ML20100A799
| ML20100A799 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 11/27/1984 |
| From: | Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | NRC OFFICE OF ADMINISTRATION (ADM) |
| References | |
| AEP:NRC:0898A, AEP:NRC:898A, IEB-84-03, IEB-84-3, NUDOCS 8412040091 | |
| Download: ML20100A799 (5) | |
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INDIANA & MICHIGAN ELECTRIC COMPANY 1
P.O. BOX 16631 COLUMBUS, OHIO 43216 l
November 27, 1984 AEP:NRC:0898A Donald C. Cook Nuclear Plant Unit Nos. 1 and 2 Docket Nos. 50-315 and 50-316 License Nos. DPR-58 and DPR-74 REFUELING CAVITY WATER SEAL (IE BULLETIE 84-03) s U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.0 20555 To Whom It May Concern:
This letter is in response to IE Bulletin No. 84-03, " Refueling Cavity Water Seal".
The following presents our review and conclusions of the likelihood and consequences of a refueling seal failure.
Gross Seal Failure The refueling cavity seal arrangement at the Donald C. Cook Nuclear Plant is a one piece seal inserted in a nominal two inch annular opening between the reactor vessel flange and the refueling cavity wall. This arrangement is different than that depicted in Figure 1 of HRC IE Bulletin 84-03 (Attachments 1, 2, and 3).
Inflation of the seal at normal pressure (15-30 psig) results in a slight downward force on the seal which tends to draw it into the annulus. Overpressurization would have a tendency to increase this downward force, but the rigid annulus configuration at Cook, end the rigidity of the seal rubber, prevent the 4 inch section of the seal from i
being pulled through the 2 inch annulus opening. In addition, the annulus configuration offers more surface contact with the cavity wall than the Haddam Neck design. In discussions with the Proscay Corporation, manufacturer of both the Cook and Haddam Neck refueling cavity seals, it was determined that the upper section of ';he Cook seal is wider than the type used at the Haddam Neck plant.
A130, the seal used at Cook has a greater rubber hardness, a 60 durometer, versus Haddam Necks 40 durometer, seal.
The Cook arrangement has been used during each refueling on both units since 1977, and at no time have there been' signs of seal failure.
Minor leakage has occurred; however, this has been controlled by increasing the seal inflation pressure, and by using a silicone rubber sealer (RTV).
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Mr. Jamer G. Ktpplsr AEP:NRC:0898A t
'Other utilities have also utilized single seal arrangements functionally identical to ours without experiencing any significant problems.- For example, Commonwealth Edison's Zion Plant has reported successful use of an inflatable. seal during several recent refuelings.
Of particular interest is the experience at TVA's Sequoyah Plant, where a Presray rubber seal is'used..in a 2 1/8 inch annulus. Conversations with TVA indicate that a test program using a segment of spare seal in an annulus mock-up demonstrated the adequacy of the passive portion of the seal.- The deflated segment of seal was tested up to a maximaan of
. 18.5 pai (1.5 times the normal' hydrastatic pressure of the refueling
= pool).
' Based on the-above review, we conclude that failure of.the active-seal component (i.e., the inflated lower portion of the rubber seal) will not result in a gross. seal failure or gross leakage because of the passive seal component (i.e., the solid wedge-shaped upper portion of-the rubber seal), and we believe the gross failure of the refueling cavity seal in a manner cited in IE Bulletin No. 84-03 to be highly improbable.
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Connannonces of Seal i maknaa
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I If the active portion of the refueling cavity seal were to fail, it is our belief, based on engineering judgement, that the passive portion of the seal would limit leakage to a value-less than the makeup 1
i' capacity, 4500 gallons per hour. Under such conditions, the operatore E
- would have several hours to start the makeup water (a relatively siuple operation) without danger of uncovering either the fuel in the vessel, the fuel in the spent fuel pool, or fuel that was in transit.
I-i Emergency Procedures
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In the event'that seal-leakage should occur, procedures are in-place for actions'to be taken. These procedures,are available at the P
site.
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A gross failure of the reactor cavity refueling seal is considered to be an unlikely event for the D. C. Cook Nuclear Plant because of the design of the seal. ~ Additionally, emergency procedures exist should.
seal leakage occur.
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Very truly y urs,
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Alejbch Vice President MPA/cm cc: John E. Dolan W. G. Smith, Jr. - Bridman R. C. Callen G. Bruchmann G.'Charnoff NRC Resident Inspector - Bridgman e
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