ML20100D752
| ML20100D752 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 11/27/1984 |
| From: | Edelman M CLEVELAND ELECTRIC ILLUMINATING CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-84-03, IEB-84-3, PY-CEI-OIE-0019, PY-CEI-OIE-19, NUDOCS 8412060041 | |
| Download: ML20100D752 (7) | |
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THE CLEVELAND ELECTRIC ILLUMIN ATING COMPANY P.O. box 5000 - CLEVELANo oHlo 44101 - TELEPHONE (216) 622-9800 - lLLUMINATING BLDG. ~ 55 PUBLICSoVAFIE Serving The Best Location in the Nation MURRAY R. EDELMAN November 27, 1984 vicE PRESloENT PY-CEI/01E-0019 L NUCLEAR Mr. James G. Keppler, Regional Administrator U. S. Nuclear Regulatory Commission, Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137 Perry Nuclear Power Plant Docket Nos. 50-440; 50-441 IE Bulletin 84-03 Refueling Cavity Water Seal
Dear Mr. Keppler:
In accordance with the request in I.E. Bulletin 84-03, " Refueling Cavity Water Seal," the attached summary report is provided to address the potential for, and consequences of, a refueling cavity water seal failure.
The evaluation includes consideration of each of the items noted in the Bulletin, and concludes that this is not a concern at the Perry Nuclear Power Plant (PNPP) due to the type of cavity water seal utilized in the design of PNPP.
Kerytruyyurs,
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Murr R. Edelman Vice President Nuclear Group MRE:njc Attachment cc: Jay Silberg, Esq.
O John Stefano a
J. Grobe U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Washington, DC 20555 U.S. Nuclear Regulatory Commission c/o Document Control Desk Washington, DC 20555 NOV 301984
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' Summary Report on Refueling Cavity Water Seal Failure In Response to I.E. Bulletin 84-03~
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' This summary report addresses each;of the-items-noted.in'the I.E. Bulletin "84-03,1which requests evaluation ofcthe potential for, and consequences of, failure of the refueling cavity-water seals. ~.The evaluation considers (1) gross sealifailure (2) maximum leak rate due to failure of active components such'as' inflated seals (3) make-up capacity (4) time.to cladding damage without operator action (5) potential effect on stored fuel and fuel in transfer
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- and (6) emergency operating procedures.
2 ( 1).1
- Gross-Seal Failure.
Th'e' design of' Perry' Nuclear. Power Plant (PNPP) does not utilize pneumatic meals 'for the _. refueling cavity water seal, - but rather uses a -
' metal bellows' design manufactured by Pathway Bellows Co.
All connections are welded.. The metal bellows provide a flexible watertight seal-between the reactor preesure vessel.and the drywell structure. The fdesign includes a~self-energizing stainless sNeel spring which functions as a secondary sealt to limit.waterzlocs following a rupture in the main
-bellows element. A half coupling is provided?on the backing plate for-
- monitoring leakage. Figure 1 illustrates the seal design.
The leak rate would be very small in case of a gross failure of the primary bellows -element -because of the secondary seal.
.(2).
Maximum Leakage Rate Due To Failures Of Active Components Such As Inflated Seals.
The. design at PNPP does not incorporate any active components. Leakage would be very small as indicated in (1) above.
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(3)..
Makeup Capacity Makeup to the upper-pools'is provided by the Fuel Pool Cooling and Cleanup system (G41). Normal makeup is 300 gallons per minute (gpe).
Maximum makeup of 3000 gpa.from she Fuel Pool Cooling and Cleanup SystemL is available by aligning all' flow to the upper pools.
(4). : Time To Cladding Damage Without Operator Action.
IfLbellows failure occura during operation of the reactor, the*e would
' be no loss of the primary coolant since there is no communication between the sealed primary coolant system and the upper containment pools. Thus there is no possibility of cladding damage to fuel residing in the reactor core.'
In fact, bellows failure will' result in no loss of
. water at all'if the drywell head seal is effective. See Figure No. 2.
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6-pg. 2 of 6 LIf bellows failure occurs during. refueling, with_the gate between the reactor welliand the steam. dryer' pool. removed, and the gate between the a,
. steam dryer pool and^ fuel. transfer canal removed, the water level:in the reactorLwill eventually drain down to the flange of'the. reactor vessel, but"onlyfif the coolant makeup water to the:reactorLwell and the steam
- dryer pool.has been cut off to reduce leakage through the failed seal.
> Because of 'the stainless steel secondary seal, catastrophic loss of: the
" water'in the upper pools is not possiblei The RHR system would; continue to maintain ths wcter level in the reactor'to the flange of the reactor ivessel-and continue to supply cooling to remove decay heat from the
. fuel.,Therefore, there is no possiblility of_ cladding damage to fuel 1
residing in the reactor core. See Figure No. 3.
_ Fuel in transit can be safely stored should a leak occur. As noted above, the' leak rate would be very small, and'the Fuel Pool Cooling and
. Cleanup System supplies 300 gallons per minute to the pools. This will allow for transit of the fuel to the upper containment storage pool or back to the reactot vessel.
The maximum number of-fuel assemblies which can be stored in the storage racks'in the containment pool is 190. Assuming that these. assemblies-are maximug power assemblies, then each would have a decay heat output-of 1.22x10 Btu /hr.,This value is 1.25 times the average heat output-of.
a-core discharge 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after shutdown and: assumes'a-burnup of the-
-fuel to 18,000 MWD /MT.
If.the upper containment pools were allowed to drain down because the
- Fuel Pool-Cooling and Cleanup system is shut off, and if the gate
- between the reactor well and the Steam Dryer Pool is not installed then the water level above the fuel assemblies stored in the containment ~
. storage racks would eventually fall to 5 feet. Because of the threshold step below the Steam Dryer Poolgate, 1.75 feet of this water would be in
.the Steam Dryer Pool and an additional 3.25 feet would be in the Fuel Transfer and Fuel Storage Pool.
-A total of 89,200 gallons of stagnant water would be available for cooling. Assuming this water is at 120"F, it would require 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to reach boiling. Thereafter the water would boil off at a rate of 2860 gal /hr. The water would boil to the top of the stored fuel assemblies 7
.after another 9 hourc.
The above is a worst case scenario. Cladding damage, based on this scenario,1would begin to occur approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after the water
-level drained down to the level indicated in Figure No.'3.
Since the PNPP refueling bellows incorporates a secondary seal, failed bellows
- leakage is expected to be negligible and drainage to the level indicated in Figure No. 3 is'not expected. Therefore, cladding damage without
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operator ' action is' not possible.
It should be noted also'that operation of the Fuel Fool Cooling and Cleanup' System or RHR System can keep the water level above the stored tfuel:and thus prevent fuel'eladding damage.
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pg. 3 of 6-(5)
Potential.Effect On Stored Fuel and Fuel In' Transfer.
See answer 'to (4) above.
f(6)
Emergency Operating Procedures.
-_If a failure of the bellows'should occur while the reactor is operating, it will not be possible to determine the failure since.the drywell head -
dcywell seal will prevent leakage from the upper containment pools.
.The failure will become apparent when.the reactor well is filled while
. preparing to refuel. Upon detection, the operator will need to assess
'whether or not the leakage has to be stopped. Leakage can be stopped by installing the reactor well-steam dryer pool gate and draining'the reactor well. Operation of the RHR System and Fuel Pool Cooling System
-will' assure that the fuel assemblies within the reactor core or fuel storage pool are covered with water and are being cooled.
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