ML20044B757
| ML20044B757 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 02/24/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20044B756 | List: |
| References | |
| NUDOCS 9303030412 | |
| Download: ML20044B757 (6) | |
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,,/pomegjo UNITED STATES g
NUCLEAR REGULATORY COMMISSION e.
p WASHINGTON. D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE INSPECTION PROGRAM RELIEF RE0 VEST FOR CAROLINA POWER & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT. UNITS 1 AND 2 DOCKET NOS. 50-325 AND 50-324
1.0 INTRODUCTION
By letter dated October 9,1992, as supplemented January 27, 1993, and by letter dated December 4, 1992, Carolina Power & Light Company (CP&L) submitted several Inservice Inspection (ISI) Program relief requests for Brunswick Steam Electric Plant, Units 1 and 2 (BSEP). The first submittal was a request for relief related to the prenure testing requirements for the main steam safety /
relief valve piping for both units.
The second submittal was a request related to a modification to the Unit 2 discharge piping.
The licensee provided additional background information in a conference call on January 13, 1993.
Technical Specification 4.0.5 for BSEP states that the inservice inspection and testing of the American Society of Mechanical Engineers Code (ASME Code)
Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda, as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
Pursuant to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) may be used if (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre-service examination requirements set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations require that inservice examination of components and system pressure tests conducted during the second ten-year interval comply with the requirements in the latest Edition and Addenda of Section XI of the ASME Code incorporated by i
reference in 10 CFR 50.55a(b) on the date twelve months prior to the start of the 120-month inspection interval, subject to the limitations and modifications listed therein.
The applicable Edition of Section XI of the ASME Code for BSEP, second 10-year inservice inspection (ISI) interval, is the 1980 Edition with Addenda through Winter 1981.
The components (including supports) may meet the requirements set forth in subsequent Editions and Addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b),
subject to the limitations and modifications listed therein.
9303030412 930224 PDR ADOCK 05000324 G
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, i Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(a)(3), the staff may authorize the use of alternatives if the licensee demonstrates that (1) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality or safety.
2.0 EVALUATION 2.1 Reouest for Relief from Scheduled Pressure Test Reovirements 2.1.1 Applicable Components This request, dated October 9,1992, is applicable to the Unit 1 and 2 main steam system safety / relief valve discharge piping from valves B21-F013A through H, J, K, and L.
The main steam safety / relief valves discharge niping is classified as an ASME Code Class 3 component.
2.1.2 ASME Code Requirements ASME Section XI requires that system pressure tests and visual examinations (VT-2) be performed in accordance with subparagraph IWA-5211(b), system functional test, and IWA-5211(d), system hydrostatic test.
For the safety or relief valve piping which discharges into the containment pressure suppression pool, subparagraph IWD-5223(f) establishes the conditions for these tests, i
which is a pneumatic test (at a pressure of 90% of the piping submergence head of water) that demonstrates leakage integrity.
The system functional test is required at a 40-month frequency and the hydrostatic test is required at a j
120-month frequency.
2.1.3 Licensee's Relief Request The licensee requests approval to substitute an alternative program for the required system functional and hydrostatic tests.
2.1.4 Licensee's Basis For Request j
The discharge piping associated with the main steam system safety / relief valves is located in the drywell portion of the primary containment.
The 1
centerline of the tee-quencher for the safety / relief valve discharge l
piping is 7.25 feet below the high water level in the containment i
suppression pool.
Accordingly, the ASME Code test pressure corresponding I
to 90 percent of the pipe submergence head of water is 2.8 psi [ pounds per square inch].
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i The performance of the subject pneumatic test required by IWA-5211(b) and i
(d) testing, as permitted by the Code, would be a significant hardship l
due to the required disassembly of the discharge piping from the safety / relief valves in order to pressurize the piping for the functional or pneumatic test.
In addition, disassembly and reassembly of the safety / relief valves could result in inadvertent damage to the valve.
The system design pressure is 450 psig [ pounds per square inch gage] and the system temperature is 560*F.
The test pressure required by the ASME Code is significantly lower than the design pressure and operational pressure.
The subject pressure testing under the ASME Code does not provide assurance of the integrity of the piping and will result in personnel radiation exposure associated with performance of the test.
I Approximately 0.3 person-rem of personnel radiation exposure savings per safety / relief valve discharge line can be realized by not performing the pneumatic test in accordance with the ASME Code (i.e., a total personnel exposure savings of approximately 3.3 person-rem per unit.)
In addition, it is noted that the 1992 Edition of the ASME Section XI no longer requires the performance of the system hydrostatic test currently required by IWD-5223(f).
2.1.5 Licensee's Proposed Alternative As an alternative, at a frequency of approximately once every 18 months (in lieu of once per 40 months as required by IWA-5211(b) or once per 120 months as required by IWA-5211(d) and/or IWD-5223(f)), a periodic test i
will be performed to verify the operability of the automatic depressurization system. This alternative test involves verifying that each safety / relief valve opens by observing reactor steam flow or that l
the turbine bypass valve position indication shows a decrease.
The safety / relief valve tailpipe temperature for each safety / relief valve will be monitored to ensure a minimum increase of 20*F.
Additionally, the suppression pool is monitored for temperature changes to verify steam flow through the open ended portion of the piping.
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2.1.6 Staff Evaluation The safety / relief valve discharge piping at BSEP is constructed of 10 inch diameter or larger, schedule 80, carbon steel piping. The 2.8 psi pneumatic test permitted by ASME Code Section XI will not challenge a system that is designed for 450 psig and a system temperature of 560*F.
The ASME Code-required examir.ations will cause personnel to be subjected to significant radiation exposure. Therefore, the NRC staff concludes that the Code-required system functional tests and the hydrostatic test will result in hardship without a compensating increase in the level of quality and safety.
'l If degradation occurs in the discharge piping system, flaws must be detected by visual observation or indirect measurements.
The alternative program proposed by the licensee will periodically assess the integrity of the discharge piping system. The proposed alternative will be performed more frequently than the Code-required pressure tests.
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. The technical objective of the 2.8 psi pneumatic test is to establish the leak-tight integrity of the discharge piping. During a conference call on January 13, 1993, the licensee's staff indicated that a significant crack in the safety / relief valve discharge piping would be detected by measurements or observations. The NRC staff requests written confirmation that the licensees' alternative program has provisions for monitoring the discharge pipe in the i
suppression pool air space for leakage during the periodic test or normal operation. With this confirmatory documentation, the staff concludes that the t
licensea's proposal, described in paragraph 2.1.5 above, is superior to the Code requirement and will provide an acceptable level of quality and safety, and, therefore is acceptable pursuant to 10 CFR 50.55a(a)(3)(i).
2.2 Reauest For Relief From Pressure Test Recuirements After Modifications 2.2.1 Applicable Components The December 4, 1992, relief request applies to the Unit 2 main steam relief valve discharge piping that runs between safety / relief valve F013L and the containment suppression pool.
A portion of the piping between safety / relief valve F013L and the containment suppression pool will be removed and subsequently re-installed as shown in isometric drawing SK-EER 920438-M-2001 i
(Exhibit A to the December 4, 1992, letter).
2.2.2 ASME Code Requirement The ASME Code Section XI Article IWA-4000 provides requirements for repairs to l
pressure retaining components.
Paragraph IWA-4400(a) requires the performance of a system hydrostatic test in accordance with IWA-5000 following welding repairs.
Paragraphs IWA-5214(a) and (b) require that the pressure test l
requirements comply with IWD-5223 for Class 3 components.
Paragraph IWD-5223(f) permits a pneumatic test (at a pressure of 90 percent of the pipe j
submergence head of water) for safety or relief valve piping which discharges into the containment pressure suppression pool in lieu of a system hydrostatic l
test.
i 2.2.3 Licensee's Relief Request i
n The licensee requests approval to substitute radiography as an alternative to l
the required hydrostatic test.
l 2.2.4 Licenseo's Basis For Request
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l A condition has been identified where, due to thermal expansion, the discharge piping for the F013L main steau safety / relief valve makes physical contact with a line associated with drywell spray. A plant modification is needed to re-route portions of the discharge line for the F013L main steam safety / relief valve.
To support the modification, a i
portion of the discharge piping for the F013L main steam safety / relief l
valve will be temporarily removed, reconfigured, and subsequently re-installed as shown in the... isometric drawing from the Engineering Evaluation Report (Exhibit A).
The affected discharge piping is located in the drywell portion of the primary containment.
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-E-As described above, subparagraph IWD-5223(f) of the ASME Code,Section XI t
requires a pneumatic test at a pressure of 90 percent of the pipe submergence head of water (i.e.
2.8 psi). The centerline of the tee-quencher for the relief valve discharge piping is 7.25 feet below the high water level in the containment suppression pool. Therefore, the test pressure corresponding to 90 percent of the pipe submergence head of water, as required by the ASME Code,Section XI, subparagraph IWD-5223(f), is 2.8 psi.
t Performance of the pneumatic pressure test will require disassembly of the F013L safety / relief valve in order to pressurize the piping to the i
2.8 psi test pressure and perform the examination.
The design pressure and temperature for the piping is 450 psig and 560 degrees F.
The test pressure required by IWD-5223(f) (i.e., 2.8 psi) is significantly lower than the design pressure of the piping and the operating pressure typically experienced by the piping; therefore, the Company does not believe the IWD-5223(f) test provides assurance of the integrity of the piping.
In addition, the potential exists for inadvertently damaging the i
F013L safety / relief valve during the performance of the test. Therefore, the Company believes the test requirement is impractical and requests relief in accordance with 10 CFR 50.55a(g).
2.2.5 Licensee's Proposed Alternative The field welds will be examined to the most stringent optional requirement of the ASME Code,Section III, Class 3 (i.e., using RT
[ radiographic testing] examination). Based on the alternative testing,
-L it is highly improbable that a weld that passes a volumetric examination
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will leak at a test pressure of 2.8 psi (a test pressure of 90 percent of the pipe submergence head of water).
l 2.2.6 Staff Evaluation i
The original and new discharge piping between safety / relief valve F013L and the containment suppression pool is 10-inch diameter, schedule 80, carbon steel piping. The 2.8 psi pneumatic test permitted by ASME Code Section XI will not challenge a repair by welding in a system that-is designed for 450 psig and a system temperature of 560*F.
Since performance of the pneumatic pressure test will require disassembly of the F013L safety / relief valve in order to perform the examination, and since this test will not challenge the repair, the' staff agrees with the licensee that the Code-required pneumatic test will result in hardship without a compensating increase in the level of-quality and safety.
As an alternative the licensee proposes to perform radiography on.the field welds based on the ASME Code,Section III. The NRC staff concludes that the licensee's proposal to use radiography is equivalent or superior to the-examination method used during the original construction of similar ASME Code Class 3 piping welds.
For this reason, the staff concludes that the licensee's proposal to radiograph the field welds-is superior to the Code-required pneumatic test and will provide an acceptable level of quality and safety, and, therefore is acceptable pursuant to 10 CFR 50.55a(a)(3)(i).
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3.0 CONCLUSION
In evaluating the licensee's requests for relief from the requirements of Section XI, the staff considered (1) the acceptability of proposed alternative testing, (2) whether the hardship of compliance is without a compensating increase in safety, and (3) the impracticality of performing the required testing considering the burden if the requirements were impcsed.
The staff concludes that the two alternative programs proposed by the licensee are superior to the Code-required pressure tests and, therefore, are acceptable pursuant to 10 CfR 50.55a(a)(3)(i). This finding is subject to submittal of confirmatory information as identified above.
Principal Contributor:
M. Hum Date:
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