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


                              UNITED STATES 
                         ATOMIC ENERGY COMMISSION 
                         WASHINGTON, D.C. 20545  

                                MAR 22 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 #74-4 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. 

                                   Harold D. Thornburg, Chief  
                                   Field Support & Enforcement Branch 
                                   Directorate of Regulatory Operations 

As stated 

cc:  D. F. Knuth, RO 
     J. G. Davis, RO 
     B. H. Grier, RO 
     A. Giambusso, RO 
     J. Hendrie, L 
     D. J. Skovholt, L 
     Brodsky, Naval Reactors 

 To All BWR Facilities                                 Date 3/22/74 
     With a Current Construction Permit                DRO Bulletin  #74-4 


The enclosed DRO Bulletin #74-4 "Malfunction of Target Rock Safety Relief 
Valves" has been sent for completion of the requested action to all 
utilities presently licensed to operate a BWR generating plant. 

This Bulletin is being sent to you as general information and requires no 
responsive action on your part. 



DRO Bulletin #74-4 

To All BWR Facilities with Current                         Date 3/22/74 
     Operating Licenses                                DRO Bulletin #74-4\ 


The enclosed DRO Bulletin #74-4 "Malfunction of Target Rock Safety Relief 
Valves" is sent to provide you with information reported by Tennessee Valley
Authority as an abnormal occurrence at the Brown's Ferry Unit 1 reactor 

This information may have applicability at your facility(ies). Action 
requested on your part is identified in Section B of the enclosed Bulletin. 



Enclosure: DRO Bulletin #74-4 


We have reviewed information from the Tennessee Valley Authority describing 
the malfunction of a Target Rock (TR) safety relief valve at Browns Ferry 
Unit 1. As a result of this malfunction, the second stage piston of the 
valve was prevented from reseating after actuation, resulting in the primary 
system being blown down,to 20 psig before the spring on the assembly could 
reseat the piston. 

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 piston 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. 

     3.   A pin was inserted in the hole and the hole peaned 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 values. 

B.   Action Requested 

     1.   It is requested that during your next outage you complete the 
          recommended modifications to the second stage piston stem locking 

     2.   It is requested that you ascertain what other modifications to the
          original design have been made or recommended for the Target Rock 
          valves now installed in your facility and describe the action you 
          have taken or will take to complete such modifications. 

     3.   Please inform this office within 20 days of your receipt of this 
          a.   Of your plans to complete the modifications to second stage 
               piston stem locking nut; and 

          b.   Of the action you have taken or will take to complete other 
               modifications recommended for the Target Rock valves now 
               installed in your facility. 

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