ML20127G389
| ML20127G389 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/15/1974 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wachter L NORTHERN STATES POWER CO. |
| References | |
| IEB-74-14, NUDOCS 9211160577 | |
| Download: ML20127G389 (1) | |
Text
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ATOMIC ENERGY COMMISSION 1
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OIRECTOR ATE Or REGULATORY OPER ATIONS J
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NOV i 5 3974 Northern States Power Company Dockst No. 50-263 ATrW: Mr. Lee Weehter Vice President Power Producties and system operatism 414 Nicollet Mall Minneapolis, Mianosota
$4441 Centlement The enclosed RO Du11stia requests actions by you with regard to your boiling water reactor (BWR) facility with operating license.
Should you have questions regarding this Bulletin or actions requested of you, please coat act this office.
Sfacerely, James G. Kappler Regional Director Enclosuret to Du11stia 74-14 bec:
Central Files RO Files PDR Local PDR 5
OGC Beth, P-506A A. Rosiman This request for generic information was approved by GAO under a blanket clearance number B-180225 (R0072); this clearaace expires July 31, 1977.
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9211160577 741115 PDR ADOCK 05000263 G
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November 15, 1974 R0 Bulletin 74-14 BWR REL1EF VALVE DISCRARGE TO SUPPRESSION POOL 5
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Description of Circumstances:
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_Various BWR 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-4 charge steam is quenched.
With the suppression pool water at its i
normal temperature, the steam quenching proceeds in the. expected manner.
Extended'dischargelof a single relief valve, however, may1 j-raise the local temperature of the receiving' water to a level at which l
the steam _ quenching becomes erratic and local pressure pulses of-signi-ficant magnitude may be generated.
y Past occurrences at several AEC licensed' reactors have resulted in j
varying degrees of darage, such as baffle displacement and piping 1
support damage. This damage has previously been attributed to a j
variety of causes; however, ' based upon more recent evaluations by the nuclear steam system supplier, General Electric Company,-damage may l
have resulted from local pressure pulses as described above.
Since i
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 i
in the reactor coolant system, without sufficient attention to the-l-
effects of extended steam discharge on the pressure suppression pool structure. This situation is currently;under review by the Regulatory i
staff including consideration of whether revision to. technical-specifi-
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cations may be required.
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Action Requested of Licensees:
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Review your current operating procedures which are applicable to j
the situation discussed above, to determine _ whether they are
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adequate or_should be modified'in any of the following: areas:
-a.
Limiting bulk _ suppression pool cemperatures during normal-j:
operation and during'controllabic transients.
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Pequiring 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 rescat properly.
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.
In cases of relief valve discharge, promptly initiating suppression pool circulation to dissipate local peaking of water temperatures.
c.
Conduct of visual internal and external inspection of sup-pression pool structure for evidence of damage in instances where one or more relief valve (s) fails to reteat properly or discharges to the suppression pool for an extended period of time.
During this review, the various aspects of plant operations should be considered so that procedural changes designed to minimize the effect of steam discharge to the suppression pool do not have an adverse effect in other areas.
2.
Report to this office in writing within 20 days of receipt of this Bulletin the results of your procedural review and any changes you have made or plan to make in your operating procedures, including the date when such changes were or will be completed.
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