ML20214F395
| ML20214F395 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 05/13/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214F393 | List: |
| References | |
| TAC-53327, TAC-53328, NUDOCS 8705260061 | |
| Download: ML20214F395 (5) | |
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'.g UNITED STATES g
NUCLEAR REGULATORY COMMISSION a
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WASHINGTON D. C. 20655
%**..j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENTS NOS.136AND 75 TO
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FACILITY OPERATING LICENSES DPR-57 AND NPF-5 GEORGIA POWER COMPANY OGLETHORPE POWER CORPORATION MUNICIPAL ELtGIRIG AUTHORITY OF GEORGIA CIIT OF DALTON, GtVKGIA EDWIN I.. HATCH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-321 AND 50-366 INTRODUCTION The Technical Specifications (TS) for Hatch Units 1 and 2 do not have a closure time requirement for the Scram Discharge Volume (SDV) vent and drain valves. By letters dated September 19, 1983 (Ref. 1) as supplemented by letters dated December 14,1983 (Ref. 2), December 20, 1983 (Ref. 3) and September 13, 1985 (Ref. 4), the licensee proposed to include maximum closure times for the subject valves in the surveillance TS.
The closure times would be 60 seconds.
By letter dated January 6,1986 (Ref. 5) the licensee further proposed to change the closure time for Hatch Unit 1 to 45 seconds. The changes would affect TS 4.3.I.2.b.1 for Unit 1 and TS 4.1.6.1.c.1 for Unit 2.
The proposed change would add the specified closure times as Technical Specification requirements for the Hatch Units.
Surveillance criterion 1 of the generic Safety Evaluation Report for BWR Scram Discharge System (Ref. 6) states that closure in less than 30 seconds (a GE specification)isacceptable. However, closure tests at Hatch Units 1 and 2 indicate that closure times for the. Hatch valves are very near 30 seconds and that a 30 second Technical Specification limit would leave little margin.
Accordingly, the licensee has proposed longer closure times. The NRC Staff's evaluation of the licensee's justification of the proposed closure times is set forth below.
EVALUATION During a scram, water from the control rod drive (CRD) system is released into a scram dischar normally open, ge volume (SDV). The SDV vent and drain valves, which are close automatically on receipt of a scram signal. Upon com-pletion of a reactor scram, with all control rods fully inserted, water leaks past the CRD seals from the reactor and continues to flow into the SDV. This flow continues until the pressure in _the SDV equals the reactor pressure, g52%gIk N P
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_ R General Metbcdology GE provided an analysis for the licensee entitled " Relaxation of Scram Discharge Volume Vent and Drain Closure Times" (Ref. 7). Major assumptions included:
a Scram time equals 5 seconds.
b A displacement volume of 0.765 gallons per individual CRD.
c An average expected post-scram leakage flow of 3 gpm per individual CRD.
d) An SDV drain flow prior to isolation of 50 gpm.
e) A minimum SDV volume of 482 gallons.
j With a norwel scram and closure time of 60 seconds the following major cancerns
'were considered.
Overfilling During closure, overfilling is prevented if SDV inflow minus outflow is less than the SDV volume.
The capacity of the SDV, bounded by Hatch 1, was shown to be adequate to prevent overflow.
Temperature Increase Based on GE test data, the maximum temperature prior to closure would be 212F. With the further assumption of atmospheric pressure in the SDV at valve closure, there would be no flashing. Hence there would be no steam discharge through the vent and drain valves. See Hydrodynamic Loads below for a further discussion.
Radiation GE stated that since the SDV will not overflow, no additional radiological concern is generated due to the longer closing time.
Hydrodynamic Loads GE referred to a prior qualitative analysis (Ref. 8) which concluded that the longer valve closure time would not introduce any additional hydrodynamic forces. Steam / water hammer following valve closure would be minimal since the temperature in the SDV is below flashing.
The staff accepted the GE methodology; however, additional justification was requested of the licensee to substantiate the prevention of overfilling the SDV during normal scram.
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Sixty Second Closure Time i
By letter dated November 18, 1985 (Ref. 9), the licensee established the
- i following:
The post-scram leakage into the SDV was detemined based upon measured data from two cycles of' Hatch Units 1 and 2 CRD stall flow, and GE correlations of post-scram leakage versus CRD stall flow (Ref.10). The inflow leakage exceeded the GE assumption -(Ref. 7) by 0.4 gpm.
4 The drain flows of previous analyses (Ref. 7 and 8) were corrected, j
An "as built" volume of the SDV for Unit 1 of 549 gallons was provided.
j This value exceeds that used in previous analyses (Ref. 7 and 8).
Using the Ref. 9 post-scram leakage and "as built" volume, the SDV was reanalyzed. For conservatism, it was further assumed that the SDV drainage 3
flow was zero. The results showed that the-SDVs for Hatch Units 1 and 2 would not overfill on the basis of a 60 second closure time.
Forty-Five Second Closure Time After further discussion with the staff and by letter dated January 6,1986 (Ref. 5), the licensee requested that the TS for the SDV closure time of Hatch Unit I be 45 seconds. The Unit 2 proposal for 60 seconds remained unchanged. Calculations were provided which add'ressed the staff concern of l
overfilling the SDVs during scram.
Major assumptions in this analysis were:
Use of the oost-scram SDV inflow as already described above from Ref. 9.
I The value, extrapolated from measured data, was higher and thus more
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appropriate than the analyses of References 7 and 8.
i Use of individual "as built" SDV volumes for both Hatch Units 1 and 2, rather than the bounding value of Hatch Unit 1.
Prior analyses of i
References 7 and 8 used a smaller volume. While not as conservative, j
the "as built" volume is acceptable to the staff.
By these analyses, the licensee demonstrated that the SDVs for Hatch Units 1 gv[9 and 2 would not overfill during a nomal scram.
By letter dated December 14, 1983 (Ref. 2), the licensee stated that Hatch Unit I had operated with a closure time of approximately 49 seconds for several years without apparent problems. This provides further evidence to support the analysis demonstrating that the SDV will not overfill.
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With regard to the staff's concern for 50V inflow, the licensee further stated i
that post-scram CRD leakage was limited by the licensee's program of CRD stall flow testing and drive rebuilding. The stall flow testing is performed at Dower on all drives during a particular Cycle.
Based on the results of this testing, certain drives are rebuilt during the following outage. The drives selected for rebuilding are those 10% with the highest leakage figures, as well as any other drives whose leakage exceeds 4 gom.
l We find the licensee's analyses and the CRD stall flow testing and drive rebuilding program acceptable in demonstrating that the SDV will not overfill i
during a normal scram for Units 1 and 2.
We have reviewed the infonnation provided by the Georgia Power Company relative to the proposed TS modifications for Hatch Units 1 and 2 for SDV vent and drain
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valve closure time.
Based on the considerations as discussed above, we have concluded that the proposed technical specification changes are acceptable' with SDV vent and drain closure times of 45 and 60 seconds for Hatch Units 1 and
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2, respectively.
j ENVIRONMENTAL CONSIDERATIONS i"
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined'in 10 CFR Part 20.
The staff has detennined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any er-fluents that may be released offsite, and that there should be no significant increase in individual or cumulative occupational radiation exposure. The Connission has previously issued a proposed finding that the amendments in-volve no significant hazards consideration and there has been no public connent on such finding. Accordingly, the amendments meet the eligibility 4
criteria for categorical exclusion set forth in 10 CFR 951.22(c)(9).
Pursuant to 10 CFR 551.22(b), no environmental impact statement or environmental assess-ment need be prepared in connection with the issuance of the amendments.
CONCLUSION 1
The Connission made proposed detenninations that the amendments involve no significant hazards consideration which were published in the Federal Resister i
(49 FR 7161) on February 27, 1984, (50 FR 46213) on November 5, 1985, anc i
(51 FR 18683) on May 21, 1986, and consulted with the state of Georgia. No public connents were received, and the state of Georgia did not'have any comments.
We have concluded, based on the considerations discussed above, that:
(1)there 1s reasonable assurance that the health and safety of.the public will not be en-j dangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Connission's regulations, and the issuance of the amendments will not be inimical to the connon defense and security or to the health and safety of the public.
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REFERENCES 1.
Letter from G. F. Head, Georgia Power Company, to John F. Stolz, NRC,
" Scram Discharge System Technical Specifications," September 19, 1983.
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2.
Letter from G. F. Head, Georgia Power Company, to John F. Stolz, NRC,
" Change to SDV Technical Specification Submittal," dated December 14, j
1983.
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-3.
Letter from L. T. Gucwa, Georgia Power Company, to John F. Stolz, NRC, i
" Errata to Letter of December 14, 1983." December 20, 1983.
i 4.
Letter from J. T. Beckham, Jr... Georgia Power Company, to John F. Stolz, NRC, " Request to Revise Technical Specifications: Add Scram Discharge l
Volume Vent and Drain Valve Closure Time Requirement " September 13, 1985.
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Letter from J. T. Beckham, Jr., Georgia Power Company, to D. Muller, NRC, q
" Revision to Previous Submittal: SDV Vent and Drain Valve Technical j
Specifications," January 6, 1986.
'l 6.
Generic Safety Evaluation Report, BWR Scram Discharge System, December 1, 1986.
7.
General Electric Report MDE 103 1184, Rev 1 "Edwin I. Hatch Units 1 and 2 Relaxation of Scram Discharge Volume Vent and Drain Valve Closure Times,"
December 1984.
4 8.
Letter f.om J. T. Beckham, Jr., Georgia Power Company, to John F. Stolz, NRC, " Scram Discharge Volume Vent and Drain Closure Times," December 22, 1-1983.
9.
Letter from J. T. Beckham, Jr., Georgia Power Company, to John F. Stolz, NRC, " Scram Discharge Volume Vent and Drain Valve Closure Time Technical Specifications," November 18, 1985.
10 General Electric Topical Report NEDO-24342, "GE Evaluation in Response to i
NRC Request Regarding BWR Scram System Pipe Breaks," April 1981.
Principal Contributors:
D. Katze L. Crocker i
Dated: May 13, 1987 I
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