ML20197B515
| ML20197B515 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 10/23/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20197B491 | List: |
| References | |
| GL-84-15, TAC-55863, NUDOCS 8610300317 | |
| Download: ML20197B515 (7) | |
Text
a ENCLOSURE 1 UNITED STATES
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SAFETY EVALUATION OF REVISED TECHNICAL SPECIFICATIONS FOR DIESEL GENERATOR TESTING GRAND GULF NUCLEAR STATION UNIT 1 DOCKET NO. 50-416
1.0 INTRODUCTION
The Mississippi Power and Light (MP&L) Company proposed changes to the Technical Specification concerning diesel generator testing for Grand Gulf Unit 1 by letter May 22, 1986. Some of the changes are in response to Generic Letter 84-15, some changes are proposed to meet the intent of Generic Letter 84-15 to reduce unnecessary diesel generator testing, and other changes are proposed to clarify present requirements.
The objective of diesel generator periodical surveillance testing is to meet the reliability goals of Regulatory Guide 1.108 for the diesel generators.
Such surveillance testing provides a degree of assurance of the availability of the diesel generators in mitigating various transients and postulated events Therefore, the existing DG testing concept following a loss of offsite power.
is that the above assurance has to be demonstrated with more frequent testing Thus, Standard Technical Specifications as the number of failure increases.
require that the DGs be tested in accordance with Regulatory Guide 1.108 whe Furthermore, the the test interval depends on the demonstrated DG perfomance.
test interval is established conservatively on a per nuclear unit basis rather than on a per diesel generator basis. The proposed changes to the Technical Specification regarding the diesel generator testing consist of (1) reducing the number of " fast cold" starts, (ii) eliminating excessive testing, (iii) alleviating the frequency of certain testing which may have a potential for degradation of the DG and (iv) modifying the test interval basis on failures per diesel generator unit rather than per nuclear unit.
2.0 EVALUATION MP&L has proposed the changes to Technical Specifications to accomplish its The ste'f has for sometime been objective to reduce diesel generator testing. evaluating the freque The staff degradation of engine parts due to frequent cold fast start l
The licensee was also potential without affecting the overall DG reliability.
encouraged to propose TS changes in additional areas identified below to redu These changes are made as an interim action on DG excessive DG testing.
testing prior to final resolution of Generic Issue B-56, and are consistent with Generic Letter 84-15 guidelines.
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Reduced testing of diesel generators from every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to once within 24 (1) hours when a diesel generator or offsite line is inoperable.
Testing of DGs based on the number of failures en a per diesel generator (2) basis rather than unnecessarily testing all diesel generators.
i Reduced test frequency for an individual diesel generator based on the number of failures from the present minimum interval of every three days (3) to a minimum of seven days.
The staff has reviewed the proposed changes to determine whether these changes The results of our review are as are in line with the above guidelines.
follows:
TS 3/4.8.1, A.C. Sources, ACTION a and b:
1.
Present TS ACTION a Statement "With either one offsite circuit or die generator 11 or 12," is divided into the two Action Statements, which are ACTION a," With one offsite circuit," and ACTION b, "With either generator 11 or 12".
diesel generator of the above required A.C. electric power sources'has not bee successfully tested within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to entry into inoperable due to any cause other than preplanned preventative maintenance or testing and the remaining diesel generator has not been successfully tested within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to entry into this ACTION Statement."
The objective of the acti_on statement in the existing Technical Specifications is to demonstrate the imediate operability of the remaining A.C. electrical j
sources by performing Surveillance Requirement whenever one offsite circuit either diesel generator 11 or 12 of the required A.C. electr cperability prior to entry into this ACTION Statement inoperable.
The of the remaining A.C. power sources after entry into ACTION Statement.
staff concludes that these additional sentences of the ACTION Sta not in accordance with the intent of Standard Technical Specifications and th guidelines provided in GL 84-15 as indicated above and are, therefore, not acceptable.
The remainder of the ACTION a and b statements are in accord above guideline and therefore are acceptable.
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ACTION c:
The time requirement for testing the remaining two operable diesel generators The proposed is presently within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-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.
change will require testing of the operable diesel generators pursuant to This change is Specification 4.8.1.1.2.a.4 only once within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. consisten f
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! The last sentence of present ACTION b has been deleted with proposed ACTION c The deletion of the restoration statement for two offsite circuits and diesel generators 11 and 12 within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is purely administrative and is changes.
proposed only for clarification and therefore the proposed change to delete the last sentence of present Action b is acceptable.
3.
ACTION d:
The only change to ACTION d is editorial in nature due to the proposed The renumbering of the Action Statements and the addition of new ACTION 1.
additional ACTION i is not acceptable as evaluated below and therefore refer-ence to ACTION a or b should be changed to ACTION b or c as applicable.
4.
ACTION e:
Present test requirements for diesel generators 11, 12 and 13 with two of the required offsite circuits inoperable are to perform 4.8.1.1.2 a.4 for one diesel generator at a time, within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and at least once pe thereafter.
The proposed change complies with the above performed once within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. guidelines to reduce excessive diesel gen acceptable.
The restoration requirement of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for both of the inoperable offsite circuits is deleted from the current ACTION d and not included in proposed As discussed in the justification for proposed ACTION c changes ACTION e.
above, this change is acceptable.
5.
ACTION f:
With both diesel generators 11 and 12 inoperable, diesel generator 13 is presently recuired to be tested within ? hours and at least o or 12 to be returned to service within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to avoid plant shutdown and thereafter.
also demonstrate the operability of the diesel generator 13 by performing If either diesel Surveillance Requirement 4.8.1.1.2.a.4* within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
generator 11 or 17 is not returned to service within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, action must be taken to shut the plant down regardless of the operability of the diesel However, for the plant cold shutdown, the licensee may test generator 13.the only remaining onsite A.C. power source, i.e., diesel generators Therfore, testing provide assurance that this diesel generator is operable. exclu inoperable has no engineering rational and should not be imposed by the technical specifications requirement.
Based on a discussion with the licensee, the licensee a accordingly.
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6.
ACTION g:
Present ACTION f for diesel generator 13 inoperable requires testing of diese generators 11 and 12 within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 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 The proposed change deletes the requirement to test diesel generators 11 a The licensee provides a justification that diesel generator 13 supplies power to only the HPCS system and is not connected to diesel generators 11 12.
12 or the loads they supply, and also diesel generator 13 is a different type and is manufactured by a different company from diesel generators 11 and 12 hence common mode failure is not a likely occurrence.
According to 3/4.5 " Bases of Emergency Core the Cooling System," in the Gr Gulf Technical Specifications, ECCS Division 1 consists of the low pressure core spray system and low pressure coolant injection subsystem "A" of RHR system and the automatic depressurization system (ADS) as system "A"."B" and "C" of the RHR system and the automatic depressurization system as ECCS Division 3 consists of the high pressure actuated by trip system "B".The HPCS system is provided to assure that the reactor co is adequately cooled to limit fuel clad temperature in the event of a small core spray system.
break in the reactor coolant system and loss of coolant which does'not resu in rapid depressurization of the reactor vessel.
With the HPCS system inoperable, adequate core c In addition, the redundant diversified automatic depressurization system. rea taken in the safety analysis, will automatically provide makeup at reactorFor a g operating pressures on a reactor water level condition. basis core spray (HPCS) requires the function of both the LPCS and LPCI systems powered by its respective onsite A.C. electrical sou separate, the three divisional ECCSs perfonn their emergency core cooli functions as complementary to one another.
with the licensee's premise that the failure of diesel gererator 13 which supports the HPCS does not affect the ECCS functions of LPCS and L j
supported by diesel generator 11 or 12.
and our evaluation, with the HPCS diesel generator inoperable the diesel generators 11 and 12 are required to demonstrate their operability by t Therefore, the proposed change to delete the requirements to test diesel generators 11 and 12 in response to an in Surveillance Requirement.
However, with a view to reduce i
diesel generator 13 (HPCS) is denied. unnecessary testing of dies f
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r b approval of a change to current Technical Specification requirements of "within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 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 />" to "once within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />."
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7.
ACTION h and ACTION i:
Based on the discussion of the LC0 in the Technical Specification of Grand Gulf as described in item 6, ACTION g above, the new requirements in the proposed ACTION h and ACTION i are not acceptable.
SURVEILLANCE REQUIREMENTS 4.8.1.1.2.a.4 and 4.8.1.1.2.a.5 8.
A footnote is proposed to be added to each of these Surveillance Requirements to specify relaxations in the present cold start and loading requirements.
With the proposed changes all diesel generator starts for the purpose of these The surveillance requirements may be preceded by an engine prelube period.
4 footnote to Surveillance Pequirement 4.8.1.1.2.a.4 proposes that diesel generator starts (10 sec) from standby only be performed once per 184 days.
All other starts for the purpose of satisfying Surveillance Requirement 4.8.1.1.2.a.4 may be preceded by warmup procedures as recommended by the manufacturer so that the mechanical stress and wear on the diesel engine is The proposed change of the footnote regarding the diesel generator starts and gradual loading are consistent with the guidelines in GL 84-15 and minimized.
therefore is acceptable.
9.
TABLE 4.8.1.1.2-1 Testing the diesel generator provides a degree of assurance of the availability The DG testing concept reflected on this of the DGs during between tests.
table is that the above assurance has to be demonstrated with more frequent Thus, current TS requires that i
testing as the number of DG failures increases.
diesel generators be tested in accordance with RG 1.108 where the t depends on the demonstrated DG failure.
conservatively on a per nuclear unit basis, rather than on a per diesel i
Test intervals that are too short could have an adverse I
generator basis.
The staff and industry consensus is that current r
impact on DG reliability. requirements for testing of good DGs do not improve and may be a factor in potential degradation of the good DGs and may have negative effects on their overall expected life and hence such testing is not Therefore, we concur with the licensee's proposal to limit DG failure on a per diesel generator basis rather than on a per nuclear unit basis warranted.
4 This is and the frequency of testing a DG will be based on its own failure.
consistent with General letter 84-15 guideline on DG reliability and is, therefore, acceptable, 4.8.1.1.2-1, The licensee has proposed changes to Technical Specification Table i
to include routine testing at intervals of 31 days and seven days based on number of failures per diesel in the last 20 tests.
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is based on GL 84-15 reliability program which gives a diesel generator reliability goal of 0.95 and is a part of ongoing generic issue GI B-56 on i
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. Diesel Generator Reliability in Support of USI A-44 Station Blackout Therefore, the staff has concluded that the present Grand Gulf Resolution.
Technical Specification, which maintain a reliability goal of 0.99, is consistent with the Standard Technical Specifications and should not be changed Therefore, the request to until the final resolution of GI-B-56 and USI A-44.
include routine testing based on the number of failures per diesel in the last 20 tests for a reliability goal of 0.95 is not acceptable.
However, with a view to reduce unnecessary testing a DG the staff recommends approval of a change to current Technical Specifications Table 4.8.1.1.?-1 of the minimum interval of every three days to a minimum of every seven days.
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3.0 CONCLUSION
The licensee has proposed general reductions in the testing frequency requirements for the onsite emergency diesel generators in the Grand Gulf These changes involva both routine surveillance Technical Specifications.
The testing and special testing due to restriction of the plant operation.
staff has reviewed the licensee's submittals and concludes the following:
Reckoning diesel generator failures on a per diesel generator basis rather (1) on a per nuclear unit basis is consistent with GL 84-15 and is,'therefore, acceptable.
Testing of diesel generators at intervals of 31 days and 7 days based on (2) the number of failures per diesel generator in the last 20 tests and 100 tests is not in accordance with Standard Technical Specifications and is, therefore, unacceptable.
Reducing testing of diesel generators on Grand Gulf from every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to (3) once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when a diesel generator or offsite supply is inoperable is in accordance with GL 84-15 and is, therefore, acceptable.
However, an additional condition to ACTION a statement which reads "If a diesel generator of the above required A.C. electrical power sources has not been successfully tested within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to entry into this ACTION Statement," and an additional condition to ACTION b statement which reads "If the diesel generator is inoperable due to any cause other than preplanned preventative maintenance or testing...." are inconsistent with Standard Technical Specifications objectives and therefore, these j
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additional conditions are denied.
With both diesel generators 11 and 12 inoperable, the diesel generator 13 (4) is presently required to be tested for availability within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and at The proposed change in ACTION f least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter.
statement will require diesel generator 13 testing only once within 8 i
i hours.
As stated in our evaluation above, with diesel generator 11 and 12 both l
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7-l inoperable, the provisions of this action require either inoperable diesel generator 11 or 12 to be returned to service within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to avoid plant shutdown and also demonstrate the operability of the only remaining onsite Testing A.C. power source, i.e., diesel generator 13, within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
exclusively the diesel generator 13 with both diesel generators 11 and 12 inoperable has no engineering rational and should not be imposed by the technical specifications requirement. The licensee agrees with modified Action f.
Licensee's request to delete the existing Technical Specification 1
(5)
Surveillance Requirements for diesel generator 11 and 12 when diesel generator 13 (HPCS) becomes inoperable is not acceptable for reasons.given in the above evaluation. However, the staff recommends a change to current Technical Specification requirements of "within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 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 />" to "once within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />."
The footnotes propose that diesel generator starts (10 sec) and loading (6)
All other (60 sec) from standby only be performed once per 184 days.
starts for the purpose of satisfying Surveillance Requirements 4.8.1.1.2.a.4 and 4.8.1.1.2.a.5, may be preceded by warmup procedures and may also include gradual loading as recommended by the ma j
The proposed changes follow the guidance provided in GL 84-15 to reduce Also, it is the staff's engineering judgement that an cold fast starts.
overall improvement in diesel engine reliability and availability can be gained by performing diesel generator starts for surveillance testing using engine prelube and gradual loading procedures as recommended by the The proposed changes manufacturer to reduce engine stress and wear.
l incorporate these recommendations by requiring fast start criteria (10 sec) and fast load criteria (60 sec1 to be imposed only once per 184 days, and by allowing wannup before the diesel engine starts and gradual loading J
for tests other than those performed once per 184 days and therefore these proposed footnotes are acceptable.
It should be noted that some of the proposed changes to the Surveillance Requirements which are not acceptable at this time are part of the ongoing Some of the above generic issue GI B-56 on Diesel Generator Reliability.
approved changes are acceptable as an interim action on d i
letter 84-15 guidelines.
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