ML19316A231
| ML19316A231 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/13/1976 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19316A225 | List: |
| References | |
| NUDOCS 7912030348 | |
| Download: ML19316A231 (4) | |
Text
_..
/
%g umismsvaras NUCLEAR REGULATORY COMMISSION f
wasmwovon.o.c. noses
{
.. j
\\,...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 1
SUPPORTING AMENDMENT NO. 33 TO FACILITY LICENSE NO. DPR-38 AMENDMENT NO. 33 TO FACILITY LICENSE NO. DPR-47 A!ENDMENT NO. 30 TO FACILITY LICENSE NO. DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1, 2 AND 3 DOCKETS NOS. 50-269, 50-270 AND 50-287 Introduction _
During the summer of 1973, inspections at two reactor facilities revealed a high incidence of inoperable hydraulic shock suppressors (snubbers) l As a result manufactured by Bergen Paterson Pipesupport Corporation.
of those findings, the Office of Inspection and Enforcement required each operating reactor licensee to imediately inspect all Bergen
)
Paterson snubbers utilized on safety systems and to reinspect them 45 to 90 days after the initial inspection. Snubbers supplied by other manufacturers were to be inspected on a lower priority basis.
The majority of suppressor failures were detemined to be caused by the degradation of. seal material due to incompatibility with the operating environment and the resultant laakage of hydraulic fluid. Although a seal replacement program has reduced the incidence of failure, problems Our review of the snubber have continued due to mechanical defects.
experience at ' reactor facilities has therefore shown the need for technical specifications requiring snubber operability and surveillance. By letter dated June 30, 1975, we requested that the licensee submit an application to change the Oconee Technical Specifications to be in confomance with sample technical specifications provided. By letter dated December 18, i
1975, we advised the licensee of changes to the sample technical specifications. The licensee responded by letters dated August 15, 1975 February 19, and June 22, 1976. During our review of the proposed These changes, we fouhd that certain modifications were necessary.
modifications were discussed with the licensee and have been incorporated into the proposed Technical Specifications.
l
.g 9
Y9120303pf
~
e o
' Evaluation _
Snubbers are designed to prevent unrestrained pipe motion under dy loads as might occur during an earthquake or severe transient while allowing normal thermal movement during startup and shutdown.
The consequence of an inoperable snubber is an increase in the prob of structural damage to piping resulting from a seismic or other It is, therefore, postulated event which initiates dynamic loads.
necessary that snubbers installed to protect safe l
to assure their opeaability.
Examination of Mactive snubbers at reactor facilities has s the high incidence of failures observed in the suniner of 1973 was caused by severe degradation of seal materials and subsequent leakag The basic seal materials used in Bergen Paterson the hydraulic fluid. snubbers were two types of polyurethane; a millable gum Material tests containing plasticizers and an unadulterated molded type.
perfonned at several laboratories (Reference 1) established that the millable gum polyurethane deteriorated rapidly under the temperature Although and moisture conditions present in many snubber locatio it also may be unsuitable for application in the higher tempe environments.
upper temperature limit for the molded polyurethane.
compounds, which should give satisfactory perf severe conditions expected in reactor installations.
j
- An extensive seal replacement program has been carried out
-j Although the reactor facilities.
very good with no serious degradation reported thus far.
These failures have snubber failures, some failures continue to occur.
generally been attributed to faulty snubber assembly and installation The loose fittings and connections and excessive pipe vibr Because of the limited to units manufactured by Bergen Paterson.
continued incidence of snubber failures, we have concluded that snubb operability and surveillance requirements should be incorporated into We have further concluded that these requirements should be appited to all safety related snubbers, reg the Technical Specifications.
i of manufacturer, in all light water cooled reactor facilities.
/
Report H. R, Erickson, Bergen Paterson to K. R. Goller, NRC,
)
N Hydraulic Shock Sway Arrestors
.0ctober 7 -1974,'Subjecti 4
.a
1
(
4 l d Bases to We have developed the attached Technical Specifications an bber performance provide additional assurance of satisfactory snuThe specificatio and reliability.during reactor operation and prior to startup.
a period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is
- is required only during low probability events, all its before the reactor or replacement of a failed snubber expeditiously.of must be shut down.
ther safety-related equipment and provides for remedial action toFailure of a pipe, piping sys ilure of a single with 10 CFR 50.36(c)(2).
component would not necessarily result from the fa id of hydraulic snubber to operate as designed, and even a snubber devo d reduce pipe fluid would provide support for the pipe or compone t
>ccurring during the time allowed for repairConsidering th ubber motion.
units, repair or replacement in a shorter time per o listic period small.
1 for remedial action to be taken.
j nce An inspection program is specified to provide additional assu j
i i
Thus the l
that the snubbers remain operable.
upon maintaining a constant level of snubber protect on.the obs required inspection interval varies inversely withThe lon i l i
Specifications after a record of no snubber failuresExperience failures.
is nominally 18 months.
that the required surveillance program should pro il are compatible with the operating environment.
has not been demonstrated to be compatible with the operail the are required to be inspected every 31 days untes ltd h Technical To further increase the level of snubber reliability, t e ling cycle. The Specifications require functional tests once each refue d bleed.
tests will verify proper piston movement, lock up an Teci.nical Sp We have concluded that the proposed additions to thef l snubbe as modified, increase the probability of success t ble.
~
W
~
s.
Environmental Consideration We have determined that these amendments do not au Having made this not result in any significant environmental impact.
determination, we have further concluded that these amendments involve an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR BS1.5(d)(4) that an environment &1 statem i
mental appraisal need not be prepared in i
. negative declaration, or env ron connection with the issuance of these amendments.
=
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards censideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulat or to the health and safety of the public.
DATE:
October 13, 1976 8
e
- - -,