ML20149N086
| ML20149N086 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/25/1988 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8803010167 | |
| Download: ML20149N086 (8) | |
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[G) Commonwealth Edloon Qc8 One FrW Natonal Plaza, Ch@ Enois
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Address Reply to: Poet Omco Box 767
. Chcago, Hlinois 60690 0767 Pet ruary 25, 1988 b
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Mr. A. Bert Davis Regional Administrator IILE U.S. Nuclear Regulatory Convaission Region III 6
-799 Roosevelt Road Glen Ellyn, IL 60137
Subject:
LaSalle county Station Unit 2 Request for Enforcement Discretion NRC Docket No. 50-374 Reference (a): Letter from H.R. Denton and J.M. Taylor to Regional Administrator dated February 27, 1987.
1 s
Dear Mr. Davis:
The purpose of this letter is to request temporary relief from a technical specification requirement to allow performance of a r<; quired refuel interval surveillance while continuing to operate Unit 2.
-raforcement Discretion", as discussed in Reference (a), most cloJely represents the circumstances of this request. Granting of this relief Will promote safety by preventing an unnecessary transient (shutdown) on an operating unit in 1
circumstances in which there is no safety reduction. An emergency techncial l
specification change is not appropriate as this situation is temporary and not expected to be recurring.
This relief would permit removal of both channels of an isolation i
instrument for a period longer than that specified in T.S. 3.3.2 while Since the performing the secondary containment leak rate surveillance.
secondary containment leak test requires that the Reactor Building Ventilation (VR) system be shutdown, continued operation of Unit 2 would result in high Main Steam Tunnel (MST) temperatures and subsequent unit trip due to Group I isolation (automatic closure of the main steam isolation valves). Therefore, a
commonwealth Edison must receive technical specification relief, to allow disabling of the MST temperature isolations on LaSalle Unit 2 or shutdown to i
perform the test.
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8803010167 880225 i
P D ',t ADOCK 05000374 l
P DCD 1
A.B. Davis February 25, 1988 The risk associated with the bypass of these trips was evaluated by the station in a review of the FSAR and a no significant hazards evaluation was performed. That evaluation is provided as Attachment A.
Additionally, a Probabilistic Risk Analysis (PRA) was performed earlier by Delian Corporation I
to support a technical specification change to permanently remove these trips.
l The PRA determined that the risk associated with permanent removal of these l
trips is probabilistically insignificant (less than 1.0 E-10).
Commonwealth l
l Edison submitted a technical specification amendment request on July 10, 1987,
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to eliminate the MST ambient temperature trip and the ventilation differential temperature trips (see 8xhibit A) utilizing the PRA to define the change in i
risk. This amendment is currently under consideration by the NRC, however, it l
has been indicated that the review process will not be completed by April 1, l
1988. As a result, it is necessary to request that NRC Region III consider l
granting relief from the applicable technical specifications for the duration I
of the secondary containment leak test in order to prevent the shutdown of Unit 2.
While preparing for a permanent technical specification change to remove these trips the background and regulatory requirements for these trips were investigated. Review of the design documentation provided by General Electric shows a requirement to install a leak detection system in the MST designed to alarm at 5 gpm and cause an isolation at 25 gpm. These values are similar to leak detection requirements inside the primary containment specified in Reg. Guide 1.45.
That Reg. Guide does not specifiy requirements for leak detection this stringent outside the primary containment.
In addition, Reg.
Guide 1.45 does not require automatic actions for leaks detected inside the primary containment. Based on this review, Commonwealth Edison believes that these trips are not required for plant safety in the event of a leak and, in fact, are a detriment to safety in that they isolate the reactor from the primary heat sink, thus challenging the function of high pressure ECCS systems to provide adequate core cooling.
The critical due date for completion of the secondary containment leak rate surveillance which is applicable to both units is April 1, 1988. While Unit 1 is scheduled to shutdown for a refuel outage on March 13, 1988, Uait 2 is not scheduled to shutdown until October of 1988. The secondary containment leak test is scheduled to be completed between the time of the Unit 1 shutdown (March 13, 1988) and April 1, 1988.
During the time the Reacter Building ventilation is secured the temperatures in the steam tunnel will rise above the trip setpoints. These trip setpoints which were based solely on leak detection are more than 100'F below the values for which safety equipment has been environmentally qualified.
A.B. Davis February 25, 1988 The special monitoring and logging described in Attachment B will provide suffi-cient documentation to ensure maintenance of and auditability of environmental qualification lifetimes.
Compensatory actions will be taken during the period of time that the trips are defeated to ensure that a small steam leak in the main steam tunnel will not remain undetected. These include special briefings for all shift operating personnel involved in the tests and special logs to record observa-tions. The details of these compensatory measures are provided in Attachment B.
past experience has shown that the secondary containment leak test can be completed in a four hour time period. The test is performed by:
- 1) shutting the VR system down, and determining the static building differential pressure (dp).
- 2) verifying that one standby gas treatment subsystem will draw down the secondary containment to greater than or equal to 0.25 inches of vacuum water gauge in less than or equal to 300 seconds, and
- 3) operating one standby gas treatment subsystem for one hour and maintaining greater than or equal to 0.25 inches of vacuum water gauge in the secondary containment at a flow rate not exceeding 4000 CFM 110%.
A detailed sequence of events, for the secondary containment leak test, is provided in Attachment C to this document.
Since secondary containment will be maintained at all times during the surveillance it is permissible, under Technical Specification 3/4 6.5, to perform the test with one or both units in operation. Continued operation of a unit is limited by the temperature rise in the reactor building and the main steam tunnel (MST) during the period of time the VR system is offline. With a unit at power and the VR system offline the area of greatest concern is the MST isolation for the operating unit since the temperature isolation setpoints are very close to the operating values.
Temperatures outside the primary containment in the reactor building are limited by Technical Specification 3/4.7.7 "Area Temperature Monitoring,"
which requires that the High pressure Core Spray (HPCS), Low pressure Core Spray (LPCS), Residual Heat Removal (RRR) and Reactor Core Isolation Cooling (RCIC) rooms be maintained between 50 and 150 degrees Fahrenheit. However, each of these areas within the secondary containment have their own ventilation and cooling system which will remain operable during the test and abnormal temperature increases in these areas is not anticipated.
A.B. Davis February 25, 1988 In summary, Commonwealth Edison has done a detailed evaluation of:
- the safety significance of the bypass of these trips
- the history of and the regulatory requirements for this trip function
- effects of a temperature excursion during performance of this test
- on safety equipment in the secondary containment e on safety equipment in the steam tunnel l
- actions and times necessary to perform the test safety
- compensatory actions to insure auditability of environmental qualification j
of safety-related equipment
- compensatory actions to monitor for potential steam leaks during performance of the test.
Based on the above discussion it is requested that Region III grant temporary relief from Technical Specification 3.3.2 Action Statements b and c with applicability to Table 3.3.2-1 items A.1.d and A.1.e.
The relief will be for the duration of the secondary containment leak test to prevent the need to shutdown Unit 2, prior to performing the secondary containment leak test.
The group I isolation logic will be temporarily modified to disable the MST tempera-ture trips, for the duration of the test, not to exceed a period of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
If you have any further questions regarding this matter, please direct them to this office.
Very truly yours,
'01{ dM C. M. Allen Nuclear Licensing Administrator 1m l
l Attachments l
l Exhibit A i
l cc:
M. Ring - RIII I
- p. Shemanski - NRR (w/o Exhibit A)
NRC Resident Inspector - LSCS (w/o Exhibit A)
M.C. parker - IDNS 4251K
ATTACHMENT A SIGNIFICANT HAZARDS CONSID_ERATION Commonwealth SJison has evaluated this request for Technical Specification relief and determined that it does not represent a significant hazards consideration.
Based on the criteria for defining a significant hazards consideration established in 10 CFR 50.92, operation of LaSalle County Station Units 1 and 2 in accordance with the proposed amendment will not:
1)
Involve a significant increase in the probability or consequences of an accident previously evaluated because:
Section 15.2.4 of the UFSAR provides the safety analysis for inadvertent MSIV losure. MST temperature trips are a potential cause of spurious MSIV closures therefore, by removing the temperature trips the risk of an inadve.rtent MSIV closure will be reduced.
The safety analysis for steam system break outside of the containment (UFSAR 15.6.4) assumes that a main steam line instantaneously and circum-ferentially breaks at a location downstream of the outermost isolation valve. Therefore, the analysis does not take into account the ability to detect smal.' steam leaks in the MST.
- 2) Create the possibility of a new or different kind of accident tiom any accident previously evaluated because:
The safety evaluation in Section 15.6.4 of the UFSAR does not include an analysis of small steam leaks. The only analysis is for a catastrophic failure of a main steam line which represents the envelops evaluate of steam line failures outside of the containment.
3)
Involve a significant reduction in the margin of safety because:
Analysis has shown that the decrease in the margin of safety due to removal of the MST temperature trips is insignificant. The small increase in risk to plant safety due to small steam line breaks which quickly propogate to large breaks is more than offset by the reduction in risk to plant safety posed by the challenges to plant safety systems caused by spurious MSIV closures.
The MST high temperature alarms will be retained to provide early warning for small steam leaks outside of containment.
m, i
. 1 Guidance has been provided in 51 FR 7744 (Reference (f)), for the application of standards to license change requests for determination of the existence of significant hazards considerations. This document provides examples of amendments which are and are not likely to involve significant hazards considerations. This proposed amendment does not involve a significant relaxation of the criteria used to establish safety limits, a significant relaxation of the bases for the limiting safety system settings, or a significant relaxation of the bases for the limiting conditions for operations.
Therefore, based on the guidance provided in the Federal Register and the criteria established in 10 CFR 50.92(e), the proposed change does not constitute a significant hazards consideration.
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l ATTAQ9 TENT 5 COMPENSATORY MEASURES TO BB TAKEN DtJRING THE PERFORMANCE OF THE SECONDARY CONTAI R M
-kEAK TEST WITH AN OPERATING UNIT t
1.
Shift operating personnel will be briefed prior to the test on:
Maintaining the operating unit in a stable condition for the duration a.
of the test.
i b.
the "Enforcement Descretion" and the technical specifications involved.
c.
the trips to be disabled.
d.
the procedures to be used during the performance of the test, e.
the special logs as described below, i
f.
actions to be taken in event of abnormal conditions.
2.
Special logs will be established on the operating unit to monitor the below listed parameters at half hour intervals. The special logs will be initiated 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> in advance of starting the test and will be continued until the isolation logic is restored to a normal configuration.
a.
Condenser normal makeup flow rate.
b.
Reactor building south main floor drain sump (2RF02).
(1) Sump Hi-Hi Level Alarm on panel 2PM13J window B402.
(2) Sump pump (2RF02PA/PB) run time in the radwaste control room, d
c.
Main steam tunnel ambient temperatures.
d.
Main steam line flow rates.
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3.
If it is determined that an abnormal condition exists, secondary containment testing will be terminated and the appropriate station abnormal procedures followed.
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0 ATTAQm8NT C PROPOSED SEQUENCE OF 8NENTS 70R PERPORMANCE OF THE SECONDARY CONTAINM M LEAK TEST WITH AN OPRRATING UNIT MINIMUM FTEP TIME REQ.
NO.
(MINUTES)
STEP DESCRIPTION I
1..
30.0 Install jumpers to disable the main steam tunnel (MST) ambient and differential temperature trips (LOA-VR-01).
2.
5.0 Shutdown' reactor building ventilation system (VR) for both units
[
(LOA-VR-01) LOP-VR-02, LTS-300-3).
i 3.
5.0 close VR isolation dampers-(LOP-VR-02, LTS-300-3).
4.
7.0 Allow the reactor building to establish an equilibrium dP
[
without the VR system in operation (LTS-300-3).
r 5.
4.0 Open 1(2)VG001 and start one standby gas treatment train (SBGT)
(LTS-300-3, LOP-VG-03).
t' 6.
5.0 Verify that SBGT will draw the containment pressure down to 0.25 inches of vacuum within 300 seconds (LTS-300-3).
7.
60.0 Verify that SBGT will maintain containant pressure at less than l'
or equal to 0.25 inches of vacuum for 60 minutes (LTS-300-3).
8.
15.0 Collect the final readings and make necessary calculations to f
determine if the test has passed or failed (LTS-300-3).
j 4
i 9.
4.0 Shutdown SBGT and close 1(2)VG001 (LTS-300-3, LOP-VG-02).
10.
5.0 Open the VR isolation dampers (LTS-300-3, LOP-VR-01).
11.
5.0 Restart VR system (LTS-300-3, LOA,VR-01, LOP-VR-01).
12.
15.0 Allow enough time for MST temperatures to return to normal (LOA-VR-01).
i 13.
30.0 Remove jumpers installed to defeat MST temperature trips (LDA-VR-01).
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PROCEDURE REFERENCES a
7 LOA-VR-01 Recovery From a Group IV Isolation or Spurious Trip of Reactor Building Ventilation.
LOP-VR-01 Reactor Building Ventilation System Startup.
LOP-VR-02 Reactor Building Ventilation System Shutdown.
j LOP-VG-02 Shutdown of the Standby Gas Treatment System.
LOP-VG-03 Startup of the Standby Gas Treatment System.
LTS-300-3 secondary Containment Leak Rate Test Procedure.
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