ML20246L671
| ML20246L671 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/11/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246L669 | List: |
| References | |
| NUDOCS 8905180374 | |
| Download: ML20246L671 (4) | |
Text
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l UNITED STATES Y
4 NUCLEAR REGULATORY COMMISSION y
E WASHINGTON, D. C. 20656
\\...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 115 TO FACILITY OPERATING LICENSE N0. DPR-77 AND AMENDMENT NO. 105 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
In letters dated May 26, 1988 and February 23, 1989, the Tennessee Valley Authority (TVA) requested changes in the Technical Specifications (TS) forSequoyahNuclearPlant(SQN), Units 1and2,regardingtheacceptance criteria for auxiliary feedwater pump (AFWP) differential pressure surveillance testing.
Specifically, the proposed changes revised Surveillance Requirement (SR) 4.7.1.2.a for each unit's TS to add pump-specific differential pressure test values for each AFWP. These changes were necessitated by modifications to the AFWPs and/or their associated piping flowpaths.
In addition, the bases sections associated with these SRs were revised by the proposed TS changes. The proposed TS change is number 88-02 for Unit 2 and 88-24 for Unit 1.
The staff developed concerns, with the May 26, 1988 submission of TS change number 88-02 for Unit 2, relating to the method used to incorporate test instrument error in the generation of the AFW pump curves, system resistance curves, and SR 4.7.1.2.a acceptance criteria.
In response to the staff concerns, TVA reevaluated their calculations and provided revised proposed TS change pages for SR 4.7.1.2.a and its associated bases. These revised pages, along with the corresponding calculation revision, were forwarded as additional information as l
part of the February 23, 1989 request for TS change number 88-24 for SQN Unit 1.
The TVA letter dated February 23, 1989 applied for changes on the AFWP for the Unit 1 TS.
It also applied for changes on the AFWP for the Unit 2 TS. The latter changes superseded the proposed changes in the TVA letter dated May 26, 1988.
In the Federal Register Notice of consideration of issuance of an amendment (54 FR 11844) published on March 22, 1989 for TVA application dated February 23, 1989, it was acknowledged that the May 26, 1988 application was beino superseded and the staff's initial determination of no significant hazards consideration was for the entire application dated February 23, 1989.
8905180374 890511 PDR ADOCK 05000327 P
d 2.0 EVALUATION TVA replaced the pressure contrc1 valves in the AFWP discharge lines with cavitating venturis to improve system performance. These modifications changed the system resistance of the AFW flowpath, which necessitated redefinition of the minimum acceptable pump differential pressures for the AFWP operability
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To develop the new acceptance I
determinations required by(SR 4,7.1.2.a.in Mode 3) of the AFW system was required.
Because criteria, startup testing the units were in cold shutdown (Mode.5), TVA was unable to conduct the testing necessary to determine the SR acceptance values.
TVA submitted a startup testing plan for NRC approval by letters dated December 23, 1986, and June 25 and September 24, 1987. This plan described the general methodology to be followed in the startup test program, and requested NRC approval to enter Mode 3 in order to conduct the necessary AFW testing at the proper plant conditions. TVA's plan was approved on November 2, 1987.
Besides allowing entry into Mode 3, this approval included calculated allowable pump degradation values to be used in conjunction with SR 4.7.1.2.a until a TS change, developed from the results of the startup testing, could be approved by the staff.
The Mode 3 startup testing was performed at normal AFW system operating pressures and flows in order to determine the actual post modification system resistance.
Once the AFW piping headloss was determined, TVA determined the minimum required AFWP discharge head to establish the required flowrate. The maximum allowable pump discharge pressure degradation was determined by subtracting the minimum required head from the actual pump head.
The allowable pressure degradation was then subtracted from the nominal pump discharge pressure with the pump discharges aligned to the recirculation flowpath, which is the configuration used in the conduct of SR 4.7.1.2.a. resulting in the lowest allowable differential pressure to demonstrate AFWP operability.
l During post-modification testing in 1985, TVA discovered that AFWP 2A-A was not performing in accordance with the manufacturer's pump performance curve.
TVA replaced the impeller in AFWP 2A-A and generated a new pump perfonnance curve based on test data.
This new curve was incorporated into the calculations performed to establish the new AFWP 2A-A differential pressure criteria.
TVA performed Nuclear Engineering (NE) calculation 2219280000 based on the startup testing results for SQN Unit 2.
This calculation was submitted in TVA's letter dated May 26, 1988 as supporting documentation for the Unit 2 TS change request.
NRC staff developed concerns regarding the method used to account for test instrumentation inaccuracies in the calculation, and with the clarity of the revised TS Bases Section 3/4.7.1.2 associated with SR 4.7.1.2.a.
In response to the staff concerns, TVA reevaluated the method used to address testing instrumentation error for the Unit 2 submission, and incorporated their solutions to the NRC concerns in developing the equivalent submission for SQN Unit 1.
The revision to NE calculation 2219280000, which included SR acceptance criteria determinations for both Units 1 and 2, was included as an enclosure to r
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i
. TVA's February 23, 1989, letter requesting approval of TS change 88-24 for Unit I and 88-02 for Unit 2.
All NRC staff concerns regarding TS change 88-02 in the application dated May 26, 1988 were satisfactorily resolved'by the February 23, 1989 letter, and no new concerns were developed by the staff regarding either TS change request.
In reviewing the methodology, calculations and procedures associated with this TS change, the staff assessed TVA's engineering analysis for assurance that the AFWPs are adequate, with margin, to meet the steam generator flow and pressure requirements under worst-case conditions. The required conditions stated in the Final Safety Analysis Report (FSAR), Section 10.4.7.2, are flow of 440 gpm to the steam generators against a pressure of 1100 psia.
The new minimum AFWP differential pressures for SR 4.7.1.2.a are:
Motor Driven AFWPs:
1A-A*
1450 psid IB-B 1500 psid 2A-A 1524 psid 28-B 1464 psid Turbine Driven AFWPs:
1A-S*
1201 psid 2A-S 1180 psid The individual AFWP differential pressures tabulated above reflect the pump curves and flow paths associated with each pump.
These proposed acceptance criteria will demonstrate that the pumps will deliver at least 440 gpm, plus recirculation flow, at steam generator pressures of 1100 psia, therefore, ensuring that plant operation will remain bounded by the assumptions for AFW flow in the FSAR analyses.
The revisions made to Section 3/4.7.1.2 of the bases clarify the technical specification requirements and design bases for the AFW system.
Because the revised SR 4.7.1.2.a ensures conformance with the FSAR accident analysis assumptions, the probability or consequences of an accident previously evaluated remain unchanged.
No changes, other than those to the testing values of the AFWP, are made to the AFW system by this proposed change.
Therefore the proposed changes do not create the possibility of a new or different kind of accident from any previously analyzed.
Finally, because AFW operation remains bounded by the FSAR analysis, there is no reduction in the overall plant margin of safety.
3.0 CONCLUSION
Based on the above, the staff has concluded that TVA's calculations and engineering analysis support the proposed changes to SR 4.7.1.2.a, and Bases Section 3/4.7.1.2, of the Sequoyah TS.
The staff concludes that the TS changes numbers 88-02 and 88-04 in TVA's application dated February 23, 1989 are i
acceptable.
- 1 = Unit 1, 2 = Unit 2
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4.0 ENVIRONMENTAL CONSIDERATION
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'These amendments involve a change to a requirement with respect to the l
installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.
I The staff has determined that the amendments involve no significant increase in i
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 l
cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public coment on such finding.
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environmental assessment need be prepared in connection with the issuance of these amendments.
5.0 CONCLUSION
The Comission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (54 FR 11844) on March 22, 1989 and consulted with the State of Tennessee.
No public coments were received and the State of Tennessee did not have any comments.
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Comission's regulations, and the issuance of the amendments will not be inimical to the comon defense and security nor to the health and safety of the public.
Principal Contributor:
P. Castleman Dated: May 11, 1989 j
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