Bulletin 74-004A: Malfunction of Target Rock Safety Relief Valves


                              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 


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 

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 


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. 



DRO Bulletin #74-4A 

 TO ALL BWR Facilities                            Date 
With A Current Construction Permit                DRO Bulletin #74-4A 


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. 



DRO Bulletin #74-4A 


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 

     As a corrective measure, all the TR valves on Unit 1 were replaced with
     valves from Unit 2 after the following modifications had been 

     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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