ML19262A883
| ML19262A883 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/06/1979 |
| From: | Finfrock I JERSEY CENTRAL POWER & LIGHT CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7912110260 | |
| Download: ML19262A883 (6) | |
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Jersey Central Power & Light Company
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Mornstown, New Jersey 07960 Madison Avenue at Punch Bowl Road
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A e-(201)455-8200 December 6, 1979 Mr. Dennis L. Ziemaan, Chief Operating Reactors Branch #2 Division of Operating Reactors U.S. Nuclear Regulatory Coninission Washington, D.C.
20555
Dear Mr. Ziemann:
Subject:
Oyster Creek Nuclear Generating Station Docket. No. 50-219 Additional Information Concerning Technical Specification Change Request No. 74 The enclosed information is in response to your questions concerning Oyster Creek Technical Specification Change Request No. 74.
Your prompt consideration of this change request would be appreciated since our outage planning and scheduling are based on approval of this change.
Very truly yours,
@l J)
Ivan R. Finfr ck, J.
Vice Preside.
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Jersey Central Power & Light Company is a Member of the General Public Utilities System
1.
Khy is the torus to be drained, for how long will it remain empty, and how often will such draining take place?
ANSWER:
The torus is being drained, so modifications can be made to the Park I containment.
These modifications are required to resolve Mark I containment concerns.
The torus is to be drained for the upcoming Cycle 9 ceload and the following Cycle 10 reload to accomplish the modifications. At present, no further drainings are planned but this is subject to change due to possible ruture modifications or maintenance.
It is planned to commence draining the torus approximately two (2) days into the Cycle 9 and Cycle 10 outages and maintain the torus drained throughout the outages until the schedule nodifications are completed.
It should be noted that the present Oyster Creek Technical Specification does allow the torus to be drained.
The Technical Specification Change Request now being subnitted, modifies the present i
intial criteria for draining to allow the torus to be drained earlier into the outage.
2.
h*nat safety limit on vessel water level do you propose during periods when
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the torus is drained?
j ANSWER:
The safety limit on vessel water level will remain as specified in the Oyster Creek 'Ibchnical Specifications, Section 2.1.D.
"During all modes of reactor operation with irradiated fuel in the reactor vessel, the water level shall not be less than 4 '-8" above the top of the normal active fuel zone."
3.
Describe the circumstances including operator errors, equipment failures, pipe breaks, seismic events, etc., which could result in a loss of vessel inventory during the period for which the torus will be empty.
ANSWER:
In this discussion, we need only evaluate those penetrations which would allow vessel water level tc fall below the 4 '--8" level above the active fuel.
This is the safety limit level as specified by Oyster Creek Technical Specifications.
The five major categories of penetrations are (1) the control rod drive (CRD) system, (2) the recirculation system, (3) the liquid poison systen, (4) instrument lines, and (5) the reactor vessel drain line.
Directly connected to the recirculation system are the emergency condenser system, reactor shutdown cooling system, cleanup demineralizer system, and instrument lines.
The majority e components of these systems are outside the drywell.
The liqui i
poison system penetration also supports two core Delta P instrument i
sensing lines which terminate outside the drywell.
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The probability of a pipe break or equipment failure which results in vessel draining is extremely remote.
The systems discussed above normally operate under a high temperature-high pressure environment.
During torus draining, the vessel is required to be below 212 F and vented.
The piping will therefore be seeing a f ar less severe environment than during normal power operation. Since the equipnent and piping are designated for normal operation, it is highly unlikely that this type of failure will occur.
The systems and components listed above are d signed to withstand a safe shutdown earthquake (SSE) and remain functional. 'Ihe exception to this is the cleanup domineralizer system which is seismic category II.
The isolation valves for this system are seismic category I and are capable of isolating the cleanup demineralizer system from the recirculation system in the event of systen or component failure.
Improper valve operation and maintenance activities are the most common operatot errors which could result in vessel draining. These errors are minimized through continuous maintenance training programs, plant procedure implementation, such as the requirement to prohibit work cn any systems which could have the potential of draining the vessel while the vessel water level is not above the 117 foot level, and operator training.
The response to gaestion 4 will discuss the break locations.
4.
For the most rcpij rate of inventory loss identified in the response to question 3, describe how it will be assured that the vessel water level will not fall below the safety limit. Your response should include consideration of:
(a) Systems to detect low water level and initiate automatic or manual response and set points for such initiations.
(b) specific systems and piping runs and valves to deliver makeup inventory, and a comparison of the makeup rate to the rate of inventory loss.
(c) time required for pumps to attain full capacity, for operators to perform manual functions etc.
(d) an evaluation of the minimum vessel level during the event.
ANSWER:
It was intended to show in question 3 that the probability of an event which results in vessel draining is extremely remote. Ilowever, there are actions which can be taken in the unlikely event of a loss of ves.sel inventory should occur.
With the approval of this technical specification change request, there will be two conditions that the plant can be in while the torus is drained. These two conditions both concern the water level in the reactor vessel.
First, as presently allowed by the Technical Specification, the reactor vessel head, fuel pool gate, and i
separator-dryer pool gate are removed and the water level is above elevation 117 feet, and secondly with the approval of the 'Ibchnical 1528 003
3 Specification Change, the vessel water level will be at normal shutdown level with the condensate storage tank level required to.be above the 30 foot mark.
After reactor shutdown to commence the outage, the reactor vessel will be cooled below 212 F and vented. We condensate storage tank will be filled to above the 30 foot mark and the core spray system will be lined up to take suction on the condensate storage tank.
The torus will then be drained.
Once draining has comenced, no work will be allowed to be performed which could have the potential of draining the vessel until plant conditions discussed below are met.
There are two general ?ocations, which we are concerned with, where a leak could occur.
The first would be draining of the vessel to outside the torus. In the event this should occur, when vessel water level reaches the low-low reactor water level trip ( 2 7'-2" above the active fuel) setpoint, an alarm is sounded in the control room alerting the operators, and a reactor isolation trip occurs shutting the isolation valves associated with the systems discussed in question 3.
The action is sufficient to isolate all breaks outside the torus without exceeding the safety limit for vessel level.
The core spray j
pump can be manually started to take suction on the Condensate Storage i
Tank if required to raise reactor vessel level.
i The other location where draining could occur would be inside the torus. There are two possible locations where this could occur.
The first would be from the control rod system. This is minimized by not allowing maintenance to be performed on the system.
The other location would be if a recirculation pump seal should fail. We pump seals are monitored in the control room and alarms will annunciate alerting the operator of excessive leakage.
The operator has sufficient time to isolate the affected pump before significant reactor vessel level is lost.
Prior to commencing the refueling operation, the reactor vessel level will be raised to the 117 foot level and the fuel pool gate and separator dryer gate will be removed. By completing this action, we now meet the present criteria for allowing the torus to be drained as is currently stated in the Technical Specification.
This condition was analyzed in our original subnittal for draining the torus dated January 11, 1977.
The limitation for performing maintenance on the vessel can now be lifted. This now allows work to be performed on the control rod drive blades.
This is significant because a path could be established to drain the core during control rod maintenance if a drive were removed while the associated blade was not back-seated, or worse, if the blade were completely removed following removal of the drive.
This could result in a 1300 gpm leak.
This is the largest leak that can be postulated during refueling.
It would take 5.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> for the water to drain down to the vessel flange, and an additional 0.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for the water level to reach the top of the active fuel.
(This ignores the fact that the leak rate 1528 004
decreases as the water level, and thus the driving head decrease).
During this time, various actions would be taken to stop the leak and to maintain water over the core. The immediate action to stop a leak through a control rod drive penetration would be to seat the blade and replace the drive.
In any draining situation, water could be supplied from a number of independent sources. Make up to the spent fuel pool surge tanks could be initiated manually using the condensate transfer system draining on the condensate storage tank. Water from the condenser hotwells can be added to the reactor vessel using the condensate system. The fire protection system can add water to the reactor vessel via the core spray headers or via hoses to the refueling cavity.
5.
hhat are the seismic and electrical qualifications of the systems you have specified to mitigate vessel inventory losses while the torus is drained?
ANSWER:
The condensate storage tank and associated piping are seismic category II qualified. Analysis performed on the condensate storage tank shows that it meets operating basis earthquake (OBE) criteria.
The core spray system is seismic category I qualified and its associated electrical systems meet IEEE 323 criteria.
6.
hhat does the phrase "and the torus is mechanically intact" in 3.4. A.10.d mean?
ANSWER:
The phrase "and the torus is mechanically intact" means that the torus is capable of holding water. Tnis is to ensure that water inventory is not lost in the unlikely event a drain path is established from the reactor vessel to the torus.
7.
How do you distinguish between work which could drain the vessel to below the level "4'-8" above the top of the active fuel" and other work which would not result in such a draining?
Why not prohibit all work which could have a potential for draining the vessel to any level?
ANSUER:
By reviewing the work package, the Group Shift Supervisor will be able to determine if it affects any of the systems discussed in question 3 which could provide a drain path to lower water level below the 4'-8" level.
i There is no reason to prevent all work from being performed. Tne i
reason we specified that no work would be performed which had the 1528 005
Potentie' -' draining the vessel to the 4 '-8" level was to minimize the po?..
- al for operator error while the vessel water 1cvel is at the nce
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shutdown level. Although the core spray pump when started can deliver makeup inventory (3400 GPM) faster than the postulated largest leak (1300 gpm) during refueling, there would only be approximately 15 minutes to take corrective action.
8.
Explain more fully the implication of the " note" on page 3.4-lb.
ANSWER:
The note was added to eliminate the 30 foot storage tank requirement while transferring water between the condensate storage tank and the vessel, provided that the total combined volume of water in the condensate storage tank and vessel exceeds 330,000 gallons.
This volume was determinei as explained ii the safety evaluation, to be the minimum required for core spray pu np operation and still maintain water inventory above the 4 '-8" levol in the core.
The reason we added the note was to prevent the processing of excessive amounts of water when draining the vessel to normal levels after refueling. Also, there is not sufficient volume in the condensate storage tank to drain the amount of water required to lower reactor vessel level af ter refueling operations if the condensate storage tank is filled above the 30 foot level.
9.
Has a special procedure been written to guide operators through the mitigation of a vessel draining event with the torus drained?
ANSWER:
Procedures are being developed to guide operators through the mitigation of a vessel draining event with the torus drained.
These procedures will be reviewed and approved by the PORC and in place prior to torus draining.
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