ML20029E638
| ML20029E638 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/13/1994 |
| From: | Lyster M COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MDL-LTR-94-0020, MDL-LTR-94-20, NUDOCS 9405190234 | |
| Download: ML20029E638 (5) | |
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Commonwealth Edison
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Drevien Nuclear Power Station 6500 North Dresden Road
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Morns. lHinois 60450 Telephone 815/942 2920 May 13, 1994 MDb LTR 94-0020 U.
S.
fluclear Regulatory Commission ATTN:
Document Control Deck Washington, D.C.
20555
Subject:
Dresden Nuclear Power Sta* ion Unit 1 Response to NRC Bulletin 94-01 NPC Docket No.50-010 Referencen (a)
NRC Bulletin 94-01, Potential Fuel Pool Draindown Caused by Inadequate Maintenance Practices at Dresden Unit 1,
dated April 14, 1994 (b)
M.
D.
Lyster letter to W.
L.
Axelson, transmitting Dresden Response to CAL RIII-94-001, dated March 3, 1594 (c)
NRC letter, " ORDER TO AUTHORIZE DECOMMISSIONING UF DRESDEN NUCLEliR PONER STATION, UNIT 1, AND AMENDMENT NO. 37 TO LICENSE NO, DPR-2",
Peter B.
Erickson (NRC) to D, L.
- Farrar, dated September 3, 1993.
The attachment to this letter provides the Dresden Station Unit 1 response t.o llRC Bulletin 94-01.
Dresden Station has taken a number of actions to ensure that all important systems related to the fuel storage pool are appropriately maintained and operated.
These actions have been discussed with the NRC staff on several occasions.
To the best of my knowledge and belief the statements contained in this document are true and correct.
In some respects these statements are not based on my personal knowledge, but on information furnished by other CECO employees, contractor employees, and/or consultants.
Such information has been reviewed in accordance with company practice, and I believe it to be reliable If you have any questions concerning this response, please contact
- n. Palagi, Unit 1 manager.
Sincereiy, N
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Michael D.
Lyster Site Vice President Dresden Station MDL/ulb
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Attachment:
Dresden 1 Response to NRCB 94-01
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B.
Martin, Regional Administrator - RIII S.
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Weiss - NRR j
P.
B.
Erickson, Dresden 1 Project Manager - URR
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D.
Pederson, Region III M.
N. Leach, Senici Resident Inspector, Dresden
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l ATTACHMENT 4
Dresden 1 Response to NRCB 94-01 BLTLLETIN RESPONSE i
The curveillances, testa, procedures and other actions described in this response are only applicable while fuel remains in the apent fuel pool (SFP) or opent fuel transfer pool.
Requented Action 1.
Verify that the utructures and ayatema required for containing, cooling, cleaning, level monitoring and makeup of water in the SFP are operable and adequate, conointent with the licensing bacia, to preclude high levels of radionucliden in the pool water and adverse effects on stored fuel, the SFP, fuel tranofer components, and related equipment.
Response to Requested Action 1.
a)
Containinq water in the SFP All structurca required for containing water in the SFP have been identified-and assecued to be operable and adequate.
This includes the concrete fuel pool, fuel transfer pool, transfer tunnel between the transfer pool and containment, and the steel vertical transfer tube with asacciated isolation valves. This concluaion is based on an inspection and engineering asseaament of the SFP and transfer tunnel, a general underwater ccmera observation of the transfer pool, and an ultrasonic examination of the fuel transfer tube and
.bypaso line.
Small, tight cracka have been observed in the pool walla and transfer tunnel.
These cracka are consistent with concrete of this age and design.
To ensure that water was not leaking from the pool, an evaporation rate study was performed on the fuel pool and transfer pool.
Based on the resulta of the study, all current water loan la within the boundslof the expected evaporation rate.
Dresden Station ia in the proccan of drilling and sampling groundwater monitoring wella in the immediate vicinity of the fuel atorage building to anaeca potential migration of water out of the spent fuel pool.
The water samplea are Leing evaluated for the presence of tritium, which has been determined to be the best isotopic indicator which can be directly correlated to fuel pool water.
The initial tritium cample results indicate low levels of communication between the opent fuel pool water and the immediate curroundings.
This level of communication la not algn: ticant relative to allowable effluent limits, and is consistent with the close match between the makeup rate and the expected evaporation rate.
After completing evaluation of l
the situation, Dreaden will incorporate campling of the wella into the routine Radiological Environmental Monitoring Program.
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,a Ultranonic examinationc of the 42" fuel trancfer tube and 8" bypass line were completed on February 16, 1994.
The results of this examination were described in Ref erence - (b), and it was concluded that these linen meet the original design requiremento.
As long as fuel remains in the fuel pool, Commonwealth Edicon plans to continue nampling *he new wella on the same quarterly frequency used for the current radiological environmental monitoring program.
tL 2n.ner of water in the SFP 2
The Dresden i spent fuel doca not generate aufficient heat to require cooling of the spent fuel water.
This fuel has been discharged for a number of yearn (last unit operation was October 31, 1978), and before 1983 ita decay heat had been reduced to the point where cooling was no longer necessary, g}
Cleanin't water in the SFP I
Ongoing fuel inspection aurveillances have established that the current water quality is not adversely affecting the fuel.
In addition, a fuel rack Jample examination by the Ceco Dyntem Materiala Analysin Department in 1990 concluded that the racka were atructurally cound.
The low rates of corrosion seen in j
Lhe cample evaluation have established that the current water quality is not significantly affecting the pool or its racks.
A temporary demineralizer was placed in cervice April 27, 1994.
This system is not designed to be operated continuously.
This demineralizer has significantly improved the water chemistry, thereby reducing the potential for corrosion.
The permanent fuel pool demineralizer system ia being designed to enable operation with the SFP gate installed between the SFP and the transfer pool and to preclude any niphoning potential.
The system is now scheduled to be operational by October 31, 1994.
d)
Monitoriner level of water in the SFP i
The Unit 1 fuel pool monitoring equipment which ensuren that water level la maintained at or above the Technical Specification limit is operable and adequate Both the storage pool and transfer pools have level gauges which are obnerved and recorded every shill.
An alarm in the Dresden Main Control Room in available to alert Operations of a storage pool low level condition.
This alarm io periodically calibrated, g)
Make-up of water in the SFP Routine make-up water to both pools la via either a clean demin or a contaminated demin hose station. This method is sufficient for the amounts required to make-up the evaporation lonces. Large capacity make-up is also available through either the contaminated domineralizer system that feeds both pooln or the fire protection hone station in the Spent Fuel Building.
The contaminated demin syntem can be used for large make-up.
The fire protection hose will be available when the contaminated demin system is not in service.
The contaminated domineralizer system is presently out of service for line
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Requested Action 2.
Ensure that systems for essential area heating and ventilation are adequate and appropriately maintained so that potential freezing failures that could cauce loss of SFP water inventory are precluded.
Responce to Requested Action 2.
Only two areas / lines are considered necessary to be heated while fuel is in the Unit t fuel pool or transfer pool: the fuel storage building (FSB), and
.l the 502' elevation transfer tube and bypass lines inside the containment building.
The FSB is permanently heated and maintained.
Any loss of heat would be discovered and remedied far sooner than the time it would take to j
nignificantly cool the pool water.
The *SB ventilation system is independent of the heating system, and therefore io not required for maintaining heat in the fuel storage building.
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1 Subatantial interim heating measures have been taken as described in Reference (b) to ensure that heating was provided to the 502' elevation transfer tube area inside containment.
Dreaden Station is currently evaluating options for long-term freezing protection of the transfer tube inside containment.
Dresden Station will continue to provide primary and back-up heat to the fuel transfer tube isolation and bypasa valves area during the heating cennon as described in Reference (b) while ultimate resolution of the long-term heating is being obtained.
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Requested Action 3.
Ensure that piping or hoses in or attached to the SFP cannot serve ao siphon or drainage paths in the event of piping or hose degradation or failure or the miopositioning of syatem valves, Response to Requented Action 3.
As discuaned below, Dresden Station has addreased the potential for alphoning and drainage of the SFP and spent fuel transfer pool and has determined that there in no significant potential for lowering the water levela below the i
Technical Specification limit:
1)
All hoses which run to the SFP and transfer pool are installed in a manner such that they can not siphon or drain the pool and transfer pool significantly.
2)
Spent Fuel Pool Cooling and Filter System:
The apent fuel cooling and filter system lines have been icolated from the spent fuel pool by closing the valve closeat to the pool and placing it out of nervice.
A siphon break has been installed on the one line to the cooling and filter system which doea not have an isolation valve.
Pe rmanent siphor. breaks for this system to supplement the isolation valves have been designed and will be inutalled by October 31, 1994.
(L MDL94m070 94)
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3)
Contaminated Domineralizer System l
The contaminated demineralizer nyctem has two 4" lines which connect to the fuel pool and transfer pool.
The valven isolating i
the 4" lines from the fuel pool and transfer pool are closed, and l'
only operated when high capacity make-up in needed.
There is no i
significant alphon potential on the line to the transfer pool 1
because it does not go to a-low enough elevation in the pool.
The contaminated domineralizer nystem line to the SFP passes through the transfer pool on a path which goen through a low l
elevv ion.
Thia line could siphon water only if the line were to break twice, once in the transfer pool, and once outside of it at i
a lower elevation.
When the SFP gates are installed, a
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hypothetical siphon would only lower the level of the transfer.
l pool.
Dresden Station will either modify the line by October 31, t
1994 no that it can not ciphon the SFP or transfer pool below the technical apecification limit, or demonstrate that the probability j
of a double break is so low that thia line is not a concern.
l-Requested Action 4.
I Enaure that operating procedures addrena conditiona and observationa that could indicate changen in SFP level and address appropriate maintenance, calibration and curveillance of available monitoring equipment.
This should include any leak detection system.
Responne to Requested Action 4.
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The Operating Department is recording both the fuel transfer pool and storage i
pool levels and any water additionn every shift in accordance with approved j
temporary changen to station proceduree Permanent operating procedures are currently being revised to collect thic data and describe actions to take if an abnormal losc in identified.
Theae procedure revisions will be in place by 4
j June 30, 1994.
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The water level and addition data in collected on a routine bacia and is being l
trended. A procedure for trending this data and describing actions to take j
after thene trends are reviewed will also be in place by June 30, 1994.
i The Unit 1 fuel poal low level alarm and fuel building Area Radiation Monitors 1
(ARMa)are calibrated on a annual bania, Both of these i
nurveillances/ calibrations are procedurally controlled by the Station i
Surveillance System.
1 The groundwater well program doncribed in the response to Requested Action.1.
j providen routine apent fuel transfer pool / transfer pool and spent fuel storage t
pool leak detection.
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