ML20236T610
| ML20236T610 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/17/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20236T606 | List: |
| References | |
| NUDOCS 8712010396 | |
| Download: ML20236T610 (3) | |
Text
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UNITED STATES E'
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,{ j; NUCLEAR REGULATORY COMMISSION j
WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 124 TO FACILITY OPERATING LICENSE NO. DPR-32
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AND AMENDMENT NO.114 TO FACILITY OPERATING LICENSE NO. DPR-37 VIRGINIA ELECTRIC AND P0 LIER COMPANY SURRY POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-280 AND 50-281 I.
INTRODUCTION B}'letterdatedSeptember 25,'1987, as superseded October 7. 1987, Virginia Electric and Power Company (the licensee) requested amendments
'to Facility Operating License Nos. DPR-32 and DPR-37, issued to the licensee for operation of the Surry Nuclear Power Station, Units 1 and 2, located in Surry County, Virginia.
The proposed amendments would revise Section 4.7, " Main Steam Line Trip Valves" of the Surry Units 1 and 2 Technical Specifications by removing the partial-closure test specified in Sections 4.7A and 4.7B and replacing it with a more rigorous full-closure test to be performed at each start-up.
Also, the proposed amendments would remove the discussion of the partial-closure test from the Bases section of the Technical Specifications (TS).
The proposed amendments would also revise the full-closure test frequency and test conditions, as well as the full-closure test acceptance criteria for the main steam trip valves. A parallel specification in Table 4.1-2A would also be revised to be consistent with the proposed revision to TS 4.7.
Finally, the Bases section would be expanded to include a discussion of the accident analysis assumptions and derivation of the acceptance criteria for the valve closure time.
II. EVALUATION The current TS for Surry Units 1 and 2 require the licensee to perform a partial-closure test of Main Steam Trip Valves (MSTV's) before each startup.
The partial-closure test rotates the valve disk three degrees to verify the freedom of the valve disk to function as required. The current TS also require a full-closure test for MSTV's before startup from every cold shutdown. The licensee has indicated that, in practice, a full-closure test is performed before each startu) regardless of whether the unit is starting from cold shutdown or hot slutdown. Thus, the full-closure test satisfies the intent and frequency requirements for both tests. The licensee has proposed to perform a full-closure test before each startup instead of at each cold shutdown as required by the current TS. The kR 0
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,, full-closure test will cover the intent and frequency requirements for the partial-test delineated in current TS. Thus, the partial-closure test is not necessary and therefore, the removal of partial-closure test require-ment is acceptable. Also, as noted above, the licensee has perform a full-closure test for the MSTV's at each startup (proposed to regardless of whether the unit is starting up from cold or hot shutdewn) instead of at each startup fron a cold shutdown condition. This will increase the frequency of full-closure tests from the current TS. Also, the licensee may perform the test during hot shutdown, which is more representative of plant conditions the valves would experience if called upon to perform their safety function. The staff considers both of these changes to be appropriate and therefore acceptable.
Also, in order to make the test procedures consistent with the interpre-tation of ASME Section XI requirements, the licensee has proposed to change the acceptance criter. ion for MSTV closure time from the present 5 seconds to a total of 9 seconds, consisting of a 4 second period from a manual initiation of the stean line isolation to initiation of MSTV motion, and a 5 second period for MSTV closure time from the full-open to the full-closed position. The licensee stated that the proposed closure times closely reflect the current bounding main steam line break aralysis discussed in Section 14.3.2 of the Surry Updated Final Safety Analysis Report. The licensee originally submitted the above analysis by a letter dated September 13, 1953, to support the removal of the TS for the boron injection tank. The above analysis assumes a 5 second delay from the time the measured process variables (e.g., steam line flow, steam line pressure) reach the main steam line isolation setpoints to the initiation of MSTV motion, followed by an additional 5 second ramp closure of the valves.
In proposing the above time periods, the licensee has conservatively allowed 1 second for instrument response time delay from the time the process variable reaches the setpoint to initiation of bleed-off of instrument air from the main steam trip valve air cylinders. The bleed-off time is estimated to be 4 seconds. The MSTV closure time is also estimated to be 5 seconds. Under actual steam line break conditions, it is expected that the HSTV closure time (stroke time) will be much less than 5 seconds. Also, closure of the MSTV's under test conditions requires venting of the control solenoid operated valves (SOV's) located in the auxiliary building. The long run of air piping between the 50V's and the MSTV air cylinders results in a relatively large volume of air, which must bleed-off before the valves will close.
Under test conditions, air pressure must decrease from a nominal 90 psig to approximately 32 psig before the valve will start to close. Under full-steam flow conditions, not only will the steam flow assist in rapidly closing the valves, but rupture disks in the air cylinders will assist faster closure of MSTV's.
The staff has reviewed the licensee's assumptions used in the main steam line break analysis, and determined that the proposed test acceptance criteria for MSTV closure times are consistent with the analysis. Also, the staff recognizes that under high steam flow during main stean line break conditions, the MSTV will close in much less time than the test condition because steam flow will assist the valve closure and the rupture
.. 1 disks in the air cylinders will depressurize the air cylinders faster, which will assist valve closure. Also, using the above conservative assumptions, the licensee has demonstrated that the offsite dose conse-quences from a main stean line break will be a small fraction of the 10 CFR Part 100 guidelines. Therefore, the proposed test acceptance criteria for MSTV closure time are acceptable.
In addition, the licensee has proposed to change the Bases for TS 4.7 and Table 4.1-2A of the Surry TS to reflect the proposed changes in TS 4.7.
Both of these changes are acceptable as they provide consistency in the TS.
III. ENVIRONMENTAL CONSIDERATION These amendments involve a change in the installation or use of facilities components located within the restricted areas as defined in 10 CFR 20 and changes surveillance requirements. The staff has determined that these amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite and that there is no significant increase in individual or cumula-tive occupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding.
Accordingly, these amendments meet the eligibility criteria for categor-ical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
IV. CONCLUSTON We have concluded, based on the considerations discussed above, that (1)thereisreasonableassurancethatthehealthandsafetyofthehublic will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
j Dated: November 17, 1987 i
Principal Contributor:
C. P. Patel i
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