ML20024H545
| ML20024H545 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/17/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20024H542 | List: |
| References | |
| GL-84-15, NUDOCS 9106040434 | |
| Download: ML20024H545 (12) | |
Text
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NUCLEAR REGULATORY COMMISSION y
WASHINGTON, D_ C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.123 TO FACILITY OPERATING LICENSE NO. OPR-39 AND AMEMDMENT NO.112 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDIS0N COMPANY ZION NUCLEAP POWER STATION, UNITS 1 AND 2 DOCKET HOS. 50-295 AND 50-304
1.0 INTRODUCTION
By letter dated March 27, 1991, as supplemented April 30, 1991, Connonwealth Edison requested a change to the Technical Specifications (TS), Section 3.5, Containment Spray; Section 3.8, Emergency Core Cooling and Core Cooling Support; Section 3.15, Auxiliary Electrical Power System; Section 6.6.3.B, Special Reports; and removal of item B.6 of the Confirmatory Order of February 29, 1980, at Zion Station, Units 1 and 2.
The purpose of this license amendment request is to reduce the number of diesel generator startups required to satisfy the diesel surveillance testing under the Confirmatory Order by incorporating the recommendations of NRC Generic Letter (GL) 84-15 and the Westinghouse Standardized Technical Specifications In addition, this amendment requests that the diesel (WSTS), Revision 4 generator testing requirements of the Confirmatory Order, Item E.6 be transferred to the Zion TS, thus deleting item B.6 from the Confirmatory Order of February 29, 1980. The April 30, 1991, letter provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 EVALUATION The staff has reviewed the proposed TS changes for Zion Station, Units 1 Our evaluation of each proposed TS change is as follows:
and 2.
Surveillance Requirement (SR) 4.15.1.B.2 and Diesel Generator Test 2.1 Schedule Table 4.15-2, ano Deletion of Item B.6 from the Confirmatory Order of February 29, 1980 The licensee has proposed SR 4.15.1.B.2 which incorporates the requirements 29, 1980.
Item B.6 of item B.6 of the Zion Confirmatory Order of February requires periodic testing of the diesel generators per Regulatory Guide (RG) 1.108, Revision 1, " Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants," Auaust 1977. Further, it requiresthatavariableallowableoutagetime(A0T)beappliedbeyondwhat is stipulated in the limiting condition for operation (LCO).
By incorporating item B.6 into the Zion TS, the licensee proposes to delete it (Item B 6 of Appendix A, page 3) from the Confirmatory Order. The proposed SR 4.15.1.B.2 1
9106040434 910517 DR ADOCK 0500 5
includes a diesel generator test schedule, Table 4.15-2, similar to, but a modified diesel generator test intervel as required under the Confirmatory Order. Table 4.15-2 in the proposed SR 4.15.1.B.2 incorporates a revised test frequency of the diesel generator which is based on:
a.
A per diesel basis instead of the per unit basis that is currently required, b.
The number of f ailures in the past 20 valid starts on a per diesel basis rather than the current testing frequency on the number of failures experienced in the last 100 valid tests per nuclear unit, c.
Failures resulting from the starting air compressor and the oil transfer pump and other failures discovered during the manufacturer's inspection do not constitute failure of a valid test, and do not require an increased frequency of testing.
The licensee contends that:
a.
Testing of a redundant diesel based on failures experienced on another diesel is excessive since this imposes additional stress and wear on the other diesels that are good performers.
Such unnecessary testing could adversely affect the continued performance and reliability of the other diesels. Thus, the per diesal test concept reduces the number of unnecessary diesel starts and eliminates repetitive testing of the diesels that are good performers.
By identifying poor performing diesels, the licensee can concentrate on corrective actions to enhance and maintain diesel reliability of those diesels, b.
The diesel generator test frequency, based on the number of failures in the past 20 valid starts cn a per diesel generator basis, takes into consideration the poor performers by requiring them to be tested more frequently (every 7 days). Once the operability of the poor performing diesel has been demonstrated to a-satisfactory level (performante of seven consecutive failure free tests and number of f ailures in last 20 demands is reduced to one), the testing frequency can return to normal (every 31 days),
c.
If the diesel testing failure is contributed to by a failure of certain redundant equipment such as air start compressor or oil transfer pump and provides direct evidence that a diesel generator would start and perform its design function when required, such failures of a valid test should not result in an increased frequency of testing.
We have reviewed the licensee's proposed SR 4.15.1.B.2 and diesel generator test schedule Table 4.15-2.
We find that SR 4.15.1.B.2 incorporates the basic intent of item B 6 of the Confirmatory Order since the diesel test
. frequency is consistent with the recommendation of GL 84-15 and criteria for determining the number of failures and number of valid tests remains consistent with RG 1.108, Revision 1.
Furthermore, by replacing the Confirmatory Order requirements with SR 4.15.1.B.2 and Table 4.15-2 of the Zion TS, we also find that it is no longer necessary for item B.6 to be required by the Confirmatory Order.
Based on the above, we conclude that the proposed SR 4.15.1.B.2, Table 4.15-2, 6nd rescission of item B.6 of Appendix A, page 3 (Confirmatory Order of February 29, 1980) are acceptable.
2.2 Surveillance Requirement (SR) 4.15.1.B.3 The diesel generatur testing recuirements under item B.6 of the Confirmatory Crder does not apply during the ref ueling outage. The licensee intends to transfer this portion of *he Confirmatory Order requirements of item B.6 to the Zion TS.
We reviewed the oroposed SR 4.15.1.B.3 where the diesel generatur testing during refueling outage will be perf ort co ir, accordance with RG 1.108, Revision 1, but does not contain the testing frequency specified per Table 4.15-2.
As proposed, the licensee is required to test the diesels only once during the refueling period (typically 13 weeks) and failures encountered during this period do not affect test frequency of diesels.
In the staff's view, the proposed change deviates f rom a normal 31-cay test interval prescribed for diesel testing under GL 84-15.
Further, Zion Staticn has no TS requirements regarding the number of offsite sources and diesels that should be available during a refueling outage or shutdown.
Based on the above, we find that the proposed SR 4.15.1.B.3 is unacceptable.
However, by letter dated April 30, 1991, the licensee has committed to establish administrative controls which will maintain one diesel generator operable, and perform diesel testing per Table 4.15-2 during a refueling outage. The formal amendment change will be submitted at a later date. On this basis, we conclude that the proposed SR 4.15.1.B.3 would be acceptable.
I.3 Surveillance Requirements (SRs) 4.15.1.B.2.a. b, c and Bases 4.15 The licensee proposes to delete "Following the completion of the initial testing program specified in 4.15.1. A.1" from SR 4.15.1.B.2.a which relates to completion of the initial diesel generator testing program.
Since the initial testing program has been completed, the licensee has determined that this phrase is no longer valid or needed.
The licensee also proposes to delete the words "each month" or " monthly" in SRs 4.15.1.B.2.a. b, c and to revise the Bases for diesel generators, Section 4.15, to reflect newly approved Sks 4.15.1.B.2 and 4.15.1.B.3.
4 We agree with the licensee that the monthly diesel generator testing is no longer applicable as the diesel testing frequency has been modified per Table 4.15-2 and therefore, the above deletions are acceptable.
In order to be consistent with the proposed changes to SRs 4.15.1.B.2 and 4.15.1.B.3, the licensee proposes to reflect the above changes to Section 4.15, and to delete the (omma after " diesel" of " tests are also performed on the diesel," in the seconi senter,ct oi the secor a paragraph of the Cases, Section 4.15.
We have reviewed the revis"d Bases Section 4.15 and find them to be consistent with the proposed cb6nges to SR 4.15.1.B.2 and 4.15.1.B.3.
The revisions to the Bases Section 4.15 are acceptable.
2.4 Surveillance Lecuirement (SR) 4.15.1.B.3.b The propcsed Sh 4.15.1.B.3.b is to provide an allowance fcr the common diesel (0) to be tested no more than once per refueling outage frequency for a given unit rather than during the refueling outage of each unit.
The licensee states that if the conron diesel generator can be demonstrated to be capable of running loaded on one unit, then it will satisfy the same test requirements for the other unit since it is loaded and tested in an identical manner. Therefore, it is not necessary to subject the common diesel generator to the same test during refueling f or each unit.
Based on the above, we conclude that the proposed change is consistent with the intent of GL 84-15 to reduce the number of unnecessary tests on the diesel generators and, therefore, the additior, of SR 4.15.1.B.3.b is acceptable.
2.5 Surveillance Reauirement (SP) a.15.1.B.5 The licensee proposes to add a special report as SR 4.15.1.B.5, which will be required to supply diesel generator reliability information for all valid and non-valid diese' generator failures.
If the number of failures (on a per diesel generator basis) in the last 20/100 valid tests is greater than or equal to 7, the report shal; also include the additional information recommended in regulatory position C.3.b of RG 1.108, Revision 1.
We find the addition of this reporting requirement to be consistent with GL 84-15 and the WSTS and is conservat've since the current Zion TS has no such reporting requirements. We conclude that the proposed special report as SR 4.15.1.B.5 is acceptable.
2.5 Action Statement (AS) 3.15.2.A and Surveillance Requirement (SR) 4.15.2.A With or,e of the required of f site power sources inoperable, the licensee proposes to change AS 3.15.2.A and SR 4.15.2.A to:
(1) require a 72-hour allowed outage time (A0T) versus the current 48-hour A0T, (2) require testing of l
L--
, diesel generators once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> versus once each day, and (3) add demonstration of the operability of the remaining offsite power source within I hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereaf ter.
It also proposes to remove the word " monthly" from SR 4.15.2.A.
The licensee states that increasing the A0T from 4P hours to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for an inoperable offsite power source will have minimum undesirable plant transients and reduce the number of forced plant shutdowns due to an inoperable offsite power source.
The licensee cor.tends that when one of the required sources of offsite power is inoperable, sufficient offsite power is available from the other required offsite power source and the redundant standby diesel generators to ensure that the unit can be shut down and maintained in a safe shutdown condition following a design basis transient or accident.
To ensure that a reliable offsite power source remains, the availability of thc remaining required offsite power source will be verified on a more frequent basis (i.e.,
within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter)._ The licensee also states that the proposed diesel testing, once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, is consistent with the GL 84-15 recommendation for minimizing unnecessary stress and wear on de diesels.
We have reviewed the proposed A0T increase from 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for an inoperable of fsite power source in AS 3.15.2. A and SR 4.15.2. A and find that the 72-hour A0T is consistent with RG 1.93, " Availability of Electric Power Sources," December 1974, Regulatory Position C.1 and with the requirements of the WSTS, Pevision 4 We also find that the word " monthly" testir:g no longer applies in SR 4.15.2. A since the diesel generators will be tested according tc itble 4.15-2.
Therefore, we conclude the proposed changes to AS 3.15.2. A and SR 4.15.2.A are acceptable.
2.7 Surveillance Requirement (SRI 4.15.2.B The licensee has proposed to change the word ' synchronized" to " loaded" in SR 4.15.2.B during the total loss of offsite pcwer condition.
The current SR 4.15.2.8 wording implies that the methods of loading the diesels are through synchronization only during the total loss of offsite power conditior.. The prcposed chge clarifies the metbcd of transferring loads to the diestl generator either as a dead bus transfer or synchronizatier.. We find the proposed change in SR 4.15.2.B acceptable.
2.8 Action Statement (AS) 3.15.2.C and Bases 3.15 This AS proposes to allow continued operation of a unit with one diesel generator inoperable only during the succeeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, rather than during the succeeding 7 days as presently allowed.
In addition, a footnote has been added to allow the common (0) diesel generator to be inoperable for up to 7 days for maintenance and testing providtd one unit is in Mode 5 or 6 (i.e., cold shutdown or refueling) and at least three remaining d.esels are operable (i.e., two operable on the operating unit and one operable on the unit in Modes 5 or 6).
The licensee also proposes to reflect the above changes in the Bases Section 3.15.
. Although current AS permits continued operation of a unit with one diesel inoperable for a period of 7 days, this requirement has been superseded by item B.6 of the Confirmatory Order which st',. lates a reduced A0T schedule based on the number of diesel f ailures on a unit (e.g., 7-day A0T for less than four f ailures, 32-hour A0T for four f ailures, 8-hour A0T for five f ailures, and 0-hour A0T for six or more failures).
The licensee feels that these time restrictions are often counter productive for maintenance activities that are needed to enhance the operability and availability of the diesel generators. Therefore, the proposed AS incorporates a 72-hour A0T which-is independent of the number of diesel failures. The licensee contends that this is conservative when compared to the 7-day A0T currently required in the Zion TS, We have reviewed the licensee's proposed request for the AS and find that the reduction of A0T frora the current 7 days to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for one inoperable diesel is conservative because:
a.
Less time (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> versus 7 days) is now available to allow one diesel to be inoperable before requirine the unit to shut down, but it allows the use of the full 72-hour A0T regardless of the number of diesel generator failures, b.
A maximum of two operability tests will be required for the 72-hour A0T as compared to the 7-day A0T, which requires up to a total of 14 diesel operability tests (i.e., 2x7).
The proposed change from 7-day A0T to 72-hour A0T is consistent with the intent of GL 84-15 for reducing the number of unnecessary diesel starts to minimize undue wear and stress on the diesels.
With regard to the footnote to allcw the common (0) ciesel generator to be incperable for up to 7 days, the licensee contends that under the existirg TS, the cctrmon (0) diesel which serves both operating units, is required to be operable whenever either unit is in operation and it is required to maintain high diesel reliability. Therefore, the 7-day period is needed to support the current station preventive maintenance program which involves extensive inspection / maintenance during each refueling outage.
On this basis, the preventive maintenance pregram for the common diesel generator has been divided into two separate work packages where each package takes approximately 7 days, i.e., Unit 1 program package deals with fuel oil system while the Unit 2 program package deals with the %be oil system.
In addition, the licensee feels that the proposed footnote of AS 3.15.2.C which allows a 7-day inoperable period for the common diesel is "not nonconservative " This is because a 7-day A0T exists currently in the Zion TS for the common diesel on the operating
)
unit and it is also consistent with the operating A0Ts for the service water and component cooling water systems.
I In addition, the licensee has committed to take the following compensatory measures during the 7-day period when the common diesel is inoperable:
1
, a.
One unit must be in Mode 5 or 6, verifying that at least the three remaining diesel generators are operable by performing SR 4.15.1.B.2 within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to removal of the common diesel from service and verifying that at least three service water pumps and three component cooling water pumps are operable with their associated emergency power
- supplies, b.
The three remaining operable diesels will be verified for their operability daily per SR 4.15.B.2, and for the unit in Mode 5 or 6, no mid-loop or reduced inventory operations, as defined in GL 88-l'/, " Loss of Decay Heat Removal" will be performed while there is fuel in the vessel, c.
Should one or more diesels for the operating unit become inoperable, the operating unit would be brought to Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 5 within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
d.
Should the twc dedicated diesels on the unit in Mode 5 or 6 become inoperable, the operating unit will enter AS 3.15.2.C and 3.0.5.
We have reviewed the scope of preventive maintenance activities for the common diesel in both work packages and their corresponding expected completion time for each task. We have also considered the fact that unforeseen problems may necessitate work package and/or procedure changes to be performed requiring additional time, and as well as the difficulty in the performance of simultaneous work packages because of the limited diesel room size.
Based upon the above consideration, we agree with the licensee that the 7-day A0T for the common (0) diesel generator is needed to ensure that adequate time is available to properly perform at least one-half of all the necessary refueling outage maintenance and surveillance testing activities.
The licensee also has included a discussion on the proposed footnote of AS 3.15.2.C and how it affects the other emergency core cooling system (ECCS) equipment AS in the Bases Section 3.15 of the TS, and proposed to relocate several paragraphs (no content change) to a new page.
We find then to be consistent and acceptable.
Based on our review of the above changes, we conclude that the proposed AS 3.15.2.C, the footnote regarding an inoperable common (0) diesel generator, and the Bases, Section 3.15 are acceptable.
2.9 Action Statement (AS) 3.15.2.C and Surveillance Requirement (SR) 4.15.2.C The present AS 3.15.2.C and SR 4.15.2.C require demonstrating the operability of the remaining diesel generators immediately and daily thereaf ter when a diesel is found to be inoperable. The licensee proposes to modify AS 3.15.2.C and SR 4.15.2.C to include demonstrating the operability of the remaining diesels once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per SR 4.15.1.B.2 instead of daily, as currently required. Additionally, the proposed change will also include the demonstration of the availability of two offs',te power sources within I hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter following the loss of one diesel.
8 The reason for diesel operability test following the loss of one diesel is to ensure that the rer.oining diesels will be operable as designed and are not experiencing a common mode failure.
By testing the diesels once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the licensee feels that it provides timely and adequate assurance of operability of the remaining diesels since the last required surveillance tests.
The licensee further states that the 24-hour testing requirement conforms with GL 84-15, which is intended to reduce the number of unnecessary test starts on the diesels for reducing undue wear and stress on the diesels.
We have reviewed the proposed AS 3.15.2.C and SR 4.15.2.C and find that the diesel operability test, once within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> requirement when a diesel is found to be inoperable, is consistent with GL 84-15.
In fact, we recommended similar changes to the WSTS requiring one test within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following the loss of one diesel. We have also reviewed the proposed revision of AS 3.15.2.C and SR 4.15.2.C to include demonstrating the availability of the two offsite power sources by performing SR 4.15.1.A within I hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter. We find that this change is consistent with the WSTS.
We conclude that the proposed changes to AS 3.15.2.C and SR 4.15.2.C are acceptable.
2.10 Deletion of The Following Items (Notes, Table, Asterisk "*" and Associated Footnotes)
The licensee proposes to delete the following items from the TS as they are no longer applicable or needed since the time limitation for atendments use has expired.
They are:
a.
Note on page 255a concerning one time use of " Diesel Generator "0" 45 Day Outage Period" (1989),
b.
Table on page 225b concerning one time use of " Action Statement for 45 Day Period of "0" DG Outage" (1989).
c.
Surveillance Pequirement 4.15.1.B.1 on page 256 concerning one time use of initial diesel generator testing program (1975).
d.
Asterisk "*" and associated footnote on page 260 concerning one time use of reserve AC off site power source ( AS 3.15.1.C.1) for Unit 1 (19EI).
e.
Asterisk "*" and associated footnote on page :EE concerning one tine use of battery charger cross-tie breakers ( AS 3.15.2.F) (1987).
f.
Asterisk "*" and associated f ootnote on page 267 concerning minimum fuel supply (25,000 gallons) in the fuel tanks during initial plant startup.
=e
?
4 g.
Sentence concerning the above 25,000 minimum gallons fuel supply for the diesel qualification test program on page 273 to reflect in the Bases Section and change the word " diesel fuel supply" to " diesel fuel storage."
h.
Asterisk "*" and associated footnote on page 165 concerning one time use of the IB charging pump (AS 3.8.1.C) (1982).
We have reviewed the above deletions from the TS. We agree with the licensee that the above deletions and removals from the TS are justified and are acceptable.
2.11 Deletion of Additional Diesel Generator Testings for an Inoperable ECCS Components from the following Surveillance Requiremer.ts (SRs)
For inoperable ECCS components, the revisions to the following SRs are proposed to require testing of the remaining redundant ECCS components only, and not the associated standby power supplies (i.e., diesel generators),
a.
SR 4.6.1.C for one inoperable containment spray pump system on page 151.
b.
SR 4.8.1.C for one inoperable centrifugal charging pump system on page 165, c.
SR 4.8.2.C for one inoperable safety injection pump system on page 169.
d.
SR 4.8.3.C for one inoperable residual heat removal pump system on page 172.
e.
SR 4.8.6.C for two inoperable component cooling water pumps on page 176.
f.
SR a.8.7.C for one inoperable service water pump on page 179.
g.
Bases 3.8/4.8, ECCS and ECCS Support Systems on page 194 The licensee stated that the NRC, under GL 84-15, eliminated diesel generator testing when ECCS systems are declared inoperable for some of the earlier operating plants.
Since Zion is one of the older plants which required additional diesel testings should an ECCS component become inoperable, the licensee has proposed to demonstrate the operability of the remaining ECCS j
systems only and not the associated diesel generators.
l We have reviewed the licensee's proposed deletions of the standby power supplies for the remaining ECCS systems and find that it agrees with the intent of GL l
84-15 and the current WSTS.
Therefore, we conclude that the proposed deletion i
of diesel testings f rom SRs 4.6.1.C, 4.8.1.C, 4.8.2.C, 4.8.3.C, 4.8.6.C and 4.8.7.C, and revision to Bases 3.8/4.8, ECCS, and ECCS supporting systems are l
acceptable.
r 4 '
2.12 Administrative Section 6.6.3.B, Special Report Since proposed SR 4.15.B.5 requires reporting of all diesel generator failures to the Commission within 30 days, the licensee has proposed to revise administrative Section 6.6.3.B to add the requirement to prepare a Special Report when required per SR 4.15.1.B.5.
We find the proposed change to be acceptable.
3.0 EVALUATION OF SUPPORTING PROBABILISTIC RISK ANALYSIS The licensee's probabilistic risk analysis is documented in the report WCAP-12873, "Probabilistic Risk Analysis of Changes in Diesel Generator Test P?quirements for Commonwealth Edison Company Zion Station Units 1 and 2," Westinghouse Electric Corporation, February 1991.
It focuses on the effects of the proposed changes on the unavailability due to maintenance and on the failure rates of the diesel generators. The analysis makes use of the system models and risk models in the Zion's living probabilistic risk assessment (PRA) which is documented in the report, " Zion Living PRA," Westinghouse Electric Corporation, updated August 26, 1987.
A complete description of the PRA models is given in the Zion Probabilistic Safety Study, Commonwealth Idison Company, dated 1981.
The analysis uses the plant operational data from the Zion, Byron, and Braidwood Nuclear Power Stations, including the engine maintenance reports, diesel generator deviation reports, diesel generator start /stop logs, limiting conditions for operation action reports, and NUREG-0200 Monthly Status Operating Reports, covering the period from 1983 to 1990.
The emergency diesel generators in these three nuclear power plants have the similar designs, the same manufacturer, and the similar maintenance requirements.
On the besis of the maintenance data at the Zion and Braidwood stations, the licensee projects in the analysis that it is feasible to reduce the maintenance duration for the unit-dedicated diesel generators that will be compatible with the proposed TS changes.
For the common diesel generator, the maintenance unavailability is conservatively assumed to be unchanged with the proposed TS amendment. The failure rates for both the unit-dedicated and the common diesel generators are also projected to remain unchanged after the proposed TS changes are implemented.
l-The analysis provides a sensitivity study to determine the effects of various assumptions of maintenance unavailability and failure rates of the diesel generators on the reactor core damage frequency, including the case of the proposed TS changes. The computed increases in the reactor core damage frequency, in the seven cases of the sensitivity study, are all less than ten percent of the base case which is based on the Zion Living Probabilistic Risk Assessment I
of the current TS.
l
l
' The Zion Probabilistic Safety Study has been reviewed by the Sandia National Laboratory, under contract to the NRC, and documented in report NUP,EG/CR-3300, "Peview and Evaluation of the Zion Probabilistic Safety Study," Volume 1, May 1984 The Sandia report indicates that the init'ating events covered in the Zion Probabilistic Safety Study "seem to be relatively complete in comparison with other PRAs," and that the fault trees " appear to be complete and correct." The report concludes that the systems analysis of the Zion study is consistent in scope and detail with other probabilistic risk assessments.
The report notes that the lion analysis of the emergency diesel generator system is appropriate, and the overall result appears reasonable compared with the overall results of other studies.
The staff has determined that the assumptions used in the licensee's risk analysis are reasonable and conservative in that the maintenance unavailability is projected to be reduced for the unit-dedicated generators but unchanged for the common generator.
The plant operational data that were used in the analysit cover a reasontble period of time anc are appropriote for the analysis (i.e., use of the data in the diesel generator start /stop log sheets, diesel generator deviation reports, limiting conditions for operation action reports, and NUREG-0200 Monthly Status Operating Reports from 1983 to 1990 at the Zion, Byron and Braidwood stations),
in addition, the staff has determined that the NRC contractor's review of the licensee's probabilistic safety study is compre-htnsive in that, every event tree and f ault tree in the Zion Probabilistic Safety Study has been examined f or accuracy and cor.pleteness.
Comparisons with other probabilistic risk assessments are also made in the Sandia's report.
Dr. tLe t' asis of the atuvt. p aluation, the staff concludes it.ot the licentee's probabliistic risk analysis cf the proposed TS changes of the surveillance anu tu t tequirements for the emergency diesel generators bt the Zion Nuclear Power Station, Units 1 and 2, is acceptable.
4.0 STATE CONSULTATION
In accordonce wi+h the Comnission's regulaticos, the Illinois State officiel was notified of the proposed issuerte of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a f acility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance req >irements.
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 (56 FR 11492).
Accordingly, the
a 10 amendt.ents 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 6ssessment need be prepaied in connection with the issuance of the amendments.
6.0 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 Conmission'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.
Principal Contributor:
Peter Lang Date:
May 17, 1991
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