reactor Regulation Director of Reactor Operations Inspection
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Docket No. 50-244 I
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION I
'631 PARK AVENUE KING OF PRUSSIA, PENNSYI VANIA 19406
'anuary 30, 1978
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I (C-&5 Rochester Gas and Electric Corporation ATTN:
Nr. Leon D. White, Jr.'ice President Electric and Steam Production 89 East Avenue Rochester, New York 14649 Gentlemen:
Enclosed is IE Bulletin No. 78-02 which requires action by you with regard to your power reactor facility(ies) with an operating license or a construction permit.
Should you have questions regarding this Bulletin or the actions re-quired of you, please contact this office.
Sincerely,
~gc677.
Director
Enclosures:
l.
List of IE Bulletins Issued in 1978 cc w/encls:
L. S.
Lang, Plant Superintendent J.
W. Witte, gC Engineer Lex K. Larson, Esquire
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