ML19344F223
| ML19344F223 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/02/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19344F222 | List: |
| References | |
| NUDOCS 8009120650 | |
| Download: ML19344F223 (3) | |
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NUCLEAR REGULATORY COMMISSION UNITED STATES 3
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,J SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 57 TO FACILITY OPERATING LICENSE NO. DPR-50 METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER AND LIGHT COMPANY PENNSYLVANIA ELECTRIC COMPANY THREE MILE ISLAND NUCLEAR STATION, UNIT NO. 1 DOCKET NO. 50-289 Introduction By letter dated September 7,1977, as revised by letteri dated October 21, 1977, March 31, 1980 and May 20, 1980, Metropolitan Edison Company (Met Ed) requested amendment of Appendix A to Facility Operating License No. DPR-50 for Three Mile Island Nuclear Station, Unit No. 1 (TMI-1). The change would ensure that proper flow resistances are maintained in High Pressure Safety Injection / Low Pressure Safety Injection (HPSI/LPSI) Systems throughout plant life. To ensure proper flow resistance, the proposed changes to the Technical Specifications modifies surveillance requirements on the throttle valves.
Discussion and Evaluation The HPSI and LPSI system designs of many Pressurized Water Reactors (PWR's) utilize a common low pressure and a comon high pressure header to feed the several cold (and in some cases hot) leg injection points. Maintenance of proper flow resistance and pressure drop in the piping system to each in-jection point is necessary to:
(1) prevent total pump flow from exceeding runout conditions when the system is in its minimum resistance configuration; (2) provide a proper flow split between injection points in accordance with the assumptions used in the Emergency Core Cooling System-Loss of Coolant Accident (ECCS-LOCA) analyses; and (3) provide an acceptable level of total ECCS flow to all injection points equal to or above that assumed in the ECCS-LOCA analyses.
Some plants, have motor operated valve (s) in the lines to each injection point that have stops which are set during pre-operational flow testing of the plant to insure that these flow requir'ements are satisfied.
On other plants, electrical or mechanical stops on the Safety Injection Systems's isolation valve (s) are used for this purpose.
By letter dated July 1,1977, we requested all nuclear stations which use HPSI and LPSI throttle valves or other means to control flow to propose changes to their Technical Specifications.
These changes are to include a surveillance program that assures an acceptable level of total ECCS flow to all injection points during ECCS operation.
Upon restart TMI-l will utilize cavitating venturies in each of the injecting lines in the HPSI system to satisfy EC'CS flow requiremte and to prevent pump runout condition during system operation.
- Dosisofo so
TMI-l By letters dated September 7,1977 and October 21, 1977 Met Ed responded to our request by proposing a surveillance program utilizing limit switches for valves in the HPSI system and mechanically locked valves in LPSI system to satisfy ECCS flow requirements. By letters dated !%rch 31, 1980 and May 20, 1980, Met Ed revised the proposed surveillance requirement to agree with the modifications to the ECCS. These modifications consist of installing cavitating venturies in each injecting line to thrott7e the HPSI by flow cavitating when reactor system pressure falls to approximately 600 psig, eliminating the need for motor operated valves to perform this same function. Furthermore, the cavitating venturies in each injection leg are sized to provide a proper flow split between injection points to meet the requirements established in the ECCS-LOCA analysis.
In the report titled " Recommended Requirements for Restart of TMI-1" Supplement 1, Part 3 response to Question 1, Met Ed has conmitted to hydraulically test the ECCS prior to restart to assure that the assumed flows in the LOCA analysis are met.
The NRC will witness the hydraulic field tests and review the test results to assure the measured flows meet the assumed flows in the ECCS-LOCA analysis. Het Ed will further confirm that the maximum stress level due to vibratory loads in the HPSI pipe runs during cavitating modes will be below the fatigue limit of the pipe materials.
Because the motor operated valves are not needed to throttle flow to prevent pump runout conditions, we conclude that the valve stops are not required, thus elimi-nating the need for a surveillance requirement regarding this matter. These valves, however, are used to isolate HPSI from the reactor coolant system and are actuated (open) when the high pressure injection is required for emergency core cooling. Met Ed is required by the Technical Specifications to test this function and a change to the Technical Specifications has been proposed to specifically identify the valves to be tested. We conclude that this change would provide addi-tional assurance that the proper valves will be tested and thus the proposed change is acceptable.
Met Ed has also proposed to increase the scope of the surveillance requirements for HPSI systems to include testing following maintenance or modifications that a f fect system flow characteristics. This proposed requirement will provide addi-tional assurance that this system will function as assumed in the ECCS analysis l
and therefore these additional requirements are acceptable.
In order to assure that an adequate flow will be available to all injection points, Met Ed proposed a minimum flow requirement per high pressure injection pump
(>500 gpm at discharge pressure of >600 psig) as part of the surveillance program.
t tee flow and pressure parameters are Eased on the assumed flow of the small break i
ECCS analysis. We requested additional information in order to further evaluate these surveillance parameters. An evaluation by B&W was submitted by Met Ed which contains the requested information (letter to D. G. Slear, GPU, from G. T. Fairburn, B&W, "HPSI Flows During Small Break Transients", April 16, 1980). The design HPSI flow rates for TMI-l were comared to those used in the B&W analysis cf small breaks, and the TMI-l HPSI flow rates were found to be greater than those used by B&W above 600 psig, and slightly lower below 600 psig. The effect of the TMI-l flow rates was found to have an insignificant effect on the consequences of a small break, however For the small size producing the highest peak cladding I
temperature (0.07 f t ) use of the TMI-l flow rates increased the peak cladding temperature by only 5"F, from 1095" to ll00*F,so that compliance with the 10 CFR 50.46 criteria is maintained. We conclude that the surveillance parameters and the HPS! flow rates for TMI-l are acceptable.
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. TMI-1 Met Ed has taken an exception to our suggested surveillance of the throttle The basis for this position is that valve position stops for the LPSI system.
the throttle valve position stops are not needed for protection against pump runout conditions, since if the throttle valves and all other system valves are This is placed in a full open position pump runout conditions will not occur.
the case because of the system's high resistance (high pressure drop) at high flow rates (m3000 gpm) coupled with the pumps low head characteristic (+100 psig).
f urthermore, the controlability of the throttle valve would be reduced if the (controlability) that is position valve stops would be used, a valve feature needed by the reactor operator to control flow during long term accident conditions.
During power operation the LPSI throttling valves are throttled to a position enabling the system to provide adequate flow to meet ECCS-LOCA (large break) require-The basis ments as well as decay heat removal during plant shutdown conditions.
for the throttled position of the valves is not to protect against pump runout conditions but to prevent excess wear on the pumps and to eliminate valve position changes when the operating mode of the plant is changed from power operation to shutdown cor.ditions.
By procedures the reactor operator is required to verify the LPSI flow when operation of the system is initiated and the flow would be manually adjusted if During prolonged operation of the LPSI system, the throttle valve necessary.
The positions are assured by maintaining the handwheels in a locked position.
proposed Technical Specifications require Met Ed to verify the correct valve position by rbservation within four hours of each valve stroking or valve maintenance.
Based on the ebove, we agree with the licensee that the valve stops are not needed and the intent of the surveillance is being met. We conclude that the position taken by Met Ed is acceptable.
Environmental Consideration We have determin.ed that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and Having made will not result in any significant environmental impact.
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 651.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
rrnelusion We have concludml, based on the tunsiderations distu u ed above, that:
(1) because the amenilment 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 br;ission's regulations and the issuance of the anendment will not be inimical to the comon defense arid security or tc the health and safety of the public.
Date:
September 2,1980
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