PNO-III-97-043, on 970509,licensee Began Shutting Down Reactor Pending Replacement of Strainers on Suction Lines from Pressure Suppression Pool (Torus) to Various Eccs. Decision to Shutdown & Replace Strainers Made by Licensee

PNO-III-97-043:on 970509,licensee Began Shutting Down Reactor Pending Replacement of Strainers on Suction Lines from Pressure Suppression Pool (Torus) to Various Eccs. Decision to Shutdown & Replace Strainers Made by Licensee

ML20140G694
Person / Time
Site:	Monticello
Issue date:	05/09/1997
From:	Ring M, Schweibinz E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-97-043, PNO-III-97-43, NUDOCS 9705120101
Download: ML20140G694 (1)

i May 9, 1997 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-III-97-043 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as ir'tially received without verification or evaluation, and is basically all that is known by Region III staff (Lisle, Illinois) on this date. 1 Facility Licensee Emergency Classification i

Northern States Power Co. Notification of Unusual Event 1 Monticello 1 Alert Monticello, Minnesota Site Area Emergency i

Dockets: 50-263 General Emergency X Not Applicable

Subject:

SHUTDOWN TO REPLACE TORUS STRAINERS ON ECCS SUCTION LINES At 1 p.m. on May 9.1997, the licensee began shutting down the reactor pending replacement of strainers on the suction lines from the pressure l suppression pool (torus) to various emergency core cooling systems

(ECCS).

l

! The strainers are being replaced as a result of discussions between the l licensee and the NRC staff on the effects of strainer clogging under i certain specific accident conditions outside the original license basis.

In a large break loss of coolant accident, fibrous insulation material from the containment could clog the strainers and diminish the low-pressure ECCS system flow below that required.

The decision to shutdown and replace the strainers was conservatively made by the licensee.

The existing strainers on each of four suction lines are a truncated cone design about 17 inches in diameter and 10 inches long. Each strainer will be replaced with two larger strainers, each of which is 40 inches in diameter and 84 inches long. The licensee has issued a contract for the new strainers. Fabrication and delivery may take up to three months with an additional three weeks required to install the new strainers. The plant will remain shutdown until the replacement is completed.

The State of Minnesota will be informed. The information in this preliminary notification has been reviewed with licensee management.

l The licensee intends to issue a news release on the shutdown.

l l

Region III (Chicago) was notified of the shutdown by the licensee at 10:45 a.m. (CDT) on May 9,1997. This information is current as of 1:00 p.m. (CDT) on May 9, 1997.

Contact:

EDWARD SCHWEIBINZ (630)829-9712 MARK RING (630)829-9703 /

d l 9705120101 970509

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l PDR I&E l PNO-III-97-043 PDR l 1.200J3