ML20101A229
| ML20101A229 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 11/28/1984 |
| From: | Woolever E DUQUESNE LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 2NRC-4-197, IEB-84-03, IEB-84-3, NUDOCS 8412180278 | |
| Download: ML20101A229 (4) | |
Text
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$YL 2NRC-4-197 Telecopy Nuclear Construction Division November 28, 1984 Robinson Plaza. Building 2, Suite 210 Pittsburgh, PA 15205 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION:
Dr. Thomas E. Murley Administrator
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Response to IE Bulletin 84-03 Gentlemen:
This letter is forwarded in response to IE Bulletin 84-03, " Refueling Cavity Water Seal," dated August 24, 1984.
IE Bulletin 84-03 directed that CP holders provide an evaluation within 90 days of receipt of the bulletin.
The refueling cavity seal design for Beaver Valley Power Station Unit 2 (BVPS-2) does not use inflatible seals, as did Haddam Neck. The design of the BVPS-2 refueling cavity seal makes a gross failure extremely improbable.
The BVPS-2 abnormal refueling procedures, as noted in the att ached report, will be developed by July 1985.
The information provided by IE Bulletin 84-03, the BVPS-1 abnormal refueling procedures, and the attached report will be evaluated in the development of the BVPS-2 abnormal refueling procedures.
These procedures, upon completion and approval, will be made available, upon request, to either Region I or to the NRC Resident Inspector.
DUQUESNE LIGHT COMPANY By 3 s E. D. Woolever Vice President RW/wjs Attachment Mr. B. K. Singh, Project Manager (w/a) ec:
Mr. G. Walton, NRC Resident Inspector (w/a)
SUBSCRIBED AND SW TO B FORE ME THIS DAY OF o, 1984.
s Notary Public OhkO kffg8
~
' ANITA ELAINE REITER, NOTARY PUBLIC ROBINSON TOWNSHIP, ALLEGHENY COUNTY o
py MY COMMIS$10N EXPIRES OCTOCER 20,1986 I I M
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$ United Stcteo Nuciscr R2gulttery Cosmiccion Dr. Thom:0 E. Mur1sy Page 2 COMMONWEALTH OF PENNSYLVANIA )
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SS:
COUNTY OF ALLEGHENY
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On this j
day of
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, before me, a
-Notary'Public in and for said Commonwealth and County,' personally appeared E.
J. Wooleve r, who being duly sworn, deposed and said that (1) he is Vice President of Duquesne Light, (2) he is duly ' authorized to execute - and file
' the. foregoing Submittal on behalf of said Company, and - (3) the ' statements -
set forth in the Submittal are true and correct to the best of his knowledge.
Notary Public ANITA ELAINE REITER, NOTARY PUBLIC ROBINSON TOWNSHIP, ALLEGHENY COUNTY MY COMMISSION EXPlRES OCTOBER 20,1986
r ss-e ATTACHMENT Action to be taken by plants prior to' b'eginning refueling or within _90 days of receipt of this bulletin, whichever is sooner:
Evaluate the potential for and consequences of a refueling cavity water seal failure and provide a sunmaary report of these actions.
Such evaluations should include consideration of gross seal failure, maximum leak rate due. to failure of active components such as inflated seals, makeup capacity, time to cladding damage without operator action, potential ef fect on stored fuel and fuel in transfer and emergency operating procedures.
Response
Seal
Description:
The BVPS-2 refueling cavity water seal uses no inflatible seals. The seal is a stainless steel ring which spans the annular gap between the reactor vessel flange and the neutron shield wall / refueling cavity floor.
Double gaskets provide sealing near the inner and outer circumferences of the ring.
These four trapezoidal cross section gaskets are retained in two grooves in the seal ring by seg-mented steel retainers which are. screwed into the ring.
Alignment pins ensure proper - positioning of the ring.
Bolts around the outer c ircumference directly compress two outer gaskets, and, through tensioning arms, compress the two inner circumference gaskets.
As the reactor cavity is filled, the column of water above the seal ring provides additional force to ensure a tight sealing by the gaskets.
Gross Seal Failure The seal design, with retained trapezoidal gaskets, and the downward forces on the gasket ensure that the much smaller forces pushing the gaskets toward the gap will not push the gaskets into the gap.
The neoprene gasket material has no compressive: failure modes. Therefore, it is considered highly improbable that any failure of the BVPS-2 reactor cavity water seal could result in a gross leak similar.to that described in IE Bulletin 84-03.
Maximum Leak Rate due to Failure of Active Components such as Inflated Seals The BVPS-2 refueling cavity seal has no active component s such ' as inflated seals that may fail.
Makeup Capacity Several methods are available to provide makeup far in excess of any credible-leakage of the BVPS-2 seal design.
a) Charging /High Head Safety Injection Pumps - 550 gpm (runout) b) RWST Recirculation Pumps - 375 gpm (nominal) c) Low Head Safety Injection Pumps - 3000 to 5000 gpm (nominal and runout flows, respectively)
.a
-2 e
' Time to Cladding Damage without Operator Action Hand calculations were pe rformed to determine the time to cladding melt based on the following assumptions:
a) Fuel assembly is suspended in containment air b) Containment air temperature 105*
c) Initial temperature of fuel pool 140*
d) Decay heat load of 127.52 x 106 btu /hr at 150 hrs af ter shutdown The results of the hand calculations indicate a minimum of 60 minutes elapse before melting occurs with the assembly out of water.
Potential Effect on Stored Fuel In the event of reactor cavity seal failure, loss of water through the transfer tube would lower water levels in the spent fuel pool to elevation 742'1".
The stored spent fuel assemblies would remain covered by approximately 9 inches of water.
It has been calculated that it would take several hours for the water above the spent fuel to evaporate.
This calculation assumed that the postulated accident occurs after cycle 12 with an initial pool temperature of 140* and that no makeup water was added.
Before the water remaining above the stored fuel could evaporate completely, makeup water could be provided from the Refueling Water Storage Tank Recirculation Pumps, Primary Grade Water Pumps ' (no boron), or in extreme emergencies with the River Water or Fire Protection Systems' Pumps.
Design of the fuel racks would prevent criticality in the spent fuel pool under all conditions. In addition, the ventilation drains from the cooling unit return to the spent fuel pool.
Makeup to the RWST-is available through the CVCS System with 2000 ppm of borated water.
Potential Ef fect on Fuel in Transfer Fuel in the transfer tube or the spent fuel pool or fuel positioned horizontally in an upender would remain covered even in the event of a total failure of the' cavity water seal. The elevations would allow partial uncovering of the fuel if positioned in the Rod Control Cluster Change Fixture or vertically in the upender; however, this is not a credible event with the BVPS-2 water seal design.
Emergency Operating Procedures i.
As a result of this IE Bulletin, Abnormal Operating / Refueling Proce-dures will be developed to address decreasing refueling cavity water level and decreasing spent fuel pool water level.
These procedures will be developed and approved by July 1985.