ML20046C346
| ML20046C346 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 07/16/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20046C329 | List: |
| References | |
| GL-89-04, GL-89-4, NUDOCS 9308100165 | |
| Download: ML20046C346 (8) | |
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UNITED STATES l'
NUCLEAR REGULATORY COMMISSION (v
8 WASHINGTON, D.C. 20555-0001 j
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RELIEF RE0 VESTS IOWA ELECTRIC LIGHT AND POWER COMPANY DUANE ARNOLD ENERGY CENTER DOCKET NUMBER 50-331 t
1.0 INTRODUCTION
The Code of Federal Regulations, 10 CFR 50.55a(f), requires that inservice testing (IST) of certain ASME 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 applicable addenda, except where relief has been requested by the licensee and granted by the Commission pursuant to s50.55a(f)(6)(i), or where the alternative has been authorized pursuant to 550.55a(a)(3)(i) or (a)(3)(ii).
In requesting approval of alternatives to or relief from the Code requirements, the licensee must demonstrate that:
(1) the proposed alternatives provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance with certain requirements of the applicable Code Edition and addenda is impractical for its facility. Section 50.55a(f)(4)(iv) provides that inservice tests of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in s50.55a(b) subject to the limitations and modifications listed, and subject to Commission approval. NRC guidance contained in Generic Letter (GL) 89-04, Guidance on Developing Acceptable Inservice Testing Programs, provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives in Positions 1, 2, 6, 7, 9, and 10, provided the licensee follow r
the guidance delineated in the applicable position. When an alternative is proposed which is in accordance with GL 89-04 guidance, and is documented in the IST program, no further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
Furthermore, in rulemaking to 10 CFR 50.55a effective September 8,1992, (See 57 Federal Reaister 34666), the 1989 edition of ASME Section XI was incorporated in s50.55a(b).
The 1989 edition provides that the rules for IST of pumps and valves shall meet the requirements set forth in ASME 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 (f)(4)(iv), portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met, subject to Commission approval, and J
therefore, relief is not required for those inservice tests that are conducted i
in accordance with OM-6 and OM-10, or portions thereof. Whether all related requirements are met is subject to NRC inspection.
9308100165 930716 DR ADOCK 05000331 l
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i These regulations authorize the Commission to grant relief from, or approve alternatives for ASME Code requirements upon making the necessary findings.
The NRC staff's findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST Program are contained in this Safety Evaluation (SE).
The enclosed SE provides the evaluations of relief requests for the Duane Arnold IST program submitted by the licensee in their letter dated January 29, 1993.
In response to a request of the staff, the licensee submitted additional information in a letter dated March 1,1993, which included the 10 CFR 50.59 evaluation of the modification discussed in Section 2.2 below.
Evaluations of the three relief requests are provided below.
2.0 REVISED RELIEF RE0 VESTS The revised relief requests in the January 29, 1993, submittal included VR-003, VR-004, and VR-005.
2.1 Relief Reouest VR-003 L
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The licensee has requested relief from the Code test frequency requirements of ASME Section XI, Paragraph IWV-3521, for the check valves V-19-0149 and V-20-0082, which are located in the interface between the low pressure safety injection (LPSI) and recirculation systems.
The licensee has proposed to partial-stroke one of the two valves each cold shutdown and full-stroke both valves each refueling outage.
In the staff's SE dated March 11, 1992, the original relief request was preapproved in accordance with GL 89-04, and therefore not further evaluated.
I The licensee has resubmitted the relief request due to a revision in the method of testing these check valves.
The Code requires that these valves be exercised once every three months to the position required to fulfill their safety function.
These valves have a safety function in the open position to allow injection of LPSI flow into the recirculation system and a safety function to close to prevent a diversion of flow from the recirculation system. The licensee is requesting that the valves be exercised to meet IST requirements each refueling outage.
Valve j
stroking will be accomplished by attaching a mechanical indicator to the rotating shaft of the check valve before each test to indicate check valve position when the valves are stroked to
.e full open position using system
)
fl ow.
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2.1.1 Licensee's Basis for Recuestino Relief The licensee states:
"These valves cannot be stroked during power operation because the RHR [ residual heat removal] pumps cannot develop sufficient head to overcome recirculation system pressure.
These valves cannot be manually stroked during operation because they are located in the drywell and are inaccessible.
4.
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. In-situ testing has determined that these check valves fully open at approximately 4000 gpm. To ensure compliance with IWV-3522, positive verification of valve operation is required. To achieve this verification, a mechanical indicator is attached to the rotating shaft. This testing cannot be conducted at cold shutdown because the containment is inerted with nitrogen.
In order to gain personnel access to the drywell, the nitrogen must l
be vented (normally a 16 - 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> operation). The containment must be re-inerted before the plant is restarted (another 16 - 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> operation).
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Inerting and de-inerting the drywell solely for the purpose of valve testing is excessively burdensome. Additionally, a full stroke test of these valves cannot be performed with flow at cold shutdown because it would be necessary to test two channels / loops of a safety system at the same time.
Current
'l guidance only allows the operation of one train of a safety system for l
surveillance purposes.
3 One of these valves is partially stroked during cold shutdown for the operation of the shutdown cooling mode of RHR. This is only a partial stroke test as the normal flow rate in this mode is only 4000 gpm vs a maximum i
required accident flow rate of 14,400 gpm and no positive verification of j
valve position is made. While shifting system operation to the idle loop is possible, it is a time consuming operation.
In order to change loops and inject cooling flow through the other loop, more than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of preparation and lineup work would he required of the control room personnel, assuming no j
other testing / duties orgoing at the time "
2.1.2 Alternate Testino The licensee proposes:
"One of these valves will' be partially stroked to the l
open position each cold shutdown. V-19-0149 and V-20-0082 will be stroked to the full open position during each refueling outage, utilizing a mechanical j
position indicator to prove positive valve operation."
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2.1.3 Evaluation Testing at power operations is impractical because the RHR pumps cannot l
overcome the recirculation system pressure, which would be necessary to stroke the valves. Full-stroke testing of the check valves is impractical during cold shutdowns because the valves are located in the drywell and access is j
prohibited while the containment is inerted. Boiling water reactors with a Mark I containment, such as Duane Arnold, are required to have provisions for an inerted atmosphere during power operation. The containment is_inerted in order to protect against a hydrogen burn or explosion which may be caused by the hydrogen gas generated by the core metal-water reaction following a loss of coolant accident. Since hydrogen generation is not a concern during. cold shutdown, the TS allow the containment atmosphere to be de-inerted.- However, de-inerting is not routinely performed at cold shutdown due to the time to de-inert and re-inert, and due-to'the resulting loss of nitrogen used for inerting.. Therefore, licensees are not required to de-inert solely to perform inservice testing.
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One of the two check valves is partial-stroked each cold shutdown as a result of operation of the RHR system in the shutdown cooling mode. Operating the other loop in the shutdown cooling mode in order to partial-stroke exercise the other valve is impractical because only one loop is required and it would take several hours to switch operation to the other RHR loop which could result in a delay of startup from the cold shutdown condition. Additionally, because the RHR system is used for decay heat removal during cold shutdown conditions, one of the two valves will be exercised each cold shutdown, even if exercised within the previous 92 days.
The proposed testing is consistent with the exercising requirements specified in OM-10, Paragraph 4.3.2.2 for extension of the testing from quarterly and cold shutdown to refueling outage conditions.
Because the test frequency meets the requirements of the later edition of the Code incorporated in 10 CFR 50.55a(b), relief is no longer required to conduct this testing at the frequency allowed by 0M-10, provided the licensee implement all the requirements of Paragraph 4.3.2.2. for testing these valves and continue to document the basis for the extension in the IST program per Paragraph 6.2 of OM-10.
The proposed alternative meets these requirements.
2.1.4 Conclusion Relief is no longer required for use of this portion of OM-10, and the proposed alternative is approved pursuant to 550.55a(f)(4)(iv), provided the licensee implement all the requirements of Paragraph 4.3.2.2 and continue to i
document the basis for the extension per Paragraph 6.2.
Implementation of these related requirements is subject to NRC inspection.
2.2 Relief Reouest VR-004 Relief from the Code test frequency requirements of ASME Section XI, Paragraph IWV-3521, is requested for the reactor feedwater supply inboard isolation valves V-14-0001/0003 which perform a safety function to close to isolate feedwater flow for containment isolation (close) and perform a safety function to open to allow injection flow to the reactor through the feedwater nozzles (reference UFSAR Figure 5.1-1, Sheet 1). The valves have a normal operating function to open to provide feedwater flow to the reactor vessel. The licensee has proposed to verify closure of both valves each refueling outage by conducting an Appendix J local leak rate test (LLRT) and disassemble and inspect one of the two valves each refueling outage on a rotating schedule.
2.2.1 Licensee's Basis for Reouestino Relief The licensee states:
"The valves cannot be exercised during power operation.
i During plant operation at power, reactor feedwater is supplied through both valves to maintain reactor coolant inventory in the reactor vessel and maintain reactor vessel water level.
Closing either of these valves will isolate two of the four supplies of feedwater into the reactor vessel. This action could result in thermal shock to the reactor vessel feedwater nozzles and spargers upon resumption of flow and a plant trip due to the potential severe reactor vessel water level transients.
These valves cannot normally be tested during cold shutdown because the containment is inerted with nitrogen.
Personnel would be required to access the drywell to perform a mechanical exercise of these valves. The nitrogen must be vented (normally a 16 - 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> operation). The containment must be re-inerted before the plant is restarted (another 16 - 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> operation).
Inerting and de-inerting the drywell solely for the purpose of testing is excessively burdensome.
In addition, the LLRT is done with air, therefore, the line between the check valves and upstream isolation valve must be drained. This is a time consuming process resulting in lenathened shutdown times and unnecessary hours of exposure."
2.2.2 Alternate Testina The licensee proposes:
"The valves will be assumed to be in the open position if the feedwater system operates properly during normal plant operation. The valves will be exercised to the fully closed position each refueling outage and verified by local leak rate testing.
In addition, during each refueling outage, one of these valves will be disassembled and inspected for full stroke operability in accordance with requirements of USNRC Generic Letter 89-04.
Thus, both valves will be disassembled and inspected once eve ~ry two refueling outages.
The normal operation of the feedwater system and plant will fulfill the partial flow test of these valves."
2.2.3 Evaluation IWV-3521 and IWV-3522 of ASME Code Section XI requires that these valves be exercised to their safety position every three months. These valves function closed for containment isolation and open to allow injection flow to the reactor vessel from high pressure coolant injection and reactor core injection cooling systems (reference UFSAR Figure 5.1-1, Sheet 1) which inject into the feedwater lines upstream of these valves.
Rather than exercising the valves in accordance with the IWV-3521/3522 requirements, the licensee is proposing to exercise these valves to the closed position every refueling outage and verify closure by using a LLRT.
In addition, the licensee proposes to disassemble and inspect one valve each refueling outage and perform a full-stroke manually. Normal operation with feedwater flow ensures partial-stroke open capability of these valves. The full-stroke capability is to be verified during a disassembly and inspection sampling program per GL 89-04, Attachment 1, Position 2.
It is impractical to exercise these valves closed during full power operation.
Interruption of feedwater to the reactor vessel would cause a reactor level transient that would trip the plant unless a power reduction was initiated to perform testing.
Even with a power reduction, the transient resulting from the valve closure exercise could trip the plant or cause equipment damage and cause a thermal cycle on the feedwater nozzles and reactor internals.
These valves cannot be exercised during cold shutdowns because access to the valves would require de-inerting containment which would be an unnecessary' i
burden on the licensee.
Boiling water reactors with a Mark I containment, i
such as Duane Arnold, are required to have provisions for an inerted
. atmosphere during power operation. The containment is inerted in order to protect against a hydrogen burn or explosion which may be caused by the hydrogen gas generated by the core metal-water reaction following a loss of coolant accident.
Since hydrogen generation is not a concern during cold shutdown, the TS allow the containment atmosphere to be de-inerted.
- However, de-inerting is not routinely performed at cold shutdown due to the time to de-inert and re-inert, and due to the resulting loss of nitrogen used for inerting.
Original valves in this application experienced excessive leakage during Appendix J local leak rate tests (LLRT).
In an effort to meet Appendix J leakage limits, the original valves were replaced with Anchor-Darling spring-assisted air-operated tilting disk check valves which included an indicator / damper mechanism capable of providing disk position indication. The licensee continued to experience leakage problems subsequent to the replacement.
Leakage was attributed, in part, to the actuator over-rotating the valve disk and creating a leak path at the upper portion of the valve seating area.
The licensee eventually removed the actuator and indicator / damper mechanisms from the check valves to resolve _ leakage problems.
This modification also eliminated remote position indication.
Without remote position indication, the only method to verify closure of these valves is by performing a leak test. Due to the time required for test equipment setup and performance of a leakage test, it is impractical for the licensee to test these valves closed during cold shutdowns because a delay in startup could result.
Accordingly, while not in accordance with IWV-3521/3522, the licensee's proposed schedule for inservice testing of these valves does meet the requirements of OM-10, Paragraph 4.3.2.
Because the testing will meet the requirements of a later edition of the ASME Code, specifically the 1989 Edition, which has been incorporated in 10 CFR 50.55a(b), relief is not required.
Pursuant to 10 CFR 50.55a(f)(4)(iv), the NRC may approve the use of later editions, or portions of editions, for inservice testing.
The licensee proposes to verify closure by performing a LLRT of these valves every refueling outage. The LLRT would verify that the valves are capable of closing.
In addition, the licensee proposes to disassemble and inspect one of the two valves every refueling outage to verify the full-stroke capability.
2.2.4 Conclusion The proposed test frequency is in accordance with the most recent edition incorporated in 10 CFR 50.55a(b). Therefore, relief from the Code requirements is not required to extend the test interval from quarterly and/or cold shutdown to refueling outages per 0M-10, Paragraph 4.3.2.2.
In addition, the basis for extension of the test interval must continue to be documented in the IST program per 0M-10, Paragraph 6.2.
Provided the licensee implements the test interval extension in accordance with OM-10, Paragraphs 4.3.2.2 and 6.2, the extension is approved pursuant to 10 CFR 50.55a(f)(4)(iv). The use of a disassembly and inspection program for verification of the full-stroke 1
capability of these valves is approved pursuant to GL 89-04 provided all the guidance delineated in Attachment 1, Position 2, is followed.
Whether requirements are met and guidance is followed is subject to NRC inspection.
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' 2.3 Relief Reauest VR-005 The previous revision of this relief request was approved for implementation in NRC's SE dated March 11, 1992, per 10 CFR 50.55a(a)(3)(i), to conduct safety and relief valve testing in accordance with the requirements of ANSI /ASME OM-1-1991 (OM-1).
The licensee has resubmitted Relief Request VR-005 to propose that the main steam safety valves, which were not included in the scope of the previously approved relief request, also be tested in i
accordance with OM-1.
4 2.3.1 Licensee's Basis for Recuestino Relief The licensee states:
" ANSI /ASME OM-1-1981, ' Requirements for Inservice Performance Testing of Nuclear Power Plant Pressure Relief Devices,' was developed to supersede the requirements of Subsection IWV-3510. This standard is more definitive and better suited to operational testing than is ASME/PTC 25.3-1976 which is referenced in IWV-3512."
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2.3.2 Alternate Testina The licensee proposes:
" Safety and relief valves will be tested in accordance with the requirements of ANSI /ASME OM-1-1981.
During testing, the setpoint will be restored to within the specified tolerance of the original installation / construction / manufacture code before the safety / relief valve is reinstalled."
2.3.3 Additional Information Provided by the Licensee The licensee states:
"The setpoint tolerance for each main steam safety valve is 1%. This is in accordance with Technical Specification Sections 2.2.1.B and 2.2.1.D."
2.3.4 Evaluation Beginning with the 1986 Edition of ASME Section XI, OM-1 replaced ASME/PTC 25.3-1976 as the standard for safety and relief valve testing. Code Case N-415, " Alternative Rules for Testing Pressure Relief Devices,"
was approved by ASME September 5, 1985, and reaffirmed September 5, 1988.
The NRC approved the use of Code Case N-415 in Regulatory Guide 1.147,
" Inservice Inspection Code Case Acceptability ASME Section XI Division 1."
Additionally, the 1986 Edition of ASME Section XI was incorporated into 10 CFR 50.55a(b) on May 5, 1988 (53 Federal Reaister 16051) and referenced OM-1-1981. The 1989 Edition of ASME Section XI was incorporated into 10 CFR 50.55a(b) effective September 8, 1992 (see Section 1.0 above), which included the 1987 Edition of Part 1 (0M-1-1987). Therefore, the licensee may use either OM-1-1981 or 0M-1-1987 as alternative rules for safety / relief valve testing pursuant to 10 CFR 50.55a(f)(4)(iv).
The TS requirements for 11%
reset tolerance must be met.
a 2.3.5 Conclusion Because the testing will meet the requirements of later editions of the Code, relief is not required. The NRC has indicated approval of the alternative rules, and therefore, the proposed alternative is approved pursuant to 550.55a(f)(4)(iv) for use of the later editions of the Code. The licensee may implement the requirements of OM-1-1981 or 0M-1-1987 for additional safety / relief valves in the plant without further approval.
If the licensee identifies any requirements in OM-1 that are impractical for specific valves, relief from such requirements must be submitted for review and evaluation.
Principle Contributor: Joseph Colaccino i
Date: July 16, 1993 i
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