ML19318C371

LER 80-018/01T-0:on 800611,feedwater Lines Found Leaking Directly Into Torus & Bypassing Detection Sys.Caused by Drywell Leakage Detection Sys Design Inadequacy.Tech Spec Leakage Limits Reduced.Limits & Detection Sys Under Review

ML19318C371
Person / Time
Site:	Vermont Yankee
Issue date:	06/25/1980
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19318C358	List: ML19318C357 ML19318C371
References
LER-80-018-01T, LER-80-18-1T, NUDOCS 8007010405
Download: ML19318C371 (2)

Text

f'7 773 V* , LICENSEE EVENT REPORT LER 80-18/lT (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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74 75 REPORT DATE 80 i 60 61 DOCAET NUMBER EVENT D ATE EVENT DESCRIPTION AND PROSABLE CONSEQUENCES h I O I 21D1 uring a planned drywell entry to investigate suspected reactor coolant leaks, operatoqs go,3, jobserved that leakage had developed in one of the feedwater lines. An orderly plant l

,o,,i gshutdown to cold conditions was immediately initiated. Further investigation of the l g g eakl revealed that a significant portion of it was flowing directly into the Torus vial lO is l lthe vent header. Since this flow path bypasses the drywell leakage detection system, l l 0 l 7 l lit was determined that this situation constitutes a condition not specifically considerg-

,o,g, ged in the Safety Analysis Report or the Technical Specifications. l 7 8 9 -

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_ 22 27 28 29 31 32 K N AC ON ON PL NT MET HOURS 22 SS IT FOR 8. SUPPLI MANUF ACTURE R lX lgl34X ]g (A Jg l 0l 0l 3l l lYl@ lNlg lNlg lGl0l8l0lg 3J 3b,_, l36Al@ 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS l i l O l lThe cause of the event is attributed to an apparent inadequacy in the design of the l li ii j ldrywell leakage detection system. The immediate corrective action will be to adminis- 1 i,,7; ltratively reduce the Tech. Spec. limits to allow only 2 1/2 gpm unidentified leakage I g land 12 1/2 gpm total reactor coolant system leakage. Plant leak detection capabilitieg i , ,4 i land the Tech. Spec. bases are being evaluated. (CONTINUED ON ATTACHED SHEET.) l 7 8 9 80 STA S  % POWER oTHE R STATUS otSCO RY DISCOVERv DESCRIPTION l1 15 l [D_J@ l0 l3 l5 l@l NA l l A l@l Operator Observation l A TIVITY CO TENT RELE ASED OF RELE ASE AMOUNT OF ACTIVITY LOCATION OF RELEASE W lZlh W @l 7 8 9 10 11 NA 44 l l 45 NA 80 l

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VTVYS1 05000271 LER 80-18/1T CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (CONTINUED) ,

The cause of this event is attributed to an apparent inadequacy of the drywell leak detection system to detect certain types of leaks in the manner in which it was designed. Vermont Yankee has evaluated the capa-bilities of plant equipment to detect drywell leaks, the bases for the leakage limits contained in the FSAR and Tech. Spec. bases and the ade-quacy of the administrative leakage limits instituted immediately after the event as described in LER 80-18/1P.

The results of this evaluation have indicated a need to increase dry-well leakage surveillance as follows:

1. Drywell floor drains will be monitored as required by Tech.

Spec. Section 3.6.C. The administrative limits which were reduced in half to 2.5 gpm of unidentified leakage and 12.5 gpm of total leakage will be continued,

. 2. Drywell equipment and floor drains will be monitored and an administrative action limit of 2 gpm increase above normal levels in any 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period will be imposed,

3. A torus volume monitoring program will be established along with investigarive action limits. This will be designed to detect and require action for an increase in torus volume which could be indicative of the 5 gpm reactor coolant leakage required by Tech. Specs.,

4. Drywell air temperature will be monitored to check for an un-expected rise of 6*F within any 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period.

The Containment Air Monitor (CAM) will continue to be used to monitor for airborne gaseous and particulate radioactivity.

In addition, the need for physical modifications to prevent bypassing of the drywell sumps will be evaluated, and if deemed necessary, will be installed by the end of the 1980 refueling outage.

If a permanent physical modification is made to correct the problem, we will return to the leakage monitoring program stipulated in the Tech-nical Specifications.

The above surveillance which will be fully implemented by July 3,1980, provides adequate assurance that leakage from the reactor coolant pressure boundary can be adequately detected in a timely fashion.

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