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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