ML20098E588
| ML20098E588 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 09/20/1984 |
| From: | Kuncl L, Kunel L NEBRASKA PUBLIC POWER DISTRICT |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-84-03, IEB-84-3, NLS8400020, NUDOCS 8410010097 | |
| Download: ML20098E588 (9) | |
Text
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Nebraska Public Power District
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S NLS8400020 September 20, 1984 Mr. John T. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011
Subject:
NPPD Response to IE Bulletin 84-03, " Refueling Cavity Water Seal" Reference 1:
U. S. Nuclear Regulatory Commission IE Bulletin 84-03 Dated August 24, 1984, " Refueling Cavity Water Seala
Dear Mr Collins:
Reference 1 requested that NPPD evaluate the potential for and consequences of a refueling cavity water seal failure and provide a summary report of these actions.
Specific areas of concern and consideration are as follows:
1.
Gross seal failure.
2.
Maximum leak rate due to failure of active components such as inflated seal.
3.
Make-up capacity.
4.
Time to cladding damage without operator action.
5.
Potential effect on stored fuel and fuel in transfer.
6.
Emergency operating procedures.
A summary report for each of the areas of concern is given below:
1.
Gross Seal Failure The refueling bellows forms a seal between the reactor vessel and the surrounding primary containment drywell to
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Mr. John T. Collins Paga 2 September 20,-1984 permit. flooding of the space (reactor well) above the vessel during refueling, operations.
The refueling ' bellows assembly (see Attachment "A") consists of a stainless steel
. bellows, a backing plate, a self-energizing spring seal, and a removable guard ring.
The backing plate surrounds the outer circumference of the bellows. to protect it and is equipped with a tap for testing and for monitoring leakage.
The self-energizing spring seal is located in the area between the bellows and the backing plate and is designed to limit water loss in. the event of_ a bellows rupture by yielding to form a seal against the backing plate.
The guard ring attaches to the assembly and protects the inner circumference of the bellows.
The guard - ring can be removed from above to inspect the bellows.
The assembly is welded to the reactor bellows support skirt and the reactor well seal bulkhead plate.
The reactor refueling bellows-assembly is welded to the reactor vessel shell flange (see Attachment "B") and the reactor well seal bulkhead plate.
The bulkhead plate is welded to the primary containment drywell wall.'
-Due to the passive design of the wetor well bellows seal, gross seal failure is considered..to tu a remote possibility.
However, in the event that gross seel failure did occur, the backup, self-energizing spring seal would significantly limit the amount of seal leakage.
As a precautionary measure, seal leakage is monitored locally once per shift by station operators.
In addition, seal leakage in excess of five gallons per minute will annunciate an alarm in the control room.
'2.
Maximum Leak Rate Due to Failure of Active Components Such as Inflated Seal As stated above, the design does not incorporate any active seal components.
3.
Make-Up Capacity Gross make-up capacity for the refueling cavity can originate from two sources, Core Spray (CS) and Reactor Heat Removal (RHR).
Two Core Spray pumps can supply 4720 gpm each, while four RHR pumps can supply 7700 gpm each.
Both systems have redundant sources of water, L
either from the condensate storage' tank or from the suppression pool.
The spent fuel pool normal make-up supply is from the Reactor Building auxiliary condensate pump with a flow of 275 gpm.
-4.
Time to Cladding Damage' Without Operator Action Due to station design, the only time fuel would be uncovered would be if it was in transit at the time of 4
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- Paga 3 September 20, 1984 bellows failure. _And, since it is anticipated that the refueling cavity water level can be restored and maintained through the Core Spray and/or ti.e Reactor Heat Removal systems, ample time would exist to place such fuel in a safe
-location (either into the reactor vessel or the spent fuel pool), as described below.
The exact time to cladding damage without operator action would require a significant amount of analysis by the NSSS vendor, General Electric.
Due to the passive nature of the_ bellows-seal, and the remote possibility of gross seal failure, the District does not believe that such an evaluation is warranted.
5.
Potential Effect On Stored Fuel and Fuel In Transfer In the event of gross seal failure and loss of water level in the refueling cavity with the fuel pool gate removed, a minimum of 2 feet of water would remain over the spent fuel located in the fuel pool.
In the event of refueling floor high radiation as a result of the low fuel pool level, Emergency Operating Procedure 5.3.5 would be implemented as described in paragraph 6 below.
If the decreasing refueling cavity water level was detected while fuel was being transferred, the common action taken by Operations would be to return the fuel to the reactor vessel or fuel pool, whichever is more expedient.
6.
Emergency Operating Procedures
' Emergency Operating Procedure 5.3.5,
" Refueling Floor High Radiation", provides instructions to Operations personnel as to required actions to take in the event of a refueling accident.
Actions to take in the event of a problem with reactor cavity water level are addressed therein.
It is the judgement of the District that the stainless steel, passive refueling cavity seal design at Cooper Nuclear Station would fail in a manner such that only minor leakage would occur and that a gross seal failure would not occur.
Should you have any questions on this response, please contact me.
I f
.L. G.
uncl Assistant General Manager-Nuclear LGK:emz20/8 1
Attachments cc:
S. Nuclear Regulatory Commission
- Attention: Document Control Desk Washington, D.C.
20555-
Mr. John T. Collins Pcg3 4 September 20, 1984 STATE OF NEBRASKA)
)ss PLATTE COUNTY
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L. G. Kuncl, being first duly sworn, deposes and says that he is an authorized representative of the Nebraska Public Power District, a public corporation and political subdivision of the State of Nebraska; thtt he is duly authorized to submit this information i
on behalf of Nebraska Public Power Dintrict; and that the statements contained herein are true to the best of his knowledge and belief.
LL G. Kuncl sworn to before me this N day Subscri sence an I
NOTARY PUBLIC l
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