ML20100C260
| ML20100C260 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/26/1984 |
| From: | Lempges J NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| IEB-84-03, IEB-84-3, NMP-9920, NUDOCS 8412050372 | |
| Download: ML20100C260 (2) | |
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A 31 NMP-9920-NIAGARA MOHAWK POWER CORPORATION NIAGARA MOHAWK-300 EMIE BOULEVARD. WEST SYRACUSE. N. Y,13 202 November 26, 1984 United States Nuclear Regulatory _ Commission.
Office of Inspection and Enforcement Washington, DC 20555 Re: Docket No. 50-220 IE Bulletin #8h-03 Gentlemen:
J IE Bulletin 8h-03 requires that an evaluation be performed addressing
.the refueling cavity water seal failure experienced at Haddam Neck. The failure resulted in the complete drainage of the refueling cavity into the
.dryvell.
The water seal at Nine Mile Point Unit #1 between the refueling, cavity and the dryvell is provided by the refueling seal platform, dryvell refueling seal bellows, and reactor expansion bellows. The reactor expansion bellows is a cylindrical one piece stainless steel bellows seal. Both sides are velded connections, one side is velded to the reactor vessel, and the other to the refueling seal platform. The refueling seal platform is a welded two piece cylindrical flat plate fixed to.the inside-of the dryvell. It contains 2h openings of which 6 are ventilation duct hatches. All 24 openings are open when the reactor cavity is drained, and are sealed with cover plates when the cavity is flooded. The cover plates are bolted in place with a gasket seal between the cover plates and the reactor seal _ platform. These sealed openings are inspected for leakage as soon as water starts flooding
,the_ reactor head' cavity (per procedure N1-0P-34). The dryvell refueling seal bellows is also a cylindrical one piece stainless 'ateel bellows seal,
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and is velded to the exterior dryvell shell, and the refueling cavity lining.
The reactor expansion bellows is monitored by a nonindicating flow switch circuit which alarms in the Control Room on a high flow reading.
The refueling cavity water seal at Nine Mile Point Unit #1 could not ex-perience a failure similar to that which occurred at Haddam Neck. The seal
. construction provides steel boundaries which are either velded or bolted in place. Therefore, a failure due to lack of interference between the seal annulus width and the opening could not occur at Nine Mile Point Unit #1.
'For a gross failure to occur it would require a structural failure of a welded' connection, which would be highly unlikely.
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-Page'.-IE Bulletin 84-03
- November :26, ~ 1984 :
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e The spent fuel pool is designed such that should it be inadvertently edrained.to its: lowest penetration the. fuel would-still.be covered by
-approximatfly'one foot of water. It is possible however, for a fuel bundle
-in transit between the reactor core and the spent fuel storage pool to become
-uncovered. 'However, it is'a simple. operation for the-operator to lower the bundle"to a position where_it would~ remain covered. Assuming no operator actions the consequences of uncovering a newly discharged fuel bundle would.
be_high radiation levels.at the refueling floor, and possible release of-radioactivity into the secondary containment...Eeferencing NUREG/CR-0649-n(Spent Fuel Heatup Following-Loss of Water During-Storage),-. assuming-a 30 day; minimum decay time and no ventilation, a peak clad temperature of 750*C
'vould occur after 2h hours, which would not be an adequate' temperature for
! cladding failure to occur.
Condensate transfer is automatically initiated to provide makeup for the
- spent fuel' pool on a lov level alarm. Operating procedures also.specify' instructions for correcting alarm. conditions.
'Therefore it has been determined that for'Nine Mile Point Unit #1 the poss-ibility of a gross head cavity water seal failure is highly unlikely, and there are no plans for any additional actions.
Very truly yours, y,n Thomas E. Lempges Vice President Nuclear Generation TEL/lo
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