ML20067D328
| ML20067D328 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/25/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20067D312 | List: |
| References | |
| NUDOCS 9403080170 | |
| Download: ML20067D328 (7) | |
Text
/psas%,
i UNITED STATES
{.$g'c <
[$
NUCLEAR REGULATORY COMMISSION
' l WASHINGTON D.C. 20565-0001 yv...../
SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDHENT N0. 95 TO FACILITY OPERATING LICENSE N0. NPE-1 AMENDMENT NO. 79 TO FACILITY OPERATING LICENSE N0. NPF-18 COMMONWEALTH EDIS0N COMPANY LASALLE COUNTY STATION. UNIVS I AND 2 DOCKET NOS. 50-373 AND 50-374
1.0 INTRODUCTION
By letter dated January 28,1994 (Reference 1) Commonwealth Edison Company (CECO) proposed changes to the functional test interval (FTI) from the existing one-month to a three-month interval for several reactor protection system (RPS) instrumentation channels because testing may cause some RPS channels to become inoperable.
This exigent change is requested to avoid Unit 2 shutdown, due to induced inoperability of those RPS channels which could occur if those channels are functionally tested in accordance with the current FTI of the plant Technical Specification (TS). This will allow continued operation of Unit 2 for the next three-months and provide Ceco more time to find the root cause of the degraded instruments and determine the appropriate corrective action.
CECO's justification for the proposed changes is based on the previously approved topical report on the subject FTI by the NRC staff.
This submittal is part of the TS improvement project for both units of the LaSalle County Station.
2.0 EVALUATION Main steam line isolation valve (MSIV) closure, turbine stop valve (TSV) closure, turbine control valve (TCV) fast closure, and manual scram are functional units in the RPS trip system of both LaSalle Units.
The HSIV position is monitored by a limit switch that has a spring loaded arm which automatically returns to its normal position after being toggled during valve strokes.
If a limit switch arm is not in the normal position when the valve is next moved from open to close or vice-versa, the limit switch will not toggle.
For instance, when an MSIV limit switch arm fails to return to normal after being tripped during the closure of the associated MSIV, the limit switch will not be reset and the associated RPS logic relay will remain de-energized when the MSIV is reopened.
This will render the MSIV closure RPS trip inoperable and the limit switch arm will have to be manually brought to
" spring return-to-normal" position for resetting the limit switch and thereby making the HSIV closure RPS trip operable.
For an inboard MSIV limit switch, this will require containment entry and unit shutdown.
9403080170 940225 PDR ADOCK 05000373 P
o
. On January 18. 1994, during the Unit 2 shutdown, the licensee performed a functional test of the MSIV closure RPS Trip channels and observed that some limit switch arms did not automatically return to their normal position after being toggled during valve strokes.
However, before the unit start-up on January 19, 1994, the licensee verified that all MSIV limit switch arms were in the " spring return-to-normal" position and thus ensured that the MSIV closure RPS trip channels are currently operable. The licensee further stated that the plant design provides continued annunciation of a half scram if the MSIV limit switch arm does not " spring return-to-normal" position after the MSIV closure. The next functional test of these channels is currently scheduled to be performed during plant operation on February 26, 1994.
Operability of the limit switches can not be verified after this test unless Unit 2 power is reduced to less than 12 per cent (start-up mode) for containment entry.
Since the root cause of the MSIV limit switch inoperability is not yet fully understood, and any corrective action is not yet determined, the licensee has requested the TS FTI for the MSIV closure be changed from the current one-month requirement to three-months to avoid an unnecessary plant shutdown. Additionally, since the TSV closure and TCV fast closure RPS trip channels functional tests are typically performed on the same day and at the same reduced reactor power as that for the MSIV closure RPS trip channels test, the licensee has proposed similar FTI for those channels.
The licensee also proposed to change FTI for the manual scram from the current monthly to a weekly test schedule.
The General Electric (GE) Topical Report, "BWR Owner's Group Technical Specification Improvement Analysis for BWR Reactor Protection System" (Reference 2) that provided the basis for making improvements to the BWR RPS TS was submitted to NRC for approval. The analysis concluded that the current weekly and monthly FTI of the RPS channels can be extended to a quarterly schedule for both relay and solid-state plants and the FTI for manual scram from the current monthly to a weekly schedule.
The staff approved this report and several BWR licensees have changed their plant TS accordingly.
CECO's proposed changes for LaSalle Units 1 and 2 are in accordance with changes approved by the staff in the GE topical report.
In addition to referencing the GE topical report, the licensee submitted a plant specific proprietary report (Reference 1) where the BWR generic model is compared with a plant specific model. The report concluded that differences between the two models do not affect the applicability of the generic TS improvements for the LaSalle Nuclear Station, Units 1 and 2.
We agree with GE's conclusion and Ceco's proposed changes to the FTI for both Units at LaSalle Nuclear Station.
Based on our evaluation of the licensee's submittals and previous staff acceptance of the GE topical report on FTI extension for RPS instrumentation channels in BWRs, we have concluded that Ceco's proposed changes of the FTI are acceptable.
l
/
s +, o$t#
+ p * '
.,,.y,** / ~e $'
sd
<<A$I#'.#s#;#&# 3/
e
~ b [< $' / >s.+ ['
- t+;a,,:.5'$$'bih5Ysei#'$ I'h'<
s t!;<pA'
$ $+
f4
.,#f ; M" ; # $ # r' i
~~,' t g ;;,~,v s
w i!5 k $ ' i # 5' h N 'I.
- A'
'4#'#'g:gs:,3'S fs
'r ' A ti$s rd s
e s
f$'*$'%g,p.',e;s# +3 op w, *,l %; $ [ '!
e T'I*2!'i;i'}$5%fil4is
'4 i f: 4 %IS' ' i i' t;. p $ ' # ' + ',/,e p
4 Sj:t5'$+
83
- $ %$'1g'S i s xk*Mi?isk 4y#' idg
$ *I s
- /
I
.< tag :Wi#s::liN' etr$
t ds44d
$$pys:'t ggsi:sp!Wg!:!$
%$'9 e%sAgi%
- 5!!fj!$:$x4::i:i'4q
'%iti'ktili!!:E'lliS*i*
Ee:
w
!R' ii " $ >
b
'~
I
. 3.0 EXIGENT CIRCUdSTANCES Due to the problem that has developed with the LaSalle Unit 2 MSIV Limit Switches, LaSalle Unit 2 must shut down to at least the Startup mode prior to the end of the channel functional test interval to verify that the limit switches are in the " Spring Return-to-Normal" position.
The nature of the problem is that some of the limit switches may not always automatically return the limit switch arm to the normal position after being toggled during valve strokes.
If a limit switch arm is not in the normal position when the valve is next moved from open to closed or vice-versa, the limit switch will not toggle.
For the MSIV limit switches that input to the MSIV - Closure Scram RPS logic (MSIV-RPS limit switch), the problem can be readily identified.
This failure will occur when a MSIV-RPS limit switch fails to return to normal after tripping during closure of the associated MSIV (only partial closure is required to conduct the functional test). When the MSIV is reopened, the limit switch will not be reset and thus the associated RPS logic relay will remain de-energized.
If an MSIV-RPS limit switch returns to normal after being tripped, then the limit switch will reset, and thus re-energize the associated RPS logic relay. However, the limit switch may not spring return to the normal position after being reset, which is not detectable until the next time the HSIV is cycled for a surveillance.
During the time interval, an MSIV-RPS limit switch could be inoperable, unable to trip on MSIV closure.
Therefore, LaSalle Unit 2 must reduce power to less than 12% (Startup Mode) to de-inert the primary containment for entry to verify proper reset of the inboard MSIVs limit switches to assure RPS Operability.
The licensee verified by visual inspection that all MSIV limit switches were in the " Spring Return-to-Normal" position when LaSalle Unit 2 was started up on January 19, 1994, and therefore the RPS limit switches for the MSIV -
Closure Scram are currently operable.
However, the position of the MSIV limit switches would be suspect without visual observation after cycling the HSIVs.
Therefore, LaSalle Unit 2 must be shut down to at least the Startup mode in order to allow personnel access for visual verification of proper MSIV limit switch position in the " Spring Return-to-Normal" position following the functional test. The monthly channel functional test is due again at a maximum of 1.25 times the current 31-day surveillance test interval.
There are three Technical Specification Table 4.3.1.1-1 reactor protection system instrumentation surveillance requirements that the licensee typically performs on the same day, typically on the night shift (shift 1).
These surveillances meet the channel functional test requirements for item 5, Main Steam Line Isolation Valve (MSIV) - Closure; item 9, Turbine Stop Valve (TSV)
- Closure; and item 10, Turbine Control Valve (TCV) Fast Closure, Valve Trip System 011 Pressure - Low.
The channel functional tests for these valves require the valves to be cycled and a reactor power decrease to s 90% thermal power is required prior to cycling MSIVs or TCVs.
Due to the requirement to drop power and the similarity of the surveillance, these surveillance requirements are satisfied together (sequentially, not simultaneously). The E0C-RPT system instrumentation channel functional tests are also met by the same tests on the TSVs and TCVs. Therefore, although the urgency for this
amendment request is for the MSIV - Closure channel functional test, the frequencies of the TSV and TCV closure scram and E0C-RPT TSV and TCV channel functional tests are also requested to be changed to quarterly. This will minimize the number of times LaSalle Units 1 and 2 will be required to reduca thermal power to less than or equal to 90% power and keep these related surveillance together.
Without this Technical Specification amendment, LaSalle Unit 2 will need to be placed in the Startup mode to verify the proper position of MSIV limit switches for RPS instrumentation operability following performance of the above mentioned surveillance requirements.
The circumstances leading to the exigent relief request could not be avoided, because this problem with the LaSalle Unit 2 MSIV limit switches was not identified for Unit 2 startup until January 17, 1994.
The determination that LaSalle Unit 2 would be required to shut down to at least the Startup mode the next time the channel functional test for the MSIV - closure scram was due was l
not made until January 18, 1994 as a result of an operability evaluation.
The l
possibility of a change to the STI from monthly to quarterly was determined on January 19, 1994. Due to the due date of the MSIV - Closure channel functional test that must be performed by February 26, 1994 at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> (10:00 A.M. CST), the 30-day period for public comment required for a normal i
Technical Specification amendment per 10 CFR 50.91(a)(2) cannot be met.
Therefore, this request for amendment was submitted by the licensee as an exigent request per 10 CFR 50.91(a)(6).
4.0 FINAL NO SIGNIFICANT HAZARDS DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the amendment would not: (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
The staff reviewed and presented the licensee's analysis of the issue of no significant hazards consideration (provided below) and, based on that review, proposed a no significant hazards consideration in the Federal Reaistqt (59 FR 6062) on February 9, 1994.
There were no public comments in response to the notice published in the Federal Reaister.
Based on the criteria for defining a significant hazards consideration established in 10 CFR 50.92, the licensee provided its analysis of the issue of no significant hazards consideration which states that the proposed amendment will not:
Involve a significant increase in the probability or consequences of an accident previously evaluated because:
F
. The proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated. The proposed changes increase the STI for actuation instrumentation supporting RPS and E0C-RPT trip functions.
There are no changes in any of the affected systems themselves.
Because of this there is no change in the probability of occurrence of an accident or the consequences of an accident or the consequences of malfunction of equipment. With respect to the malfunction of equipment, topical reports prepared by GE demonstrated that there is a reduction in scram frequency for the RPS.
This offsets the slight increase in trip function unavailability determined by GE. This was judged acceptable by GE. The NRC concurred with this conclusion in its review of the topical reports (NEDC-30851P-A). For E0C-RPT GE demonstrated that the trip function unavailability when the surveillance interval is extended from 1 to 3 months is lower for the turbine stop valve trip function and slightly higher for the turbine control valve trip function than the same trip functions for RPS-scram. However, GE concluded that the small increase in E0C-RPT unavailability (represented by small increased risk of a MCPR violation) is offset by the benefits associated with the similar approved STI and A0T changes for the RPS-scram function.
Therefore, GE concluded that the STI changes for E0C-RPT trip function are bounded by the approved RPS analysis (Reference 3).
The NRC accepted the conclusions of GE by a SER included in Reference 4.
The proposed changes are consistent with the Safety Evaluation Reports issued in these topical reports.
The proposed changes therefore do not involve a significant increase in the probability or consequences of an accident previously evaluated.
Create the possibility of a new or different kind of accident from any accident previously evaluated because:
The proposed changes do not create the possibility for an accident or malfunction of a different type than any evaluated previously in the UFSAR.
The proposed changes increase the STI for the RPS and E0C-RPT Instrumentation.
There are no changes in the instrumentation of these systems. Since there are no such changes there is no possibility for an accident or malfunction of a different type than any previously evaluated.
Involve a significant reduction in the margin of safety because:
The proposed changes do not reduce the margin of safety as defined in the basis for any Technical Specification. The proposed changes do not change any setpoints in the above mentioned systems or their levels of redundancy.
Setpoints are based upon the drift occurring during an 18 month calibration interval. The bases in the Technical Specifications either do not discuss STI, or state "...one channel may be inoperable for brief intervals to conduct required surveillance." The proposed changes are bounded by the analyses of References 3 and 4.
These analyses, which were prepared by GE and approved by the NRC, examined the effects of extending STI and found that the proposed changes would not involve a significant reduction in a margin of safety.
LaSalle Staticn Units I and 2 RPS and E0C-RPT systems have been compared to the ger.eric analyses and verified to be bounded.
(
- The staff has completed its review of the licensee's proposed no significant hazards consideration and concludes that the amendments meet the three standards of 10 CFR 50.92(c).
Therefore, the staff has made a final determination that the proposed amendment does not involve a significant hazards consideration.
5.0 STATE CONSULTATION
In accordance with the Comission's regulations, the Illinois State official was notified of the proposed issuance of the amendments. The State official had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the 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 cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (59 FR 6062). 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 or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety 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, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
1 Principal Contributor: Iqbal Ahmed, HICB Date:
February 25, 1994
. l i
8.0 REFERENCES
l 1.
CECO Letter (Gary G. Benes) to NRC (Document Control Desk) dated January 28, 1994.
2.
General Electric Topical Report, " Technical Specification Improvement Analyses for BWR Reactor Protection System," NEDC-30851P, DRF A00-02119-A, May 1985.
3.
General Electric Topical Report, " Technical Specification Improvement l
Analyses for BWR Reactor Protection System," NEDC-30851P-A, DRF A00-02119-A, March 1988.
t j
4.
General Electric Topical Report, " Bases for Changes to Surveillance Test Intervals and Allowed Out-of-Service Times for Selected Instrumentation i
Technical Specifications", GENE-770-06-1-A, December 1992.
l l
l l