ML19262C618
| ML19262C618 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 01/25/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19262C617 | List: |
| References | |
| NUDOCS 8002140723 | |
| Download: ML19262C618 (5) | |
Text
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION 5
j WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0. 45 TO PROVISIONAL OPERATING LICENSE NO. DPR-16 JERSEY CENTRAL POWER & LIGHT COMPANY
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l 0YSTER CREEK NUCLEAR GENERATING STATION DOCKET N0. 50-219
1.0 INTRODUCTION
By letter dated September 24,1979 (Reference 1), Jersey Central Power
& Light Company (the licensee) has requested a Technical Specification change to allow draining the Oyster Creek torus under less restrictive conditions than currently required.
The torus is being drained so that modifications to the Mark I containme it can be made during the upcoming cycle 9 refueling outage and the followi ig cycle 10 refueling outage.
The planned modifications will improve the capability of the torus to withstand the stresses anticipated during blowdown of steam into the torus.
2.0 DISCUSSION The Oyster Creek suppression pool (torus) water serves two functions.
During power operation the torus water acts as the emergency heat sink for postulated accident or transient conditions involving a release of primary system energy through relief valves, safety valves, or coolant systen breaks. Under these conditions steam discharges into the suppression pool several feet below the surface of the water and is condensed.
The torus water is also the nonnal source of water for the emergency core spray system.
During events involving loss of reactor coolant inventory, a low water level signal initiates transfer of torus water though the core spray pumps into the reactor vessel.
Because loss of coolant inventory from the reactor vessel could occur during refueling from an event such as failure of a control rod blade seal and because a low level of decay heat is generated in the exposed fuel even after shutdown, the core spray systen is nonnally maintained fully operable which requires available torus water.
However, the current Technical Specifications allow the torus to be drained provided the vessel inventory is increased to the 117 ft. level with the vessel head, the fuel pool gate and the separator-dryer gate removed.
This 800214072.3
. assures that the worst credible leakage rate (1300 gallons per minute due to removal of a control rod blade and drive) from the vessel can be controlled to maintain an adequate level of water (4'8") above the top of the active fuel.
With the proposed change these measures would not be required, provided an adequate water supply resides in the condensate storage tank, and work which could result in lowering the reactor water level to 4'8" above the top of the active fuel is prohibited.
The proposed Technical Specification change would allow the torus to be drained earlier in the refueling outages, and would pemit an accelerated schedule for the Mark I modifications.
In support of the request for a change in Technical Specifications the licensee has sutmitted an initial analysis (Reference 1) and answers (Reference 2) to our request for additional information (Reference 3).
3.0 EVALUATION The current Technical Specifications permit the core spray system to be inoperable, including the torus being-drained, provided certain conditions are met. Approval for this was given in a previous license amendment (Reference 4).
Reference 1 contains the proposed changes to the Oyster Creek Technical Specifications.
The licensee requested that Specification 3.4.A.10 and 3.5-la be changed to pemit the core spray systs to be inoperable, i.e., the torus to be drained, when alternate conditions are met.
The alternate conditions are that (1) no work shall be performed which could result in lowering the reactor water level less than 4'8" above the top of the fuel and (2) the condensate storage tank (the makeup source of any lost reactor water) must contain a minimum of 360,000 gallons of water.
In Reference 3 we requested the licensee to identify the ways that loss of reactor vessel water could occur during refueling.
Their reply, Reference 2, indicated that the vessel penetrations which include the control rod drive system, the recirculation system, the liquid poison system and the instrument lines are all designed to remain functional and withstand a Safe Shutdown Earthquake (SSE).
Furthemore, with the reactor vented and the coolant system at less than 212"F, pipe breaks or system failure due to high pressure and taperature will not occur.
Only leaks inside the drywell need be considered.
All leaks outside the drywell will be teminated by automatic reactor isolation initiated when the water level reaches 7'2" above the top of the active fuel.
. Leaks from the recirculation system could occur through failed seals on the recirculation pumps.
However, even in the unlikely situation that the double seals on a given pump should fail simultaneously the leakage would be limited to a few gallons per minute by the metal thrust seal.
Systems connected to the recirculation system (including the emergency condenser system, the reactor shutdown cooling system, cleanup deminer-alizer system), can be isolated from the recirculation system with SSE qualified components.
Large leaks from the reactor vessel could occur during maintenance to the control rod drive system or by improper valve operation. The current Technical Specifications (Specification 3.4.7) prohibit such work during periods of reduced core spray system availability and the proposed change maintains this restriction.
The most severe postulated leak would result from complete removal of a control blade following removal of its drive (Refarence 2). This is precluded by administrative control of maintenance activities.
The resulting leakage rate of this very unlikely event,1300 gallons per minute, has been used as a basis for judging the capability of the system and the operators to mitigate losses of inventory.
Assuming a loss of primary system coolant inventory, the first indication from the reactor protection system would occur when the water level reaches 7'2" above the top of the active fuel. At a postulated net loss rate of 1300 gpn it would take 15 minutes for the water level to reach the safety limit (4'8" above the top of the active fuel).
Actuation of a single core spray pump (3400 gpm) during this time would be sufficient to prevent the safety limit from being exceeded.
The only operator action required during the 15 minute interval is to realign the core spray system to use water from the condensate storage tank.
This realignment only requires manual operation of one valve and 15 minutes is considered adequate time for this operator action.
However, we requested that there be at least two operable core spray pumps and system components to deliver rated core spray from the condensate storage tank to the reactor vessel when the vessel head is on the reactor and the reactor cavity is not flooded with water to the 117 foot elevation. The licensee has agreed and the proposed technical specification will be modified to include this requirement.
The licensee has also considered the adequacy of the combined water volume in the condensate storage tank and the reactor vessel.
There must be sufficient water to keep the core covered to the 4'8" level and assurance that the core spray system will function to replace iny water lost through a postulated leak.
The core spray can operate if there is water in the condensate storage tank or enough leakage water in the drywell to drain into the torus and fill the suction header of the core spray system.
The licensee detennined that 360,000 gallons of water in the condensate storage tank will be adequate.
This limit will be incorporated in the Technical Specifications and on this basis the proposed change is acceptable.
. 4.0
SUMMARY
Major leaks from the Oyster Creek reactor vessel while the torus is drained are very unlikely because: (1) the temperature and pressure of the primary system is low since the reactor is in cold shutdown and vented to atmospheric pressure, (2) the system penetrations are seismically qualified, and (3) special administrative controls are in effect when the torus is drained to prohibit maintenance which could cause major leaks.
Leaks outside the drywell could be terminated by automatic reactor isolation and therefore would not uncover the top of the active fuel. The most severe leak inside the drywell would not uncover the top of the active fuel or exceed the safety limit since adequate water inventory is provided to fill the bottom of the drywell, spill into the torus, and recirculate back to the reactor through the core spray system.
The proposed change in the Oyster Creek Technical Specifications will not result in an increase in the probability or consequences of an accident or transient previously considered and does not involve a decrease in safety margin. We therefore conclude that the change is acceptable.
5.0 ENVIRONMENTAL CONSIDERATION
We have detemined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and enviromental impact appraisal need not be prepared in connection with the issuance of this amendment.
6.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Date: January 25, 1980
-S-References 1.
Letter from Ivan R. Finfrock, Jr. of Jersey Central Power & Light Company (JCPL) to Director of NRR, Septaber 24, 1979.
2.
Letter from Ivan R. Finfrock, Jr. of JCP._ to Dennis L. Ziemann of NRC, Decsber 6,1979.
I 3.
Letter from Dennis L. Zimann of NRC to I. R. Finfrock, Jr. of JCPL, Novmber 15, 1979.
4.
License Amendment No. 21 to License No. DPR-16, February 4,1977.
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