ML19341C239

Forwards Revised Supplemental Info Sheets for LER 79-050 Re Unplanned Reactivity Insertion.Caused by Mechanical, Personnel & Procedural Error.Valve Mu 39 Disassembled & Gaskets Installed

ML19341C239
Person / Time
Site:	Davis Besse
Issue date:	02/18/1981
From:	Murray T TOLEDO EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
L81-126, RO-79-050, RO-79-50, RO-NP-32-79-06, NUDOCS 8103020509
Download: ML19341C239 (3)

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e EDISON Fsbruny 18,!1981 L81-126 FILE: RR 2 (NP-32-79-06)

. Docket No. 50-346 i License No. NPF-3 l Mr. Ja=es G. Keppler Regional Director, Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Co=::tission

'799 Roosevelt Road Glen Ellyn, Illinois (0137

Dear Mr. Keppler:

Enclosed.are three copies of the Supplemental Information Sheets for LER 79-050, which have been revised. The revisions to'the sheets are indicated by a "1" in the left margin of each page. There has been no change to the Licensee Event Report

~ Form 366.

Please replace your previous copies of the supplemental information for LER 79-050 with the attached' revision.-

Ycurs truly, Imb Tarry D. Murray Station' Superintendent Davis-Besse Nuclear.Powcr Station .

TDM/ljk

-Enclosure.

cc: Mr. Victor Stello,-Jr.,- Director Office of Inspection and Enforcement Enc 1: 30 copies

.Mr. Norman-Haller, Director Office of Management Program Analysis Encl: 3 copies Mr. Luis Reyes

'NRC ResidentiInspector Encl: 1 copy 4

- THE TOLEDO EDISON COMPANY - EDISON PLAZA 300 MADISON AVENUE TOLEDO. OHIO 43C52 f 01;cae20507 - ,  ;

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d TOLEDO EDISON COMPANY ,

DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFOPJtATION FOR LER NP-32-79-06 DATE OF EVENT: April 23, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Unplanned reactivity insertion greater than 0.5%

f K/K 4

Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MhT) = 0, cnd Load (Gross MWE) = 0.

Description of Occurrence: After Reactor Coolant Pump (RCP) 1-2 seal repairs were completed. Davis-Besse operations personnel commenced the Reactor Coolant System (RCS) fill at 1905 hours0.022 days <br />0.529 hours <br />0.00315 weeks <br />7.248525e-4 months <br /> on April 21, 1979. It was planned that 47,000 gallons of

. water from Clean Uasta Receiver Tank (CURT) 1-1 (1237 ppm boron concentration) would be pumped into the RCS (1259 ppm boron concentration) to achieve a final RCS boron concentration of 1246 ppm.

Midway through the fill, at 0950 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.61475e-4 months <br /> or. April 22, 1979, the Davis-Besse Chem Lab reported that the RCS boron concentratica was 1198 ppm. Operations personnel immed-intely verified that the decay heat flow w>s greater _than 2800 gpm, per Technical Specification 3.1.1.2,and requested another RCS ss=ple to verify the boron concen-tration reported at 0950 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.61475e-4 months <br />. At 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />, the Chem Lab reported that the bcron cencentration of the second sample was 1A94 ppm, essentially the same as the first cample.

At 1125 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.280625e-4 months <br /> on April 22, 1979, the RCS fill was stopped to find the cause of the RCS boron concentration reduction. During this. time, Boron Batch Flow Controller Velve MU 39. was leak checked and found to be closed tight. This valve was checked bicause it has been known to-Icak before. An information tag had been hung at the Btron Batch Flow Controller which read: "MU 39 leaks through; maintenance work request submitted 2-26-79". As of April 22,1979, _this work had not been completed, and this information tag was still in force. As an additional precaut.fon, Dem1nera-lized Water to Primary Makeup System Isolation Valve DW 66, which supplies deminera- i l lized water to MU 39, was also closed. Additional samples were taken from the RCS ,

cnd CWRT 1-1. The boron concentration for these samples were 1196 ppm and 1226 ppm,  !

respectively. Since the RCS boron concentration had stabilized and the CWRT.1-1 l boron concentration was essentially the same as before the fill, the RCS fill was j r:sumed at 1225 hours0.0142 days <br />0.34 hours <br />0.00203 weeks <br />4.661125e-4 months <br /> on April 22, 1979. At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, the RCS fill was complete.

On April 23, 1979, the Chem Lab verified that the RCS boron concentration was 1203 ppm. 11U 39 was leak checked again and this time'it failed. At 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br /> on April 23,zl979, the Davis-Besse Technical Section verified that deborating from 1259 ppm

[~ to'1198 ppm had caused an ' unplanned reactivity change of + 0.59% lin/K and estimated j L' that 3000 gallens of demineralized water had inadvertently entered the RCS. Techni-

~~~~Tcal Specification 6 .9. .1. 8 d requires that'when the reactor is subcritical, an un-planned reactivity _ insertion of more - than 0.5% 6 K/K is reportable.

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LER 179-050 t

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o TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-32-79*-06 J

Designation of Apparent Cause of Occurrence: This incident was caused by a combina-tion of mechanical, personnel and procedural error. MU 39 had experienced inter-mittent leakage problems prior to the incident. Scheduling problems prevented the repair of the valve between the initial identification of the problem with the work request and the time of the incident.

Evidence of intermittent leaking was experienced during the RCS fill. MU 39 was leaking when the fill was started on April 21, 1979, but did not leak on April 22, 1979, when it was leak checked. Again, it laaked on April 23, 1979 when the second

, leak test was performed. An operator, when lining up CWRT 1-1 to the RCS, failed to take appropriate action regarding the information on the information tag. " Filling and Venting of the RCS" SP 1103.02 did nor instruct station personnel to obtain RCS boron concentration informaticr. during the fill. This information could have indica-ted that demineralized water was inadvertently entering the RCS before any technical ,

specifications were violated.

Analysis of Occurrence: There was no danger to the health and safety of the public

-or to station personnel. Although the RCS boron concentration dropped to 1198 ppm, 3

the 0.59% A K/K reactivity insertion still resulted in a shutdown margin substantially greater than the required 1.00% d K/K shutdown nargin.

Corrective Action: When th'e RCS boron concentration was verified to be 1198 ppm, the RCS fill.was stopped, and the cause of the boron dilution was investigated. Boron Batch Flow Controller. Valve MU 39 and Demineralized Water to Primary Makeup System Isolation Valve DW 66 were closed. The RCS fill was resumed when the RCS boron con-centration stabilized.-

Und'er Maintenance Work Order 79-1586, MU39 was disassembled, the seatinE surface 1

Polished, new gaskets' installed, and the valve reassembled.- No further leakage de-tected as of May 4, 1979. Only normal seat wear observed before repair. Modifica-tion T-3751 to Filling and Venting of the RCS Operating Procedure, SP 1103.02, has been' written to close DW-66, in addition to MU 39, when lining up a CWRT to the RCS for filling.. The incident will be reviewed with all operations personnel.

" Filling and Venting of the RCS Operating Procedure", SP 1103.02 is being modified to include sampling the RCS boron concentration at four hour intervals during the

. fill and immediately stopping the fill and investigating if any RCS boron concentra-tion problems arise.

' Additionally,^ scheduling of equipment maintenance will be more closaly coordinated between operations and maintenance persor..a1 to complete repairs in a timely basis.

Failure Data

.There has been one previously reported similar incident, refer to Licensee Event Repot t NP-33-77-02.

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.LER #79-050'

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