PNO-IV-89-052B, on 890823,unplanned Reactor Shutdown Due to Inoperable Control Rod.Licensee Plans to Remove Control Rod Pair W/Bldg Crane in Unshielded Configuration to Shielded, Contained Evolution

PNO-IV-89-052B:on 890823,unplanned Reactor Shutdown Due to Inoperable Control Rod.Licensee Plans to Remove Control Rod Pair W/Bldg Crane in Unshielded Configuration to Shielded, Contained Evolution

ML20246F718
Person / Time
Site:	Fort Saint Vrain
Issue date:	08/23/1989
From:	Westerman T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-89-052B, PNO-IV-89-52B, NUDOCS 8908310116
Download: ML20246F718 (2)

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August 23, 1989 ,

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' PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-IV-89-89-52B i

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j b This preliminary . notification constitutes EARLY notice of events of POSSIBLE {

P safety or public interest significance. The information is as initially received l F without verification or evaluation, and is basically all that is known by the Region IV: staff on this date.

FACILITY: Public Service Company of Colorado Licensee Emergency Classification:

Fort St. Vrain Notification of Unusual Event i Docket: 50-267 Alert E Site Area Emergency General Emergency i

X Not Applicable I

SUBJECT:

UPDATE OF UNPLANNED REACTOR SHUTDOWN DUE TO INOPERABLE CONTROL R0D

' This is a further update to the preliminary notification' issued on August 18, 1989, and updated on August 21, 1989. The licensee has~ modified his initial plan to remove the. control rod pair with the building crane in an unshielded configuration to a shielded, contained evolution.

At 8 a.m.-MDT,: August 23, 1989, the reactor vessel had been depressurized to atmospheric. In preparation for removing the control rod, the assembly was lifted to a support stand approximately 2 feet above the top of the reacter vessel. Access ports on the side of the drive mechanism were removed and the cable mechanism inspected. No frayed cable was evident. The licensee's inspection indicated that one absorber' string is not moving freely and appears

'to be mechanically bound down below the upper mechanism. The highest measured radiation levels were reported to be 40 MR/hr inside the control rod assembly.

~The cable was clamped and removed from the drum for each of the two absorber strings. The cable was then brought out through the top of the control rod drive mechanism and new cable spliced to the old cable. Attempts to pull the absorber strings confirmed that one string moves freely at about 200 pounds force and the other appears to be mechanically bound. (Moves out at about 900 pounds force).

An absorber string weighs approximately 120 pounds.

The control rod assembly is to be replaced into the reactor vessel and the licensee will attempt to withdraw the absorber sections into the control rod guide tubes using the spliced cables. If this evolution is successfully completed, the control rod removal and replacement will be completed using the auxiliary transfer cask and normal refueling procedures.

The retroyed control rod assembly will be inspected in the licensee's hot service facility. The licensee will meet with the NRC staff to discuss the apparent cause of the control rod failure prior to any attempt to restart.

. Additional regional personnel are assisting the resident inspectors in observing 4 the licensee's actions. $

This information has been confirmed with a licensee representative.

T CONTACT: T. Westerman, FTS 728-8145 (

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