ML20128E410
| ML20128E410 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 12/01/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20128E385 | List: |
| References | |
| NUDOCS 9212080082 | |
| Download: ML20128E410 (5) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FIRST TEN-YEAR INTERVAL INSERVICE INSPECTION REllEF RE0 VEST NOS. 22 AND 23 f_Q3 COMMONWEALTH EDIS0N COMPANY LASALLE COUNTY STATION. UNITS 1 AND 2 DOCKET NOS. 50-373 and 50-374
1.0 INTRODUCTION
The Technical Specifications for the LaSalle County Station, Units 1 and 2, state that inservice inspection and testing of American Society of Mechan _ical Engineers (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).
Paragraph 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (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 and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservin 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 first ten-year interval comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date twelve months prior to.the start of
'1 the 120-month inspection interval, subject to the limitations ind modifications-listed therein.
The applicable edition of Section XI of the ASME Code for.the LaSalle County Station, (LaSalle) Inservice Inspection (ISI) Program is the 1980 Edition.
through 1980 Winter Addenda.
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.
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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, the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life or property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
In a letter dated May 7,1992, Commonwealth Edison Company, the licensee, submitted Relief Requests RI-22 and RI-23 asking for relief from the hydrostatic testing after the replacement of components during the fifth refueling outage.
The subject requests are applicable to both units.
The licensee requested that the relief extend through the remainder of the first 10-year inspection interval, which will be completed after each unit's sixth refueling outage.
The staff has evaluated the requests in the section that follows.
The ASME has published Code Case N-416 that is relevant to the licensee's request.
2.0 EVALUATION The information provided by the licensee in support of the request for relief has been evaluated and documented below.
2.1 RE0 VEST FOR RELIEF NO. RI-22 RELATED TO THE REACTOR CORE ISOLATION COOLING (RCIC) SYSTEM STEAM SUPPLY INBOARD ISOLATION VALVES-(IE51-F063 IN URJLijsND 2E51-F063 IN UNIT 21 2.1.1 Code Reauinen1: The request involves circumferential welds in pressure retaining piping greater than-or equal to 4 inches in diameter.
Articles IWA-7000 and IWB-7000 govern the replacement of these system valves.
The referenced articles require the performance of a hydrostatic test after the replacement is completed in accordance with Paragraph IWA-5214 and Subparagraph IWB-5222(a).
IWB-5222(a)_ states that the system hydrostatic _ test shall be conducted at a test ' pressure 1.10 times the system nominal operating pressure that corresponds with 100% rated reactor power except when the test is conducted at temperatures above 100 degrees Fahrenheit to meet the requirements of IWB-5230.
2.1.2 Licensee's Code Relief Reouest: The licensee proposes to perform the System Leakage Test as described in Subparagraph IWA-5211(a), and Paragraph-IWB-5221. This proposed alternative pres:ure test shall be conducted at a _ test pressure not less than the nominal operating pressure associated with-100% rated reactor power.
2.1.3 Licensee's Basis for Reouestino Relief:
Due to the physical location of the replacement _ valve (s) in the piping system, LaSalle Station'is. unable to provide a practical upstream hydrostatic test boundary between the
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replacement valve (s) and the. reactor pressure vessel.
The inability to provide such an isolation boundary would result in undue hardship, and difficulty in that'a hydrostatic test of the reactor pressure vessel would be required in order to meet the Code specified examination.
The valve lineup associated with the hydrostatic test of the reactor pressure vessel would require that certain safety system components such as the main steam safety relief valves be gagged, and that other overpressure protection devices and instruments be defeated in order to prevent their actuation during the test.
The technical basis for requesting relief from the Code requirement is supported by the fact that the replacement valve (s) will be constructed in accordance with ASME Section III Class 1 rules which require that the completed component be hydrostatically tested at the manufacturer's shop.
The weldments which join the new replacement valve (s) component to the connecting piping will also be required to meet ASME Section III, Class I standards and will, therefore, be subjected to both surface and volumetric examination.
Upon completion of the construction phase of the replacement, additional volumetric examination using the ultrasonic method will be performed to meet the preservice inspection requirements of the 1980 Edition, Winter 1980 Addenda of ASME Section XI.
It is the belief of LaSalle County Station that this level of nondestructive examination, when combined with the proposed alternative examination described above, gives adequate assurance that the structural integrity of the system has been maintained, as well as providing the appropriate level of quality and safety.
2,1.4 Aonlicable Time Period Reauested by the licensee: This relief is requested for each refueling outage for LaSalle County Station Units 1 & 2, beginning with the fifth refueling outage for Unit I which is scheduled to begin September 26, 1992.
It is also requested that the relief extend through the remainder of the first 10-year inspection interval for each Unit (l&2) which will be completed after that Unit's sixth refueling outage. The sixth refueling outage for LaSalle. County Station Unit -1 is scheduled to end in May of.1994. The sixth refueling outage for.LaSalle County Station Unit 2 is scheduled to end in May of 1995.
Extension of the relief for these specific applications (replacement of the 1&2E51-F063 valves) through the end of-the inspection interval would alleviate the need to generate an additional relief request if installation of the subject design changes were deferred from the upcoming fifth refueling outage (s) due to uncertainty in scheduling.
2.1.5 Staff Evaluation:
The staff has determined that the Code required hydrostatic test of the subject RCIC system valves is impractical-to perform.
The reactor coolant pressure boundary would have to be redesigned to provide isolation valves.
In its.present configuration, the Code would require subjecting the reactor vessel to the hydrostatic test conditions. Accordingly, relief is granted as requested pursuant to 10 CFR 50.55a(g)(6)(i).
Additionally, on May 13, 1991, the ASME Council approved Code Case N-416
" Alternative Rules for Hydrostatic Testing of Repair or Realacement of Class 2 Piping" for ASME Section XI.
Code Case N-416 has seen referenced in Regulatory Guide 1.147. The primary conclusion of the ASME for Class 2 piping was that a volumetric examination for full penetration welds and a visual examination for leakage is a suitable alternative to the hydrostatic test when the system cannot be isolated by existing valves.
The staff determined as part of 'Ms evaluation that the provisions of Code Can N-416 is a suitable ab ernative for the n'uject t. lass 1 RCIC valves. The staff also finds that the nondestructive examinattun described in the licensee's letter is equivalent or superior to the provisions of Code Case N-416.
Therefore, the combination of nondestructive examinations and system leakage tests proposed by the licensee will provide adequate assurance of the structural integrity of the repair /replamament components.
2.2 REQUEST FOR REllEF N0. RI-23 RELATED TO THE RCIC SYSTEM HEAD SPRAY PIPING FOR BOTH UNITS 2.2.1 Code Reauirements:
The request involves circumferential welds in pressure retaining piping greater than or equal to 4 inches in diameter.
Articles IWA-7000 and IWB-7000 govern the replacement of a portion of the RCIC system head spray piping for Units 1 & 2 in the vicinity of the connection of this piping to the reactor pressure vessel head spray nozzle (N-7).
Specifically, the licensee plans to replace a section of the head spray piping with mating flanges.
The referenced articles that require the performance of a hydrostatic test in accordance with Paragraph IWA-5214 and Subparagraph IWB-5222(a) which state that the system hydrostatic test shall be conducted at a test pressure 1.10 times the system nominal operating pressure that corresponds with 100% rated reactor power except when the test is conducted at temperatures above 100 degrees Fahrenheit (38'C) to meet the requirements of IWB-5230.
2.2.2 Licensee's Code Relief Recuest: The licensee's proposal is the same as paragraph 2.1.2 for the RCIC steam supply inboard isolation valves.
2.2.3 Licensee's Basis for Reauestino Relief:
The licensee's basis is the same as paragraph 2.1.3.
2.2.4 Applicable Time Period Reouested by the licensee:
The licensee requests that the applicable time period be the same as paragraph 2.1.4.
2.2.5 STAFF EVALUATION The mating flanges are to be welded onto the RCIC piping.
Similar to the replacement valves described in Section 2.1, the location of the mating flanges makes it impractical to provide an upstream hydrostatic test boundary between the flanges and the reactor ~ pressure vessel. To avoid subjecting the reactor vessel to hydrostatic test conditions would require redesigning the reactor coolant pressure boundary, and conducting the ASME Code required hydrostatic test after the flanges are l
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.5-installed would also require disabling certain safety system components such as overpressure protection devices, to prevent their actuation during the test.
Accordingly, relief is granted as requested pursuant to 10 CFR 50.55a(g)(6)(i).
Additionally, on May 13, 1991, the ASME Council approved Code Case N-416
" Alternative Rules for Hydrostatic Testing of Repair or Realacement of Class 2 Piping" for ASME Section XI.
Code Case N-416 has seen referenced in Regulatory Guide 1.147.
The primary conclusion of the ASME for Class 2 piping was that a volumetric examination for full penetration welds and a visual examination for leakage is a suitable alternative to the hydrostatic test when the system cannot be isolated by existing valves. The staff determined as part of this evaluation that the provisions of Code Case N-416 is a suitable alternative for the subject Class 1 RCIC system piping.
The staff also finds that the nondestructive examination described in the licensee's letter is equivalent or superior to the provisions of Code Case N-416. Therefore, the combination of nondestructive examinations and system leakage tests proposed by the licensee will provide adequate assurance of the structural integrity of the replacement components.
3.0 CONCLUSION
S The ASME has published Code Case N-416 that is relevant to the licensee's letter.
In Code Case N-416, the ASME provides guidance for the substitution of nondestructive examination for the hydrostatic test of Class 2 piping.
The staf f agrees that perfc,rming nondestructive examinations that are equivalent or superior to the examinations performed during original construction will provide reasonable assurance of the structural integrity of Class 1, 2 and 3 piping system welds.
Regarding the licensee's relief request numbers RI-22 and RI-23, paragraph 10 CFR 50.55a(g)(4) requires that components (including supports) that are classified as ASME Code Class 1, 2, and 3 meet the requirements, except the design and access provisions and preservice requirements, set forth in applicable editions of ASME Section XI to the extent practical-within the limitation of design, geometry, and materials of construction.of the components.
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee determined that conformance with a Code requirement is impractical for this facility and submitted supporting technical justification.
Pursuant to 10 CFR 50.55a(g)(6)(1), the staff has determined that the applicable requirement of the Code is impractical for laSalle County Station, Units 1 and 2, and relief may be granted based on the information described herein.
This evaluation gives'due consideration to the burden upon the licensee that could result _if the _ requirements were imposed on the facility.
Such relief and alternative-examinations are authorized by law, will not endanger life, property, or the common defense _and security, and an otherwise in the public interest.
Principal Contributor: M. Hum, EMCB Date: December 1. 1992
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