Bulletin 74-004A: Malfunction of Target Rock Safety Relief Valves
BL74004A UNITED STATES ATOMIC ENERGY COMMISSION WASHINGTON, D.C. 20545 MAY 1 1974 J. P. O'Reilly, Director of Region I N. C. Moseley, Director of Region II J. G. Keppler, Director of Region III E. M. Howard, Director of Region IV R. H. Engelken, Director of Region V RO BULLETIN #74-4A "MALFUNCTION OF TARGET ROCK SAFETY RELIEF VALVES" The enclosed Regulatory Operations Bulletin #74-4A is forwarded for dispatch to all BWR licensees with Operating Licenses for the requested action and to those licensees having a BWR Construction Permit for information only. The Region is to report to RO:HQ's when the licensee has responded to the Bulletin as well as when the licensee has informed the Region that the modifications have been completed. John G. Davis, Deputy Director for Field Operations Directorate of Regulatory Operations Enclosure: DRO Bulletin #74-4A cc: D. F. Knuth, RO J. G. Davis, RO B. H. Grier, RO A. Giambusso, L J. Hendrie, L A. Goller, L D. Skovholt, L . TO ALL BWR Facilities Date With Current Operating Licenses DRO Bulletin #74-4A Gentlemen: The enclosed supplement to RO Bulletin #74-4 "Malfunction of Target-Rock Safety Relief Valves" is sent to provide you with updated information on this problem. This supplement is identified as RO Bulletin #74-4A. This information may have applicability to your facility(ies). Action requested on your part is identified in Section B. of enclosed Bulletin. Sincerely, Director Enclosure: DRO Bulletin #74-4A . TO ALL BWR Facilities Date With A Current Construction Permit DRO Bulletin #74-4A Gentlemen: The enclosed supplement to RO Bulletin #74-4 "Malfunction of Target Rock Safety Relief Valves" is sent to provide you with updated information on this problem. This supplement is identified as RO Bulletin #74-4A. This supplement is being sent to you as general information and requires no responsive action on your part. Sincerely, Director Enclosure: DRO Bulletin #74-4A . MALFUNCTION OF TARGET ROCK SAFETY RELIEF VALVES We have reviewed with the responsible parties at General Electric Corporation in San Jose, their operating and testing experiences with the Target Rock Safety/Relief Valve, which prompted them to require the modification described in their FDI No. 138/78003 dated 2/28/74, for the safe operation, of BWR facilities. The failure of valves at their testing facility, in addition to those described in RO Bulletin No. 74-4 dated 3/26/74, suggests a generic weakness in the design of the second stage operator of the valve. General Electric and Target Rock are studying ways of modifying the second stage piston to permit maintenance as required without total replacement of the piston and disc, and to eliminate the present problem involving displacement of the locking device. Description of Circumstances A. The reactor was in the shutdown condition following reactor isolation as a result of high temperature in the main steam tunnel. During blowdown of the reactor following main steam line isolation valve closure, one of the pressure relief valves on the main steam header failed to reseat until pressure had been reduced to about 20 psig. The valve was subsequently removed and disassembled for inspection. It was found that the keeper over the locking nut on the second stage piston had worked loose and up to the stem over the securing wire. The movement of the keeper prevented the second stage pistion from reseating. As a corrective measure, all the TR valves on Unit 1 were replaced with valves from Unit 2 after the following modifications had been performed: 1. The tie wire and keeper were removed from the stem of the second stage piston. 2. A 1/16 inch diameter hole was drilled through the nut and the threaded portion of the stem. . - 2 - 3. A pin was inserted in the hole and the hole peened over so that the pin could not come out. This modification has been recommended by the Nuclear Steam System Supplier to all BWR's using the Target Rock valves. B. Action Requested: 1. We concur with the temporary fix described in the above referenced GE paper and request that the modification described in RO Bulletin #74-4 be made at the next cold shutdown at our facility. 2. Those facilities which have responded to Bulletin 74-4 that the interim fix will be made, need not respond to this bulletin. Those facilities which have not responded are required to do so within 20 days of receipt of this bulletin. 3. In the event the permanent modification is ready at the time of your next cold shutdown, it should be installed rather than making the temporary fix.
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