ML20073R428
| ML20073R428 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/04/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073R426 | List: |
| References | |
| NUDOCS 9106070099 | |
| Download: ML20073R428 (3) | |
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UNITED STATES 5
i NUCLEAR REGULATORY COMMISSION
$Mhf,f WASHINGTON. D.C. 20555
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SAFET) EVALUAT10fl PY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDl'ENT liO.157 TO FACILITY OPERATING LICENSE NO. NPF-3 TOLEDO EDISON COMPANY l
CENTER 10R SERVICE COMPANY AND THE CLEVELAND ELECTRIC lLLU!MNAT1!.C C(!PANY DAVIS-CESSE NUCLEAR F0KER STATION, UNIT NO. 1 DOCKET NO. 50-346 1
1
1.0 INTRODUCTION
Dy letter dated November 30, 1990, as supplemented December 19, 1990, and May 15, 1991, Toledo Edison propost.d an amendment to the Technical Specifi-t Cations for the Dtvis-Eesse Nuclear Pcver Station, Unit 1 (DBNPS).
The ptcposed change involves Technical Specifica+.;ons 3/4.3.2.2, "Instrumertc-l tico, Steam enc feedwater Rupture Control System Instrumentation." The l
st.pphentel letters simply provicco o note ized criginal and notification that a copy of the amendment application has been provided tc the State ci i
Ghic, respectively.
T ht. propcsec ctanges would increase the Stear. ard Feedwater Rupture Ccntrol System (SFrCC I:ain Steem (f1) low messure block permit setpcint f rom 700 psig tc 750 psig and increase the steam pressure setpoint where the block l
permit is automatically removed from 750 psig to 800 psig.
These changes would increase the pressure margin between the SFRCS block permit and the SFRCE FS icw pressure trip setpoint of 591.6 psig and minimize the possibi-lity of an inadvertent its icw pressure trip occurring during plant cooldown and heatup operations. These changes would also inctease the margin between the automatic block reset and the low pressure trip reset which ensures that the low pressure trips have cleared prior tc the automatic reset of the SFRCS curing plant startup operations.
l The SFRCE is an automatic system designed to detect and mitigate the effects of major upsets in the MS and Main Feedwater (MFW) systems, including MS and MFV line ruptures, Steam Generator (SG) overfeed, and a loss of Reactor Coolant System (RCS) forced circulation coolina.
The SFPCS dttects these ever.ts through sensing and logic channels and mit.igates their consequences by automatically positioning valves in the MS, FPW, and Auxiliary Feedwater ( AFW) systems with appropriate actuation signals dependent upon the initiating event.
l 9106070099 910604 PDR ADOCR 05000346 P
. An PS low pressure trip of an Actuation Channel of SFRCS during plant operation would be indicative of a main steam line break (ftSLB).
The MS low trip instrumentation includes pressure switches for all four SFRCS logic channels on each MS header.
An SFRCS Actuation Channel trip would cause the complete isolation of the SG connected to the MS header experiencing the trip signal, the realignment of the affected SG's AFW pump to the opposite SG, and the initiation of AFW to the unaffected SG.
It would also cicse the main steam line isolation valve and selected main feedwater valves ot-the unaffected SG.
2.0 EVALUATION By raising tte blott pettit setpoint to 750 psig, the RCS temperature at which the PS low pressure instrumentation can be blocked is increesed frou approximately 506 F to 514*F.
This represents an increase of 8*F in the range of FCS temperatures in Mode 3 where the VS low pressure instrunentation would be unavailable during couldovn operatier.s.
The FCS temperatures f ror.
506 F to 514'F represent a range of transierM plunt operations in Mode 3 end do not represent temperatures in Fede 3 where the RCS would be
. stabilized for any long periods of time. Using a nctiral ccoldown rate of 15 F/hr., the raising of the block perr.it value to 750 psig would increose by appre>imately 30 minutes the period o' tire in Mode 3 where the US low pressure instrumentation woulc be unavailable during the normal plant cooldown operation.
The increased time period over the life of the plant is so short that the probability that an PSLB would occur in this short time period is extrertly low.
Ly raising the cutomatic reset pressure of the block to 800 psig f rca 7M psig, the dead band associated with the resetting of the low pressere tru switches will not overlap the automatic reset of the block switches.
Based on past surveillanct tests of the block permit pressure switches, the switches typically reset within 20-30 ps1 above the Llock pertit setpoint.
Consequently, the 50 psi difference between the block peruit setpoint enc autcmatic reset point specified by Technical Specifications is considered to be an appropriate pressure range for the equipment in use.
By raising the automatic reset value to 800 psig, the RCS temperature at which the block automatically resets is increased f rom approximately 514' to approximttely 520 F.
This increases by C*F the range of RCS teuperature in Mode 3 where MS low pressure instrumentation would be unavailable during neatup operations.
However, it still ensures that the automatic reset occurs before the plant enters Mode 2, since per TS 3.1.1.4, " Reactivity Centrol Systems, Minimum Temperature for Criticality," the plant is not allowed to go critical until RCS Tavg is greater than or equal to 525*F.
Using a norainal heat-up rate of 15 F/hr., this temperature increase of 6'F would increase the tirae pericd during heatup where the PS low pressure instrumentation is blerked by approximately 30 minutes.
As with the increased time pericd ass :iated with plant cooldown operations, this time period over the l-
pl nt is so shu t that the probability of an
+
MSLB during this t
'es
< extremely low.
.. -.. -. ~. -
..Since normal plant operation is in Modes 1 and 2 where the MS line pressure is typically 870 psig, the raising of the block permit pressure to 750 psig and the automatic reset to 800 psig will have_ no impact. Use of the block permit in Modes 1 and 2 is not possible due to the large difference in pressure between its setpoint and normal MS operating pressure.
Consequently, the protection against MSLBs during power operation provided by the MS low pressure instrumentation-is unaffected by the proposed change.
By raising the block permit value to 750 psig and raising the automatic reset setpoint to 800 psig, the time period is increased during ccoldown and heatup where the MS low pressure instrumentation is blocked.
This increased time period is approximately 30 minutes.
As discussed above, this time period is so short that the probability of an MSLB during this interval is extremely low.
From its review of the above information, the NRC staff finds that the proposed changes to Technical Specifications 3/4.3.2.2 are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Ohio State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
This 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 or changes a surveillance requirement. The staff has determined that the amendment involves no significant increase in the omounts, anc__nc 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 significant hazards consideration and there has been no public comment on such finding.
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.2?(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 the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safet not be endangered by operation in the proposed manner, (2) y of the public will such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal-Contributor:
S. Rhow, ICSB Date:
June 4, 1991
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