ML20137Z701
| ML20137Z701 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 03/03/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20137Z391 | List: |
| References | |
| NUDOCS 8603130096 | |
| Download: ML20137Z701 (7) | |
Text
_
_.y_
i J
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORT EXEMPTION FROM APPENDIX J FACILITY OPERATING LICENSE NO. NPF-39 PHILADELPHIA ELECTRIC COMPANY jl MONTG0MERY COUNTY, PENNSYLVANIA
)'
LIMERICK GENERATING STATION, UNIT NO. 1 DOCKET NO. 50-352 t
i 1.0 Introduction l
i l
By letter dated December 18, 1985, the Philadelphia Electric Company (the t
i licensee) requested a one-time-only approval to temporarily extend certain surveillance requirements in the Technical Specifications, which must be performed nominally every 24 months and which can only be done when the plant l
is shutdown. The change would extend the 24 month surveillance intervals for j
leakage testing of selected containment isolation valves by up to 12 weeks i
beyond the time allowed by the Technical Specifications. This would perr.it the licensee to delay performing this testing until a maintenance and s
i surveillance outage which will begin on or before May 26, 1986. The staff has found that approval of the proposed change to the Technical Specification
{
j would also require the granting of an exemption from Appendix J along with the issuance of the requested amendment.
l
)
By letters dated January 29, February 5, February 25 and March 3, 1986 the licensee provided additional information in support of the proposed changes.
Technical Specification (TS) 4.6.1.2.d requires that Type C tests shall be l
conducted at intervals no greater than 24 months except for tests involving l
valves in hydrostatically tested lines. The 24 month interval for this Type C i
testing is consistent with the requirements of 10 CFR Part 50, Appendix J.
paragraph III.D.3 which specifies that Type C tests shall be performed at l
i l
intervals no greater than 2 years. The licensee's letter of December 18, 1985 requested an extension of the 24 month TS testing requirement by a maximum of 4
12 weeks for a group of 27 isolation valves.
In addition, in the December 18, l
l 1985 letter the licensee requested a one-time exemption from the Appendix J 24 month testing requirements for these 27 valves.
J Paragraphs III.C.3 and !!!.0.3 of Appendix J require that containment isolation valves which may provide a pathway for leakage of containment atmosphere are 4
required, on at least a 24 month frequency, to have their leakage measured for comparison with the limiting value of 0.6 L for Type B and Type C tests.
I Paragraph!!I.C.3alsoprovidesthatleakag$fromisolationvalvesthatare sealed with fluid may be excluded from the summation of Type B and Type C tests.
l Consistent with this provision the licensee has identified that 10 of the i
37 valves addressed in the December 18, 1985 application amendment are sealed I
by fluid and therefore are hydrostatically tested on a nominal frecuency of t
]
18 months. The acceptability of hydrostatically testing these valves in the r
A i
j fEI %a j
4 2-1 shutdown cooling return line and in the low pressure coolant injection line is addressed in Section 6.2 of the Limerick Safety Evaluation Report dated August 1983. The measured leakage from these hydrostatically tested valves is compared to the limit of I gallon per minute in the pressure isolation valve section of the TS and not to the 0.6 L criteria for Type B and Type C tests and accord-ingly the testing of these 0alves is not within the scope of the issues addressed by the licensee's exemption request. The acceptability of the sur-veillance extension for hydrostatically tested valves is addressed in the safety evaluation accompanying the amendment to the technical specifications.
2.0 Evaluation Since the Limerick Unit 1 plant has been through an extended startup program schedule, which included relatively little startup testing program activity frem about April to early August 1985, the scheduled surveillance tests fall in a period of what would otherwise be a continuation of first fuel cycle power operations.
Since the plant must be shutdown for about two weeks to perform these tests and since the licensee plans to shut the plant down on or before May 26, 1986 to perform other surveillance tests and maintenance activities the licensee proposes to extend the surveillance interval for these isolation valves to allow those tests to also be performed during the outage to begin on or before May 26, 1986. The end of the present most limiting surveillance interval is March 3, 1986.
The requirements of the TS for which extensions are proposed and the reason these tests can only be performed while the reactor is shutdown are as follows.
General Design Criterion 56, Primary Containment Isolation, requires that lines to be isolated be provided with an isolation valve inside containment and an isolation valve outside containment. The design of the isolation valves and their associated piping and test connections requires personnel access to the primary containment to isolate the valve inside the containment from the balance of its associated system and to implement the test procedure. Entry into con-tainment during power operations would expose personnel to the hazards of high air temperature (about 120'F), radiation exposure that is high with respect to as-low-as-reasonably-achievable (ALARA) standards (about 10 R/ hour in represen-tative areas) and the nitrogen environment of the inerted containment atmosphere for which self contained breathing apparatus (SCUBA) would be reovired. The licensee has stated orally that they consider the hazard of the inerted contain-ment atmosphere to be too great to permit personnel access for routine plant operational tasks. The licensee has also stated that further factors which preclude testing these valves at power include the need to depressurize the reactor, drain the reactor enclosure chilled water (RECW) system, drain the dry-well chilled water (DCW) system, drain the emergency service water (ESW) loop, remove the reactor recirculation pumps from service or a combination of the above.
The staff concludes that the licensee has shown that it is not practical or feasible to test these valves at power and that the plant would be required to
. shutdown for about two weeks to cooldown, depressurize and conduct the tests beginning on March 3, 1986 unless the requested extension in surveillance test periods is granted.
The licensee has stated that the types of valves subject to this surveillance schedule extension request have traditionally good maintenance histories and do not include those valves known to be maintenance intensive in boiling water reactors such as the main steam isolation valves or the feedwater check valves.
The licensee also points out that these valves are used in applications where they are either normally open or normally closed and are not used in a modulatino mode to control flow rates. The licensee further states that such valves when used in non-aodulating applications tend not to have problems meeting leakage criteria.
In this regard, the licensee has also considered the leak rate in-formation reported in Licensee Event Report (LER) No. 352/85-102. This LER deals with a valve that is not within the scope of the Limerick surveillance schedule extension request. The licensee has reached a determination, with which the staff concurs, that the LER 85-102 event was an isolated event and as such has no significant effect upon the conclusions and basis for the request for extension.
In support of the position that these valves are reliable in meeting leakage criteria the licensee has interrogated the Nuclear Plant Reliability Data System (NPRDS) for similar types of valves and has reviewed these specific valves' previous leakrate test histories.
The NPRDS query serves as a useful qualitative estimation of these valves' reliability since the reporting of data to the system is on a voluntary basis and therefore there is no representation that the data from the system repre-sents all of the valves in the industry of that specific valve type. Never-theless, the data as presented in the licensee's letter dated January 29, 1986, is useful in considering whether these valve types are generally reliable in meeting their leakage criteria.
The licensee notes that the valves in the NPRDS data base have been in service for significant periods whereas the Limerick valves will have experienced only a part of the first fuel cycle's operating time by the date of the next planned surveillance test. The NPRDS data does not suggest that these valves, either individually or collectively, should be expected to experience undue difficulties in meeting the leakage criteria.
The licensee states that testing has been performed on those valves that can be tested at power such that only 27 valves out of a total of 245 valves in Part A of TS Table 3.6.3-1 require the one-time extension of the 24 month surveillance interval. This is reflected in the following specific system discussions wherein, as applicable, it is noted that the extension request does not apply to all of the valves in a given system since the other valves have been tested on a more recent schedule which does not require their retest until af ter May 26, 1986.
. Technical Specification 4.6.1.2.d-Twenty-Four Month Tests There are 27 valves subject to this specification for which the licensee has requested one time extension of no more than 12 weeks in the surveillance test schedule. These valves are as listed below.
System Valve Number Size / Type
- LPCI injection loops HV-51-1F017A.C,0 12" gate i
A.C.D
- Suppression Pool Spray HV-51-1F027A 6" globe
- Reactor enclosure cooling water
- supply line HV-13-106,108,109 3" and 4" gate
- return line HV-13-107,110,111 3" and 4" gate
- Drywell Cnilled Water, Loops A and R
- Supply lines HV-87-120A, 125A, 128 8" gate and 1208, 1258, 122
- Return lines HV-87-121A, 124A, 129 8" gate and 1218, 1248, 123
' Reactor Water Cleanup HV-44-lF001, 1F004 6" globe supply line
- Recirculation Cump B seal 43-1004B 1" check purge
- Instrument Gas Supply to HV-59-151B 1" globe ADS valves E and K 59-1112 1" check The licensee's letter of January 29, 1986 also provides information on the previous leakage testing for the specific valves which are subject to this amendment request. As indicated in the licensee's letters, the total leakage measured as a result of the previous tests on all applicable Type C valve tests is about 22,000. standard cubic centimeters per minute (SCCM) which is about 23% of the total allowed by the Technical Specifications. Of this 22,000. SCCM only about 3800. SCCM (or 4% of the TS limit) was contributed by the 27 valves subject to the amendment application.
Thus, it may be seen that leakage through these valves would have to increase many tires before they contributed a lar portion of either (1) the total measured leakage from all such valves or (2)gethe TS limit value.
Some discussion of the individual valves is provided below, i
I J
1 l
[
1 1e LPCI Injection l
Valves HV51-1F017A, C and D require an extension of less than 10 weeks in a 24 month surveillance interval. The comparable valve in the B loop was tested l
on a schedule which does not require its retest until after May 26, 1986. The l
leakage from these three valves during the previous tests totaled 1210 SCCM or l
1% of the TS limit valve.
The line in which these valves are located is pro-vided with instrumentation which will detect and annunciate excessive leakage past the valves.
Suppression Pool Spray l
Valve HV-51-1F027A requires an extension of about 8 weeks in a 24 month sur-veillance interval. The comparable valve in the B loop of suppression pool spray was tested on a schedule which does not require its retest until after May 26, 1986. The leakage from this valve during the previous test was 2.25 SCCM or 0.002% of the TS limit valve.
Reactor Enclosure Cooling Water (RECW)
Valves HV-13-106, 108, 109 in the RECW supply line and HV-13-107, 110, 111 in the RECW return line require ar extension of 12 weeks in a 24 month surveillance interval. The leakage from these valves during the previous tests was 145 SCCM or 0.15% of the TS limit for the supply valves and 9 SCCM or 0.017 nf the TS limit for the return valves, t
i Drywell Chilled Water The valves in loops A and B of the drywell chilled water system, each loop having 3 involved valves in the supply line and 3 involved valves in the return I
line, require an extension of up to 12 weeks in a 24 month survelliance inter-val. The leakage from these valves during the initial tests was 203 SCCM for loop A supply valves, 653 SCCM for loop A return valves, 668 SCCM for loop P supply valves and 338 SCCM for loop B return valves for a total of 1862 SCCM or 2% of the TS limit.
Valves HV-44-1F001, 1F004 it, the RWCU supply line require an extension of less l
than 10 weeks in a 24 month surveillance interval. The leakage from these i
valves from previous tests was 510 SCCM or 0.5% of the TS limit value.
Recirculation Pump B Seal purge l
l Valve 43-1004B in the reactor recirculation purrp seal purge line requires an extension of 3 weeks in a 24 month surveillance interval.
The comparable j
valve in the A loop line was tested on a schedule which does not require its l
retest until after May 26, 1986. The leakage from this valve from previous l
tests was 76 SCCM or 0.1% of the TS limit value, t
4 Instrument Gas Supply to ADS Valves Valves HV-59-1518 and 59-1112 in the instrument gas supply to automatic depressurization system (ADS) valves E and K require an extension of less than 2 weeks in a 24 month surveillance interval. Comparable valves in the gas supply line for ADS valves H. M and 5 and other instrument gas supply and i
return lines were tested on a schedule which doas not require retest until after May 26, 1986. The leakage from these valic during the previous tests l
was 9 SCCM or 0.01% of the TS limit value.
Summary for 24 Month Surveillance Interval Valves i
l In assessing whether an extension of 12 weeks in a 24 month surveillance interval r
would be appropriate for these valves the staff has considered the previous leak rate test results for these valves, their propensity for requiring extensive maintenance to maintain their leak tight integrity and the consequences of any additional degradation during the requested extension. Based on its review the staff finds that:
(1) The previously measured Type C test leakage through these valves (3800 SCCM) constituted but Ih of the total measured Type C leakage.
There is con-siderable margin between these values and the limit established by Appendix J and the technical specification of 0.6 L,co(94, 964 SCCM) for the Type B and C tests. These valves were not found to ntribute either individually or collectively a disproportionate percentage of the total measured leakage or of the technical specification limit values.
(2) To date these valves have not required maintenance, repairs or adjust-ments which would reouire reperformance of their Type C test.
The licensee's review of similar valves via NPRDS provides a qualitative assessrrent that supports the licensee's findings that these valves typically have good maintenance histories, do not require intensive maintenance to ensure their leak tight integrity and thus are unlinely to degrade significantly in the period of the extensinn, t
(3) There is ample margin between the leakage previously measured during the Type C isolation valve tests, including the previout tests of the 27 valves subject to this amendment request, and the limiting leakage values in the technical specifications and in Appendix J to accommodate any degradation likely to be experienced by these 27 valves during the extension period.
Therefore the consequences of leakage past these isolation valves is bounded by safety analyses previously performed which were based on the limiting leakage values in the technical specifications and in Appendix J.
., The licensee has determined that the proposed changes to the TS will have little or no effect on containment integrity and that the proposed amendment will not alter any of the accident analyses. The staff has reviewed these determinations and the associated changes and concludes that, on the bases discussed above, they are acceptable.
In addition the staff concludes that the licensee has pro-vided sufficient bases for the tenporary extension of the 24 month surveillance interval required by Appendix J and that a temporary exemption from the require-ments of Paragraph III.D.3 is acceptable.
3.0 Conclusion The staff has concluded, based on the considerations discussed above, that the proposed temporary exemption frnn 10 CFP 50, Appendix J. Paragraph !!!.D.3 is authorized by law, will not endanger life or property or the corr,on defense and is otherwise in the public interest and should be granted.
Cated: Marc 5 3,1986