ML17054D292
| ML17054D292 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 11/15/1974 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| References | |
| IEB-74-14, NUDOCS 8010150702 | |
| Download: ML17054D292 (6) | |
Text
0 Directorate of Regulatory OperationsBulletin 74-14 November 14, 1974 BVR RELIEF VALVE DISCHARGE TO SUPPRESSION POOL Descri tion of Circumstances Various BHR licensees have in the recent past, experienced unplanned actuation of reactor coolant system steam relief valves.
These valves typically discharge to the suppression pool, where the dis-charge steam is quenched.
LG.th the suppression pool water at its normal temperature, the steam quenching proceeds in the expected manner.
Extended discharge of a single relief valve, however, may raise the local temperature of the receiving water to a level at which the steam quenching becomes erratic and local pressure pulses of signi-ficant magnitude may be generated.
Past occurrences at several AEC licensed reactors have resulted in varying degrees of damage, such as baffle displacement and piping support damage.
This damage has previously been attributed to a
'variety of causes;
- however, based upon more recent evaluations by the nuclear steam system supplier, General Electric Company, damage may have resulted from local pressure pulses as described above.
Since only a limited number of temperature sensors are provided within the suppression pool, local temperature increases and resulting pressure pulses have not been specifically identified in past occurrences.
It appears that, during events in which relief valves cannot be closed promptly, primary attention by the operator may be directed under current procedures toward minimizing temperature and pressure transients in the reactor coolant system, without sufficient attention to the effects of extended steam discharge on the pressure suppression pool structure.
This situation is currently under review by the Regulatory staff including consideration of whether revision to technical specifi-cations may be required.
Action Re uested of Licensees 1.
Review your current operating procedures which are applicable to the situation discussed above, to determine whether they are adequate or should be modified in any of the following areas:
R0+~ulletin 74-14 a.
Limitin bulk su g
ppression pool temperatures during normal operation and during controllable transients, b.
Requiring reactor trip if the bulk suppression pool tempera-ture exceeds that established as a limit for controllable transients or if relief valve(s) fails to reseat properly.
In cases of relief valve discharge, promptly initiating suppression pool circulation to dissipate local peakin of water temperatures.
p e
oca pea ng of c.
Taking prompt steps in case of inadvertent relief valve actuation or failure to reseat, to minimize the duration of steam discharge to the suppression pool.
d.
e.
Conduct of visual internal and external inspection of sup-pression pool structure for evidence f d o
amage n ins tances where one or more relief valve(s) fails to reseat ro r
or dischar e to the s
o reseat properly ge o t e suppression pool for an extended period of time.
During this review t be considered w, the various aspects of plant operati h
ld ons s
ou effect of so that procedural changes designed to i i i h
P steam discharge to the suppression pool do not have an adverse effect in other areas.
2.
Re Report to this office in writing within 20 da s of recei Bulletin the results of our n
ays o
receipt of this have made or lan to m
s o
your procedural review and any chanpes you p
to make in your operating procedures, including the date when such changes were or will be completed.
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UNITED STATES ATOMIC ENERGY COMMISSION OIRKCTORATK OF RKOUI ATORY OPKRATIONS RKOION I 631 PARK AVENUE KING OF PRUSSIA, PENNSYLVANIA 19406 Niagara Mohawk Power Corporation Attention:
R. R. Schneider Vice President, Electx'ic Operations 300 Erie Boulevard Vest
- Syracuse, NY 13202 October 25, 1974 Docket No:
50-220 Gentlemen:
The enclosed RO Bulletin requests actions by you with regard to your reactor facility(ies) with operating license or construction permit.
N Should you have questions regaxding this Bulletin or actions requested of you, please contact this office.
Sincerely, Wc James P.
eilly Director
Enclosure:
cc:
P. A. Burt, General Superintendent, Nuclear Generation T. J. Perkins, Plant Superintendent C. L. Stuart, Assistant Plant Superintendent E. B. Thomas, Jr., Esquire A. Z. Roisman, Counsel for Citizens Committee for Protection of the Environment