ML20032B865
| ML20032B865 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek, Cooper, Arkansas Nuclear, River Bend, Waterford, South Texas, Comanche Peak, Fort Calhoun, Fort Saint Vrain  |
| Issue date: | 07/22/1981 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | ARKANSAS POWER & LIGHT CO., GULF STATES UTILITIES CO., HOUSTON LIGHTING & POWER CO., KANSAS GAS & ELECTRIC CO., LOUISIANA POWER & LIGHT CO., NEBRASKA PUBLIC POWER DISTRICT, OMAHA PUBLIC POWER DISTRICT, PUBLIC SERVICE CO. OF COLORADO, TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 8111060460 | |
| Download: ML20032B865 (2) | |
Text
{{#Wiki_filter:, ./ 'o,, UNITED STATES 8 NUCLEAR REGULATORY COMMISSION
- s. y, g4 REGION IV Q,
[ 811 RYAN PLAZA DRIVE. SUITE 1000
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ARLINGTON, TEXA8 780,11 j July 22, 1981 Gentlemen: The enclosed IE Circular is forwarded for your appropriate action. No written respense to this circular is required. .T you have any questions related to this matter, please contact this office. Sincerely, 4 ' ly Karl V. Seyfri Director
Enclosures:
1. IE Circular No. 81-12 2. List of Recently Issued IE Circulars l l h q twwwam PDR l
IE CIRCULAR 81-12 Licensee Facility / Docket Number Arkansas Power and Light Conpany Arkansas Nuclear One, Unit 1 & 2 Little Rock, Arkansas 50-313; 50-368 Nebraska Public Power District Cooper Nuclear Station Columbus, Nebraska 50-298 Omaha Public Power District Fort Calhoun Station Omaha, Nebraska 50-285 Public Service Company of Colorado Fort St. Vrain Generating Station Denver, Colorado 50-267 Gulf States Utilities River Bend Beaumont, Texas 50-458; 50-459 Houston Lighting & Power Company South Texas Project Houston, Texas 50-498; 50-499 Kansas Gas & Electric Company Wolf Creek Wichita, Kansas STN 50-482 Louisiana Power & Light Company Wa terft.rd-3 New Orleans, Louisiana 50-382 Texas Utilities Generating Company Comanche Peak Steam Electric Station Dallas, Texas 50-445; 50 ',46
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SSINS No.: 6830 Accession No.: 8103300406 IEC 81-12 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 IE Circular No. 81-12 July 22, 1981 Page 1 of 2 INADEQUATE PERIODIC TEST PROCEDURE OF PWR PROTECTION SYSTEM ,D e se-an of Circumstances: mber 30, 1980, ground isolation procedures were being carried out to u-i.m..a an electrical ground in the 125V de bus No. 1 at the St. Lucie Nuclear Power Plant. Part of the procedure requires deenergizing the dc control power to the reactor trip circuit breakers (TCBs). These breakers are desig,,ed to trip (fail-safe mode) on undervoltage upon loss of de control power. Referring to Figure 1, the four TCBs (TCB 1,3,5, and 7) that are supplied control power from dc bus No. 1 did not trip immediately (because of binding) on undervoltage when control power was deenergized. The operators did verify that the shunt trip for each of the four TCBs was functioning. Operators also verified that the redundant TCBs from dc bus No. 2 (TCB 2,4,6, and 8) tripped on similar undervoltage conditions, and, in fact, inadvertently caused a plant trip while testing. Investigation into the problem by the 'icensee identified the cause of failure as an out-of-adjustment condition in the linkage mechanism of the undervoltage trip device. This adjustment problem, together with the lack of cleaning and periodic relubricating of the trip shaft mechanism, is the subject of IE Bulletin 79-09 which was issued April 17, 1979. While shutdown, the undervoltage trip mechanism on each of the above four faulty TCBs was adjusted and verified to operate satisfactorily. Investigation by the licensee revealed that the reactor protection system (RPS) periodic test procedure in use at the time did not verify the trip function of the undervoltage trip coil independent of the shunt trip coil. Referring to l Figure 1, it can be set, that during a reactor trip test at this facility, tnese coils operate simultaneously causing the trip opening of the associated TCBs. This arrangement of the RPS and the trip test procedure may be similar for other PWRs. BWRs may use similar circuit breakers in safety systems; therefore, similar i indequacies in their circuit breaker test procedures may exist. Following adjustment of the linkage mechanism of the undervoltage trip device l the licensee instituted a revised surveillance test procedure to check the under-l
~. .~ IEC 81-12 July 22, 1981 Page 2 of 2 voltage and shunt trip devices independently and to insure proper breaker operation. Although not shown in Figure 1, the undervoltage trip coil and the shunt trip coil are separately fused so that test procedure changes resolved the problem at St. Lucie. Recommended Action for Holders of Operating Licenses and Construction Permits: It is recommended that holders of operating licenses and construction permits review for applicability the specific items presented in the " Description of Circumstances." It is further recommended that the procedure for surveillance testing of trip circuit breakers be reviewed and revised as necessary to provide independent testing of each trip function, including position verification to ensure that the breaker actually trips. If the trip circuit breakers do not have provisions for independent testing of each trip function, including position verification, then appropriate modifi-cations should be made to include suc's features (e.g., local rushbuttons for the shunt and undervoltage trip coils, separately fused circuits for the shunt and undervoltage trip coils, etc). No written response to this circular is required. If you need additional information with regard to this subject, please contact the director of the appropriate NRC Regional Office.
Attachment:
Simplified Functional Diagram of the Redctor Protective System (Figure 1)
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IE Circular No. 81-12 July 22, 1981 RECENTLY ISSUED IE CIRCULARS Circular Subject Date Issued To No. Issued 81-05 Self-Aligning Rod End 3/31/81 All power reactor facilities Bushings for Pipe with an Operating Licenses Supports (0L) or Construction Permit (CP) 81-06 Potential Deficiency 4/14/81 All power reactor facilities Affecting Certain with an Operating License Foxboro 10 to 50 (OL) or Construction Permit Milliampere Transmitters (CP) 81-04 The Role of Shift Tech-4/30/81 All power reactor facilities nical Advisors and Impor-with an Operating Licenses (0L) tance if Licensee Event or near-term Operating Licenses (OL) Reports 81-07 Control of Radioactively 5/14/81 All power reactor Contaminated Material facilities with an Operating License (0L) or Construction Permit (CP) 81-08 Foundation Materials 5/29/81 All power reactor facilities with an Operating License (0L) or Construction Permit (CP) t 81-10 Steam Voiding in the 7/2/81 All power reactor fa:ilities i Reactor Coolant Systein with an Operating License (CL) during Decay Heat Removal or Construction Pernit (CP) Cooldown Enclosure l l t}}