Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
BL74004
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
RO BULLETIN #74-4 "MALFUNCTION OF TARGET ROCK SAFETY RELIEF VALVES"
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
Enclosure:
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
Gentlemen:
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.
Sincerely,
Director
Enclosure:
DRO Bulletin #74-4
.
To All BWR Facilities with Current Date 3/22/74
Operating Licenses DRO Bulletin #74-4\
Gentlemen:
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
facility.
This information may have applicability at your facility(ies). Action
requested on your part is identified in Section B of the enclosed Bulletin.
Sincerely,
Director
Enclosure: DRO Bulletin #74-4
.
MALFUNCTION OF TARGET ROCK SAFETY RELIEF VALVES
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
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-
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
nut.
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
Bulletin:
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.