ML18018B230

LER 77-020-00 for Dresden Unit 2 Regarding an Incident Where an Alarm Was Received on the Service Water Radiation Monitor After the 2A Ccsw Pump Was Started

ML18018B230
Person / Time
Site:	Dresden
Issue date:	06/28/1977
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS Ltr. #77-572 LER 77-020-00
Download: ML18018B230 (8)

Text

NRC FORM 195 U.S. NUCLEAR REGULATO MMISSION DOCKET~UMBgJ3

{2-76)

FILE NUMBER NRC DISTRIBUTION FQR PART 50 DOCKET MATERIAL TO: FROM: DATE OF DOCUMENT Commonweal th Edison Company 6/28/77 Mr. James G. Keppler Morris, Illinois DATE RECEIVED B, B Stephenson 7/13/77 ETTER ONOTORIZED PROP INPUT FORM NUMBER OF COPIES RECEIVED RIG INAL C LASS IF IE D 0 COPY DESCRIPTION ENCLOSURE Licensee Event Report (RO 50-237/1977-20) on 5/29/77 concerning an alarm being received on gg<SL<~@tI the service water radiation monitoro ~ ~ ~ ~ ~ ~ ~ ~ ~

PLANT NAME: (2-P)

Dresden-Unit No, 2 R JL 7/13/77 DOHOT REMOVE NOTE: IF PERSONNEL EXPOSURE IS INVOLVED SEND DIRECTLY TO KREGER/J. COLLINS FOR ACTION/INFORMAT ON INTERNAL DISTR I BUTION LITO E TERNAL DISTRIBUTION CONTROL NUMBE R 771940232 ACRS 16 SENT AS AT B NRC FORM 195 (2-76)

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Commo lth Edison Dresden Nuc r Power Station R.R. g1 Morris, Illinois 60450 Telephone 815/942-2920 BBS Ltr. i/ 77-572 June 28, 1977 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations Region III File U. S. Nuclear Regulatory Commission 799 Roosevelt Road

.Regulator Docket Glen Ellyn, Illinois 60137 Enclosed please find Reportable Occurrence report number 50-237/1977-20.

This report is being submitted to your office in accordance with the Dresden Nuclear Power Station Technical Specifications, Section 6.6.B.

B. Stephenson Station Superintendent Dresden Nuclear Power Station BBS:sm Enclosure cc: Director of Inspection 6 Enforcement Director of Management Information & Program Control File/NRC Wp OL JOL ] 1977

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I LICENSEE EVENT REPO CONTROL BLOCK: (PLEASE PRINT AI.L REQUIRED INFORIVIATION) 1 UCENSEE UCENSE EVENT NAME LICENSE NUMBER TYPE TYPE

~01 2 LD R S 2 0 01 0 0 00 0 0 0 4 L 2 2 1 ~03

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7 89 14 15 25 26 30 31 32 REPORT REPORT CATEGORY TYPE SOURCE DOCKET NUMBER EVENT DATE AEPOAT DATE tOOijOONT L ~L 0 5 0 0 2 3 7 0 5 '29 7 7 0 6 2 8 7 7 7 8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION 7

7 7

I Qo g 8 9 8 9

[OD4]

8 9 During normal plant operation, started to rovide Torus cooling through the erform a monthl . HPCI surveillance 2A Containment Cooling Service Water(CCSW) pump was DOS 2300-1.

2A LPCI heat exchanger Immediatel after the in order to 2A CCSW pump 80 80 toOI ation monitor. The 2A 7 8 9 80 I00I CCSW pump TTas shutdown and the heat exchanger loop containing the pump (the 2A-1503 7 89 FAME 80 SYSTEM CODE CAUSE CODE COMPONENT CODE COMPONENT SUPPUEA COMPONENT MANUFACTURER (continued) tODT] ~SF E H T E X 0 H N P 1 6 0 N 7 8 9 10 11 12 17 47 48 CAUSE DESCRIPTION

.[ODs] An increase from 350 cps to 3000 cps on the service water radiation monitor was an 7 8 9 80

[Q8 9 indication of a tube leak in the 2A-1503 LPCI containment cooling heat exchanger. An 7 ~ 80

[110] investigation revealed the fact that 14 of the 2510 tubes in the heat exchanger were 7 89 80 METHOD OF FACIUTY STATUS POWER OTHER STATUS DISCOVERY DIscovERY DEscAIPTIDN (continued) t111] ~E ~08 0 NA B NA 7 8 9 10 12 13 44 45 46 80 FORM OF ACTIVITY COATENT RELEASEO OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE Qg L M 1.12 x 10 1 Ci Reactor building to service water 7 8 9 10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION

~00 0 ~Z NA 7 89 11 12 13 80 PERSONNEL INJURIES DESCRIPTION NA 7 8 9 11 12 Bn OFFSITE CONSEQUENCES NA ~IT Qg 7 8 9 LOSS OR DAMAGE TO FACILITY TYPE DESCRIPTION

~1 Z NA I 7 89 10 80 PUBLICITY NA I 7 89 BII ADDITIONAL FACTORS

~18 NA 7 89 7 89 NAME Desi Santanna PHONE. Ext, 265 GPO GblrGET

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EVENT DESCRIPTION continued) heat exchanger loop) was isolated. 2D CCSM pump was started and the other containment cooling heat exchanger loop tested to verify that it was operable. This event is not a repetitive occurrence though a subsequent investigation has indicated that small leaks may have occurred undetected in the-past. Because a redundant contain-ment cooling heat exchanger loop was operable safe plant operation was not impaired. (50-237/77-20)

CAUSE DESCRIPTION continued) leaking. Calculations to estimate the amount of radioactive material released were performed using the following parameters. The service water volume of the contain-ment cooling water heat exchanger is 4,340 gallons. The length of the release was conservatively estimated at 1.24 minutes. The circulating water flow at the time of the incident was 885,000 gpm.

The activity of the water on the service water side was conservatively assumed to be the same as the activity of the torus water. A gamma:isotopic, analysis of the D2 torus water revealed the concentrations of the following nuclides.

Cs 134 9.6 x 10 uCi/ml

. Cs 137 1 2 x 10 uCi/ml Co 58 1.8 x 10 uCi/ml Co 60 1.1 x 10 3 uCi/ml Mn 54 2.9 x 10 uCI/ml Using the above data, caloulations revealed that the sum of the ratios of these concentrations to the maximum permissible concentrations was 0.77. This indicates that the concentration in the circulating water canal to Dresden Cooling Lake was 77% of the applicable 10CFR 20 limits. This radioactivity was further diluted by the 1275 acres of water in the cooling lake.

A sample of the torus water has also been sent to a contractor for Strontium'nalysis.

The faulty tubes were plugged on both the top and bottom with 3/4" stainless steel tapered plugs. To verify that the plugs would be capable of withstanding operating pressure, the tubes were exposed to operating conditions (LPCI pump flow) which corresponds to a minimum of approximately 125 psig. This test was conducted for a period of 5 minutes with no anomalies observed. The heat exchanger is a type 6B-3222 heat exchanger manufactured by Berlin Chapman, a Division of Perfex Corporation and was built to ASME ill, Class "C" and the Tubular Exchanger Man-ufacturer's Association Class "R" Standards. The fact that there were leaking tubes in the LPCI containment cooling heat exchanger prompted an investigation into past service water radiation monitor records. The investigation revealed three instances when radionuclide releases went undetected. These previous releases occurred on 4-5-77, 4-24-77, and 5-10-77 and were of the same magnitude of the 5-29-77 release.

Procedures relevant to this type of occurrence shall be reviewed and;necessary changes made to prevent any recurrence of this event.

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