ML20058G278
| ML20058G278 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 11/29/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058G274 | List: |
| References | |
| NUDOCS 9312090162 | |
| Download: ML20058G278 (6) | |
Text
.
7 #" tog %
UNITED STATES j j NUCLEAR REGULATORY COMMISSION
-[ g
- WASHINGTON. D.C. 20566 0001 s, m /
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ;
RELATED TO THE INSERVICE TESTING PROGRAM RE0 VESTS FOR RELIEF BOSTON EDISON COMPANY ,
PILGRIM NUCLEAR POWER STATION ,
DOCKET NUMBER 50-293 f
i
1.0 INTRODUCTION
l The Code of Federal Regulations,10 CFR 50.55a, require that inservice testing l (IST) of certain At E Code Class 1, 2, and 3 pumps and valves be performed in !
accordance with Section XI of the ASME Boiler and Pressure Vessel Code and l applicable addenda, except where alternatives have been authorized or relief i has been requested by the licensee and granted by the Commission pursuant to 10 CFR 50.55a(a)(3)(i), (a)(3)(ii), or (f)(6)(i). In proposing alternatives '
or requesting relief, the licensee must demonstrate that: j (1) the proposed alternatives provide an acceptable level of quality and ;
safety; (2) compliance would result in hard.thip or unusual difficulty without !
a compensating increase in the level of quality and safety; or (3) conformance ;
is impractical for its facility. NRC guidance contained in Generic Letter !
(GL) 89-04, " Guidance on Developing Acceptable Inservice Testing Programs," '
provides alternatives to the Code requirements determined acceptable to the ,
staff without further NRC review. Implementation of the GL 89-04 positions is i subject to inspection. !
Section 10 CFR 50.55a authorizes the Commission to approve alternatives and to grant relief from ASME Code requirements upon making the necessary findings.
The NRC staff's findings with respect to authorizing alternatives and granting or not granting the relief requested as part of the licensee's IST program are contained in this Safety Evaluation (SE).
Furthermore, ir, rulemaking to 10 CFR 50.55a effective September 8,1992, (see 57 Federal Reoister 34666), the 1989 Edition of ASME Section XI was incorporated in 10 CFR 50.55a(b). The 1989 Edition provides that the rules.
for IST of pumps and valves shall meet the requirements set forth in ASME I Operations and Maintenance Standards Part 6 (OM-6), " Inservice Testing of Pumps in Light-Water Reactor Power Plants," and Part 10 (OM-10), " Inservice Testing of Valves in Light-Water Reactor Power Plants." Pursuant to 10 CFR 50.55a(f)(4)(iv), portions of editions or addenda may be used provided that j all related requirements of the respective editions or addenda are met, and '
subject to Commission approval. Because the alternatives meet later editions i of the Code, relief is not required for those inservice tests that are !
conducted in accordance with OM-6 and OM-10, or portions thereof, provided all l related requirements are met. Whether all related requirements are met is subject to NRC inspection.
he j
The IST program evaluated in this SE covers the third ten-year IST interval for the Pilgrim Nuclear Power Station (PNPS). The interval began December 10, 1992, and ends December 9, 2002. The third ten-year interval IST program is based on the requirements of the 1986 Edition, of the ASME Section XI Code.
The 1986 Edition references OM-1-1981 for setpoint testing of safety and relief valves. The licensee has indicated that they are using OM-1-1987 for setpoint testing of safety and relief valves. The September 1992 rulemaking, by endorsing OM-10, also incorporated OM-1-1987. The staff has determined that it is acceptable for a licensee to use OM-1-1987, and therefore, the licensee's i corporation of this edition of OH-1 is acceptable per 10 CFR 50.55a(f)(4)(iv).
2.0 EVALUATION Three relief requests were submitted in Boston Edison Company's letter of .
Novemer 10, 1993. The three relief requests are evaluated below.
2.1 Relief Reouest RV-03 Relief from the leak rate test requirements for the primary containment vacuum relief valves was granted in the NRC's SE for the third ten-year interval relief requests issued June 23, 1993, and remains unaffected by the revision of the relief request. RV-03 has been revised to include relief from the set pressure test frequency of OM-1-1987, Paragraph 1.3.4.3, " Primary Containment Vacuum Relief Valves." These valves are normally closed and open to equalize the pressure between the volume of the pressure suppression chamber and the drywell when the suppression chamber pressure exceeds the drywell pressure.
2.1.1 Licensee's Basis for Relief Relative to the revision for set pressure frequency, the licensee states:
ANSI /ASME [American National Standards Institute /American Society of Mechanical Engineers] OM-1 [ Operations and #aintenance Standards, Part 1, " Requirements for Inservice Performance Testing of Nuclear Power Plant Pressure Relief Devices") requires operability testing of primary containment vacuum relief valves at a six month frequency. This testing standard states, "The valves shall be actuated to verify open and close capability, set pressure and performance of any pressure and position sensing accessories." These vacuum relief valves have restricted access which prevents normal set pressure verification during power operation.
These valves are located within a hazardous environment (N 2 inerted),
and require removal of a bolted primary containment (torus) manway hatch and installation of temporary lighting for set pressure verification.
These valves are exercised quarterly. They also receive Technical Specification required manual manipulation with position switch calibration and functional testing, which is performed locally every Refuel Interval. Set pressure verification is accomplished using a test gauge (i.e, push-type) on the valve disk in conjunction with the Technical Specification required testing.
i 1
t 2.1.2 Alternative Testina The licensee proposes:
Valve set pressure operability test shall be performed in conjunction with the Technical Specification testing once every Refuel ' Interval, i
2.1.3 Evaluation The periodic set pressure verification required by OM-1-1987 ensures that the primary containment vacuum relief valves will open at the differential pressure analyzed for the plant in the safety analysis for the applicable .
accident scenarios. The subject valves at the PNPS are located in an inaccessible area. Performance of the set pressure test requires access to t the valves to physically apply pressure directly on the valve disk with the ;
test gauge. It is impractical to perform the testing during power operations.
- While access to the area may be allowed during cold shutdown conditions, containment integrity would not be maintained once the torus manway hatch is ,
opened. Additionally, the environment in the area where the valves are ;
located would be hazardous during most cold shutdown outages, requiring !
special personnel protection, and the extent of the test setup could extend an !
outage solely to complete IST. Therefore, set pressure testing is impractical to perform during cold shutdown conditions. To impose the 6-month test !
interval would be a burden to the licensee in that (1) an extended plant !
shutdown could be required to prevent subjecting personnel to a hazardous ;
environment, (2) personnel would be subjected to a hazardous environment to +
perform testing during power operations or cold shutdown outages, or (3) the l licensee would have to design and install an in-place test device with remote i indication with hardware that may not be available and which may not currently {
be feasible. -
The impracticality of performing set pressure testing of the inaccessible !
primary containment vacuum relief valves at a 6-month interval prompted changes in Appendix I, " Inservice Testing of Pressure Relief Devices in Light-Water Reactor Power Plants," of the Operations and #aintenance Code which has )
replaced OM-1-1987. The test interval will be specified as "aach refueling l outage or every 2 years, whichever is sooner, unless historical data requires l more frequent testing." The PNPS Technical Specifications (TSs) require set C pressure verification each refueling interval. Provided this interval is !
consistent with "each refueling outage or every 2 years, whichever is sooner,"
the proposed frequency will be in accord with the revision to the Code testing {
requirements. Industry data do not indicate problems with these valves, other j than problems associated with the stroking apparatus which performs no i function other than to allow periodic stroking of the disk-(no function i related to valve opening to relieve vacuum, and thus no impact on the set pressure). Unless plant-specific data indicate that more frequent testing is necessary, the extended interval will adequately ensure the operational readiness of these valves.
Therefore, the extension of the test interval to the interval specified in the TSs and the revised Code (i.e., once each refueling outage, unless a refueling
interval exceeds 2 years due to an extended cold shutdown, in which case -
testing should be performed during the extended cold shutdown as well as during the refueling outage) is acceptable.
2.1.4 Conclusion Relief from the test frequency requirements of Paragraph 1.3.4.3 of OM-1-1987 is granted: (1) based on the impracticality of performing the primary ,
containment vacuum relief valves set pressure testing once each 6 months, (2) in consideration of the burden on the licensee if the requirements were imposed, and (3) in consideration of the adequacy of the alternative tening.
for ensuring the operational readiness of the valves, pursuant to 10 CFR :'
50.55a(f)(6)(1).
2.2 Relief Reouest RV-42 Relief concerns the test frequency requirements of IW-3521 for check valve 301-CK-151 in the control rod drive (CRD) system. This valve allows the flow of high pressure water to the CRD mechanisms for cooling and positioning control rods (during both normal and scram conditions). The valve also closes to isolate a potential leakage pathway for primary coolant to leak past both t the primary and secondary containment boundaries via the CRD hydraulic system following a design bases accident loss-of-coolant accident.
2.2.1 Licensee's Basis for Relief The licensee states: l This is the Control Rod Drive Hydraulic (CRDH) Supply Header Check Valve for a system required to be in service during plant operation. This normally open check valve was newly installed during RF0 [ refueling outage] 9 (May 1993) and requires a reverse flow exercise, The open i normal position verification is performed on a quarterly basis. ;
The most practical method for performing a reverse flow exercise is to i conduct a seat leakage-test. All reverse flow exercise test methods require CRDH flow to the CRD mechanisms and reactor coolant !
recirculation pump seals to be secured. Isolating _ the CRDH flow during t power operation interrupts the flow for maintaining and controlling i control rod positions. Pressure would decay from the isolated system, !
causing control rods to drift from their positions,-requiring immediate ,
plant shutdown. '
Interrupting CRD flow during cold shutdowns to allow valve closure terminates seal purging functions to the CRD mechanisms [CRDMs] and - -i reactor coolant recirculation pump seals, which can negatively affect seal performance. Particularly for the CRD mechanisms [CRDMs], flow interruptions of seal purging tend to impact smooth performance on some CRDMs (causing sticking) which could delay plant startup and is not i recommended industry practice except during extended maintenance / refuel outages.
i Therefore, verifying a reverse flow exercise more frequently than that used for seat leakage testing would create a hardship without a
- compensating increase in the level of safety due to increased equipment
, performance problems, which are created by removing and returning the i system from service to allow valve closure for testing.
2.2.2 Alternative Testina The licensee proposes: :
. Exercise valve closed at least once every two years, during seat leakage )
testing, i 2.2.3 Evaluation )
l The Code requirements of IWV-3521 to exercise check valves once each quarter, 1 or during cold shutdowns as allowed by IWV-3522 when exercising during plant operation is impractical, were established to detect degradation prior to a valve reaching a condition of inoperability and thereby ensure that the tested valves would perform as required when needed. The subject valve is open during power operations and must remain in the open position to maintain cooling water to the control rods. Closing the valve during power operations would also step cooling water to the reactor coolant recirculation pump seals
- which could result in damage to the seals which are susceptible to temperature transients from interruption of cooling flow.
It is impractical and burdensome to perform closure testing of the valve during cold shutdown outages for several reasons identified in the licuase's basis for relief. Cooling water for the CRDMs and the reactor coolant recirculation pump seals remain in service during most cold shutdown conditions. Interruption of CRD flow negatively impacts the CRDMs and the pump seals, with seal purging interruptions of the CRDMs causing sticking and with cooling flow to the pump seals possibly causing seal damage. Either !
condition could cause equipment damage, or possibly failure, and delay startup- i to effect repairs.
]
In recognition that there are valves for which testing is impractical to perform during both power operations and cold shutdowns, OM-10, " Inservice !
Testing of Valves in Light-Water Reactor Power Plants," Paragraph 4.3.2.2(e), ;
specifies for check valves that "if exercising is not practicable during plant i operation or cold shutdowns, it may be limited _ to full-stroke during refueling outages." While the opening function of the valve is verified quarterly in the course of normal operations, as discussed above, it is impractical to perform verification of the capability of the valve to close quarterly or during cold shutdown outages. Therefore, it is acceptable for the licensee to follow the requirements of OM-10 and extend the verification of closing of the valve to refueling outages. The capability of the valve to close will be verified by the performance of a seat leakage test each refueling outage. The related < !quirements of OM-10 are included in Paragraphs 4.3.2.1, 4.3.2.2, 4.3.2.3 ppening capability during normal operations), 4.3.2.4, 4.3.2.5, and 4.3.2.6.
I l L
l i
2.2.4 Conclusion l
Approval of the alternative test frequency is authorized in accord with 10 CFR !
50.55a(f)(4)(iv) which specifies that IST may meet the requirements of later l editions of the Code incorporated in 10 CFR 50.55a(b), subject to Commission j approval, or portions of the Code, provided all related requirements' are met. l The related requirements are listed above. Implementation-is subject to NRC j inspection. j 2.3 Relief Reauest RV-43 1 i
f I RV-43 concerns the nuclear boiler vessel instrumentation check valves that :
open to allow CRD water to each of two emergency core cooling system water. )
level reference legs. The valves prevent reverse flow from the instruments >
racks back into the CRD system. The valves are classified and non-Code. NRC approval of relief requests associated with non-Code components is not' i required per 10 CFR 50.55a. However, it is acceptable for the licensee to '
include non-Code components in the IST as discussed in Position 11 of i
)
GL 89-04, " Guidance on Developing Acceptable Inservice Testing Programs." l Therefore, the relief request is not further evaluated. j i
3.0 CONCLUSION
I 9
The staff concludes that the relief requests as evaluated and modified by this i d
SE will provide reasonable assurance of the operational readiness of the pumps and valves to perform their safety-related. functions. The staff has determined that granting relief pursuant to 10 CFR 50.55a(f)(6)(1) and i 1 approving alternatives pursuant to 10 CFR 50.55a(f)(4)(iv). is authorized by ;
1 law and will not endanger life or property, or the common defense and security 1 and is otherwise in the public interest. In making this determination, the- i staff has considered the impracticality of performing the required' testing and the burden on the licensee if the requirements were imposed..
Principal Contributor: Patricia Campbell, DE/EMEB
- Dated: November 29, 1993 1
l
.U p-r,.- --
e e ,e - , , , , . ,..m-.., ..w.,-,- ,..,,,,.,4c.w-. - .w.g-,.w--en. ,. -,wa, -+---,w..,,,- ,,,.,g- n