ML20079P049
| ML20079P049 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/18/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20079P047 | List: |
| References | |
| NUDOCS 9111120172 | |
| Download: ML20079P049 (4) | |
Text
_
l
/p3 Rt. %
UNITED STATES E" 3 g NUCLE AR REGULATORY COMMISSION n
3-W WAsHINoToN. D. c. 20sss
- %M e
- SAFETY EVALUATION BY THE OFFICE OF f"JCLEAR REACTOR RECULATION R1 LATED TO AMENDMENT NO. 4 TO FACILITY OPERATING LICENSE l0. NPF-87 TEXAS UTILITIES ELECTRIC COMPANY, ET AL.
COMANCHE PEAK STEAM ELECTRIC STATION, UNIT I DOCKET NO. M-445
- 1. 0 INTRODUCTION By application dated June 28, 1991, Texas Utilities Elenric Company (the licensee) requested changes to the Technical Specifications (Apperdix A to Facility Operating ticense No. NPF-87) for the Comanche Peak Steam Electric Station, Unit No. 1.
The proposed changes would revise Technical Specification Sections. 4.4.8.3.2 (a and b) and 4.5.2.r' to 1elete surveillance testing require-ments associated with the autoclosura ii.ter'ock (ACI) feature for the residual heat removal (RHR) suction isolation valves.
This change allows implementation of plant modifications to delete the ACI feature from these valves.
This proposal is being made to address the concern identified in Generic Letter 88-17, " Loss of Decay Heat Removal," about inadvertent RHK isolation events caused by purious activations of the ACI circuity.
Topicel Report LCAP-11736-A "Retidual.. eat Removal System Autoclosure Interlock Deletion Report for the Westinghouse Ow,urs Group" provides the basis for the removal of the ACI.
The Safet Evaluation Report (SER) documenting the NRC review of WCAP-11736 concluded that a net safety benefit would result from the removal of the RHR ACI provided that five plant improvements listed in the SER were implemented.
In addition, the SER concluded that the information containeo in the report may be referenced in the olant-specific submittal requesting removal of the RHR ACI.
The above mentioned plant improvements are listed below:
(1) An alarm will be added to each RHR sucticn valve which will actuate if the valve is open and the pressure is great;r than the open permissive setpoint and less than the RHR system design pressure minus the RHR pump head pressure.
( ', Valve position indication to the alarm must be provided from stem-mounted limit switches and power to these switches must not be affected by power lockout of the valve.
(3) The procedural ime
- nents cescribed in WCAP-11736 should be implemented.
Procedures themsei
. are p' ant-specific.
(4) Where feasible, power :.hould be removed from the RHR suction valves prior to their being learchecked (plant specific).
9111120172 911018 PDR A00CK 05000445 P
(S) The RHR suction valve operators should be sized so that the valves cannot be opened against full system pressure (plant specific),
2.0 EVALUATION Th'e proposed revision to Technical Specification (TS) 4.4.8.3.2 deletes the sdrveillance requirement to verify once every 31 days that one of the two in-series valves in each RHRS train is in the open position with its power removed, and to verify once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that the second suction valve in each train is open.
This is reolaced by the requirement to verify once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> that both suction valves in each train are open.
The propose' change in TS 4.5.2 deletes the surveillance requirement for verifying AC1 operability (the open permissive interlock surveillance remains unchanged).
The NRC approved report WCAP-11736 provides the underlying basis for justifying
-the licensee's planned action.
The WCAP-11736 reference plant for Comanche Peak is Callaway Unit 1.
The licensee's suomittal includes
'isting of the relevant design / operational differences that exist between Comt.5 PeuK and the reference plant in WCAP-11736.
The licensee has examined these differences to determine their impact on inter-system loss-of-coolant-accident potential, RHR system availability, low-temperature overpressure protection, and on the cone'usions reached in WCAP-11736.
In addition, the licensee has addressed each of the five improvements set forth in uur SER and listed above.
With regard tc the above mentioned five plant improvements, the licensee's submittal has pruvided the following responses:
Improvenent 1 - An alarm, both audio and visual, to alert the operators that an RHR suction isolation valve is open coincident with high RCS pressure is being added as part of the modification to remove the RHR auto-closure interlock.
The setpoint is consistent with the WCAP-11736 guidance.
Also, in accordance with WCAP-11736, the open permissive interlock (OPI) for each RHR suction valve will remain intact and unchanged.
Improveme,nt 2 - The CPSES desigr. utilizes motor switch contacts which are diverse from the limit switch contacts that provide main centrol board valve position indicotion.
The valve position input to the alarm will not be affected by pcwer lockout of the valves fhe original intent of using stem-mounted limit switches in the alarm circuit was to provide a diverse means of valve position indici: tion; the CPSES design provides this diversity.
Improvement 3 - The licensee has reviewed the CPSES operating procedures to
. determine the effect of ACI removal and has committed to make appropriate revisions.
If an alarm is received, the operators will be directed to take necessary actions to terminate the over,,ressure condition or close the open
'RHR suction valves.
RCS pressurization wi'll be stopped and the plant returned to the shutdown cooling mode if the open valves cannot be closed.
To fwther ensure alarm operability, instrument loop calibration procedures will be revised.
~
Improvement 4 - The licensee does not plan to remove power from the RHR suction /
1 solation valves prior to leak testing.
Since all RHR isolation valve leak rate testing is conducted at CPSES in Mode 5, removing power from the RHR suction valves prior to leak rate testing is not beneficial for the following reasons:
(a) Pcser removal from these valves does not improve the RHR syrtem's ability to withstand pressure transients since ovecpressure protection is provided and the RHR system is within its pressure limits.
(b) This requirement would ine ease the procedural complexity of leakrate t'esting and extend testing time thus potentially reducing the availability of that loop for decay heat removal and overpressure protection.
(c) If a failure of the operable RHR loop occurred during leak testing of the opposite loop, restoring the r.on-operable loop to operability would be delayed for restoration of power to the valves.
Improvement 5 - The licensee has stated that the RHRS suction valves potentially have the capability of opening against full RCS pressure.
However, TU Electric maintains that the low probabilities predicted for the opening of these valves, in concert with the open ptrmissive interlock, the new valve-not-closed alarm, the administrative controls, and the removal of power from the valves after they are closed and above 350 F, provide adequate protection against opening the valves at full RCS pressure.
3.0
SUMMARY
We have completed our evaluation of the licensee's submittal and have concluded that:
(a) The licensee has adequately identified differences in RHR system tcnfigura-tion and design / operational chararteristics that exist between CPSES and the reference plant.
Because tnese differences are insignificant, the analysis and conclusions presented in WCAP-11736 are directly applicable to Comanche Peak.
(b) The licensee has adequately addressed the five plant improvements and the licensee's proposed actions are identified.
For the proposed actions that differ from the five improvements listed in the SER, '.ne licensee has adequately demonstrated thr.t the proposed actions provided at least an equivalent level of safety relative to the improvements in the SER.
(c) The proposed change to TS 4.4.8.3.2 (a and b) will remove the requirement to verify that the RHR RCS suction isolation valve (RRSIV) is open with power to the valve operator removed, and wil'. change the requirement of verifying that the RRSIVs are open from once every 12. hours to once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
These changes are consistent with those specified for the reference plant in the already approved WCAP-11736.
(d) The proposed change to TS 4.5.2 d (to delete the requirement for verifying ACI cperability) is consistent with the licensee's plans to remove the ACI feature from the RHR suction isolation valves.
This change is, therefore, acceptable.
On the basis of these conclusions, we find the proposed TS changes and the proposed plan for RHR ACI removal to be acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Texas State officini was notified of the proposed issuance of the amendment.
The State officihl had no comments.
5.0 ENVIRONMENTAL CONSIDERAT10lj The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements.
The NRC staff has determined that the amendment involves no significan1 increase in the amountt, t.nd ne significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendment involves no signific; t hazards consideration, and there has been no public comment on such finding (56 FR 47243).
Accordingly, the amendment meets the eligibility criteria for rategorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.E2(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and cafety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, ano (3) the issuance of this amendment will not be inirrical to the common defense and security or to the health and safety of the public.
REFERENCES 0)
R. A. Newton, Chairman WOG, lett(r to NRC, dated April 22, 1988 (Submission of WCAP 11736).
(2)
A. Thadani (NRC) letter to R. A. Hewton, Chairman WOG, " Acceptance for Reference WCAP-11736. Rev. 0 ' Residual Heat Removal System, Auto 2
Closure Interlock (ACI) Renoval Report' in Plant Specific Submittals,"
dated August 8, I?89.
Principal Contribator:
M. Chatterton, SRXB/ DST Date:
October 18, 1991 1
--