ML19273B016
| ML19273B016 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 01/16/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19273B012 | List: |
| References | |
| NUDOCS 7902010276 | |
| Download: ML19273B016 (3) | |
Text
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p SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 41 TO FACILITY OPERATIfiG LICENSE NO. DPR-39 AND AMENDMENT NO. 38 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDISON COMPANY ZION STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 Introduction By letters dated October 26, 1977 and October 5, 1978, Commonwealth Edison Company (the licensee) requested changes to the Technical Specifications appended to Facility Operating Licenses DPR-39 and DPR-48 for Zion Station, Units 1 and 2, respectively.
These changes would reduce the maximum pressurizer heatup rate from 200 F per hour to 100 F per hour and incorporate ECCS flow rate surveillance require-ments.
Background
Pressurizer Heatup Rate In August 1977, Mitsubishi Heavy Industries, Ltd., of Japan, noted an inconsistency in the pressurizer heatup rate stated in their Technical Specifications.
Specification 3.4.9 required a heatup rate of 200 F/hr; Specification 5.7.1, however, required a heatup rate of 100 F/hr.
This discrepancy was reported to the Westinghouse Electric Corporation (Westinghouse), who then reviewed their analysis of the pressurizer heatup rate and determined that the correct heatup rate is 100 F/hr, and that the correct cooldown rate is 200 F/hr; the Technical Specifications for Zion Station stated that pressurizer heatup and cooldown rates were 200 F/hr. Westinghouse then notified the Nuclear Regulatory Commission (the Commission) and the licensee of this problen, The requested amendment would correct the error in the pressurizer heatup rate limit.
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. ECCS Flow Rate The High and Low Pressure Safety Injection system (HPSI and LPSI) designs of many Pressurized Water Reactors (PWR) use a common low pressure and a common high pressure header to feed the several cold Maintenance of proper (and in some cases hot) leg injection points.
flow resistance and pressure drop in the piping system to each (1) prevent total pump flow from injection point is necessary to:
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 ass umptions used in the ECCS-LOCA analyses, and (3) provide an acceptable level of total ECCS flow to all injectionOn points equal to or above that assumed in the ECCS-LOCA analyses.
many plants, there are motor operated valve (s) in the l flow testing of the plant to insure that these flow requirements are On other plants, electrical or mechanical stops on the sa ti s fied.
Safety Injection System's isolation valve (s) are used for thisT purpose.
requirements.
While pre-operational HPSI/LPSI flow testing assured that the valves used to throttle flow have been properly set initially, we have con-cluded that periodic surveillance requirements are needed to assure that Conscquently, we requested all PWR these settings are maintained.
licensees to propose appropriate Technical Specification changes toWe incorporate periodic surveillance requirements for these values.
provided sample surveillance requirements to licensees for guidanceOu in developing proposed changes.
of throttle valve position stop settings, and verification of proper ECCS flow rate whenever system modifications are made that could alter flow characteristics.
Evaluation Pressurizer Heatup Rate In designing the pressurizer, Westinghouse performed a thermal stress analysis which analyzed the fatigue resulting from a heatup rate of This analysis meets the 100 F/hr and a cooldown rate of 200 F/hr.
standards of the ASME Code,Section III, which requires that the The usage factor represent the analysis be based on a usage factor.
i
, fraction of the fatigue life (the total amount of stress that a particular component is designed to handle), with a usage factor of zero implying that no stress has been exerted on the component, and a usage factor of one implying that the stress exerted on the component is equal to the amount of stress that the component is designed to handle.
For any piece of equipment, certain components For the pressurizer, this component receive nore stress than others.
is the surge r.ozzle, which has a usage factor of 0.9 for the design This usage factor is such that if the heatup numbers listed above.
and cooldown rates used in the analysis were exceeded more than a few times, the actual usage factor for the surge nozzle would exceed 1.0, Thus, we conclude that which is not allowable under the ASME Code.
reducing the heatup rate limit from 200 F/hr to 100 F/hr is necessary to maintain thermal stresses in the pressurizer to allowable levels.
For the same reasons, we further conclude that the cooldown rate limit presently listed in the Technical Specifications is adequate.
Because the current Technical Specification provision authorized higher rates of pressurizer heatup than the correct limit, the question arose as to whether the correct linit of 100 F per hour has been Discussions with Westinghouse indicate that this exceeded in the past.
This is because the systen capabilities and Technical is unlikely.
Specification limits on the rate of reactor coolant systen heatup and pressurization effectively preclude pressurizer heatup rates in Furthermore, in its letter of excess of 50 F to 75 F per hour.
26, 1977, the licensee indicates that the Zion Station operating October procedures have always used 100 F per hour as the maximum heatup rate.
Accordingly, we conclude that the only action required by Zion Station is modification of the Technical Specifications to reduce the limiting pressurizer heatup rate of 200 F per hour to 100 F per hour.
25, 1978 Westinghouse was requested to perform an audit On September review of the stress analyses for components of the reactor coolant pressure boundarv to assure that no similar inadvertent error appears in any other portion of the applicable Technical Specifications.
By 27, 1978 Westinghouse responded by stating that letter dated October l
in the past year it had carefully reviewed the stress analysis inputs i
I
. to the Technical Specifications for five separate plants and, in addition, is completing a very caref ul, rystenatic review on the generic June 15, 1978 version of the Westinghouse Standard Technical Specifications and if any further inconsistencies surface during this review process, suitable action would be taken (in the forun of the Westinghouse STS). We find this response acceptable.
ECCS Flow Rate The licensee responded to our request with respect to Zion Station by letters dated Septenber 19, 1977, September 3 and October 15,19/3.
Based on our review of these licensee subnittals, and discussions with the licensee, we have concluded that Zion Station's proposed increased surveillance requirenents will provide sufficient additional assurance that proper valve settings for ECCS flows and flow distribution will be naintained throughout plant life; and thus, the proposed changes are acceptable.
Environnental Consideration We have deterroned that the anendments will not authorize change in ef fluent types or total anounts nor an increase in power levels and will not result in any significant environnental inpact.
Having nade this deternination, we have further concluded that the amendnents involve an action which is insignificant fron the standpoint of environ-mental inpact, and pursuant to 10 CFR 551.5(d)(4), that an environnental inpact statenent or negative declaration and environmental inpact appraisal need not be prepared in c' :nection with the issuance of these anendments.
C o n c_l u s i o_n Ue have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered and do not involve a significant decrease in a safety nargin, the amendnents do 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 nanner, and (3) such activities will be conducted in compliance with the Connission's regulations and the issuance of these anendments will not be ininical to the connon defense and security or to the health and safety of the public.
Date: January 16, 1979