ML18101A529
| ML18101A529 | |
| Person / Time | |
|---|---|
| Site: | Salem, Hope Creek  |
| Issue date: | 01/20/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18101A527 | List: |
| References | |
| NUDOCS 9502080317 | |
| Download: ML18101A529 (5) | |
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I UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO A REQUEST TO USE AN ALTERNATIVE TO ASME CODE SECTION XI PUBLIC SERVICE ELECTRIC AND GAS COMPANY SALEM NUCLEAR GENERATING STATION. UNITS I AND 2. AND HOPE CREEK GENERATING STATION DOCKET NOS. 50-272. 50-3II. 50-354 I.O INTRODUCTION The Technical Specifications for the Salem Nuclear Generating, Station, Units I and 2, and Hope Creek Generating Station, state that the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class I, 2, and 3 components shall be performed in accordance w1th Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by IO CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to IO CFR 50.55a(g)(6)(i). The Code of Federal Regulations at IO CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, 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 IO CFR 50.55a(g)(4), ASME Code Class I, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice 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 first IO-year inspection interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in IO CFR 50.55a(b) on the date I2 months prior to the start of the I20-month interval, subject to the limitations and modifications listed therein.
The applicable edition of Section XI of the ASME Code for:
(I) Salem, Unit I, Second IO-year inservice inspection (ISi) interval is the I983 Edition with the Summer I983 Addenda, (2) Salem 2, second IO-year ISI interval is the I986 Edition, and (3) Hope Creek, first IO-year ISI interval is the I983 Edition with the Summer I983 Addenda.
9502080317 950120 PDR ADOCK 05000272 P
I I. Public Service Electric and Gas Company (PSE&G) requested approval to use an alternative to the American Society of Mechanical Engineers (ASME) Code Section XI pursuant to the provisions of 10 CFR 50.55a(a)(3). Specifically, PSE&G, the licensee for Salem and Hope Creek, requested approval to use the provisions of Code Case N-416-1, "Alternative Pressure Test Requirements for Welded Repairs or Installation of Replacement Items by Welding, Class l, 2, and 3,Section XI, Division 1."
2.0 EVALUATION OF CODE CASE N-416-1. "ALTERNATIVE PRESSURE TEST REQUIREMENT
-FOR WELDED REPAIRS OR INSTALLATION OF REPLACEMENT ITEMS BY WELDING CLASS
- 1. 2. and 3 - SECTION XI. DIVISION 1" Plants Covered Salem Nuclear Generating Station, Units 1 and 2, and Hope Creek.Generating Station Component Identification ASME Class 1, 2, and 3 Piping Systems ASME Code Section XI Reguirements.
Section XI, paragraph IWA-4700(a) requires that a system hydrostatic test be performed in accordance with paragraph IWA-5000 after repairs by welding on the pressure retaining boundary.
Proposed Alternative Examination The licensee proposes to apply Code Case N-416-1 as alternative rules for welded repairs or installation of replacement items by welding in Class 1, 2, and 3 piping.
Licensee's Basis for Reguest "Numerous benefits are gained by use of this Code Case.
Among all three units, approximately 100 to 150 hydrostatic tests are conducted annually.
It is estimated that approximately 20 person-days time is expended for set-up, testing, disassembly, and system restoration for the 'average' hydrostatic test.
In addition, approximately five to six days are expended for the conduct of each typical hydrostatic test. Significant labor is expended, which results is [in] very little or no added safety benefit, and generally, these tests are performed during refueling outages, often as critical path activities.
"By not having to conduct the additional efforts associated with testing lineup, test system disassembly, and system restoration, the system availability for operation is accelerated, and overall job labor and person-rem exposure is reduced, the Use of Code Case N-416-1, through the elimination of the added work, substantially reduces resource and time demands placed upon station organizations and contributes to ALARA practices."
Evaluation In lieu of hydrostatic pressure testing for welded repairs or installation of replacement items by welding, Code Case N-416-1 requires a visual examination (VT-2) be performed in conjunction with a system leakage testing using the 1992 Edition of Section XI, in accordance with paragraph IWA-5000, at nominal operating pressure and temperature. This Code Case also specifies that non-destructive examination (NOE) of the welds be performed in accordance with the applicable Subsection of the 1992 Edition of Section III.
The 1989 Edition of Sections XI and III are the latest editions referenced in IO CFR 50.55a.
The staff has compared the system pressure test requirements of the 1992 Edition of Section XI to the requirements of paragraph IWA-5000 of the 1989 Edition of Section XI.
In summary, the 1992 Edition imposes a more uniform set of system pressure test requirements for Code Class I, 2, and 3 systems.
The terminology associated with the system pressure test requirements for all three Code classes has been clarified and streamlined.
The test frequency and test pressure conditions associated with these tests has not been changed.
The hold times for these tests has either remained unchanged or increased.
The corrective actions with respect to removal of bolts from leaking bolted connections has been relaxed in the 1992 Edition, but use of this change has been accepted by the staff in previous safety evaluations.
The post-welded repair NOE requirements of the 1992 Edition of Section III remain the same as the requirements of the 1989 Edition of Section III. Therefore, the staff finds this aspect of Code Case N-416-1 to be acceptable.
Hardships are generally encountered with the performance of hydrostatic testing performed in accordance with the Code.
For example, since hydrostatic test pressure would be higher than nominal operating pressure, hydrostatic.
pressure testing frequently requires significant effort to set up and perform.
The need to use special equipment, such as temporary attachment of test pumps and gages, and the need for individual valve lineups can cause the testing to be on critical path.
Piping components are designed for a number of loadings that would be postulated to occur under the various modes of plant operation. Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure and, therefore, does not present a significant challenge to pressure boundary integrity. Accordingly, hydrostatic pressure testing is primarily regarded as a means to enhance leakage detection during the examination of component-s under pressure, rather-than solely as a measure -
to determine the structural integrity of the components.
The industry indicates that experience has demonstrated that leaks are not being discovered as a result of hydrostatic test pressures propagating a preexisting flaw through wall.
They indicate that, when leaks are found, in most cases they are found when the system is at normal operating pressure.
This is largely due to the fact that hydrostatic pressure testing is required only upon installation and then once every IO-year inspection interval, while system leakage tests at nominal operating pressures are conducted a minimum of once each refueling outage for Class I systems and each 40-month inspection period for Class 2 and 3 systems.
In addition, leaks may be identified by plant operators during system walkdowns which may be conducted as often as once a shift.
Following the performance of welding, the Code requires volumetric examination of repairs or replacements in Code Class I and 2, but only requires a surface examination of the final weld pass in Code Class 3 piping components.
There are no ongoing NDE requirements for Code Class 3 components except for visual examination for leaks in conjunction with the IO-year hydrostatic tests and the periodic pressure tests.
Considering the NDE performed on Code Class I and 2 systems and considering that the hydrostatic pressure tests rar~ly result in pressure boundary leaks that would not occur during system leakage tests, the staff believes that increased assurance of the integrity of Class I and 2 welds is not commensurate with the burden of performing hydrostatic testing. However, considering the nature of NDE requirements for Code Class 3 components, the staff does not believe that eliminating the hydrostatic pressure testing and only performing system pressure testing is an acceptable alternative to hydrostatic testi~g unless additio~al surface examinations are performed on the root pass layer of butt and socket welds on the pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with Section III.
With this provision applied to Code Class 3 components, the staff concludes that compliance with th.e Code hydrostatic testing requirements for welded repairs or replacements of Code Class 1, 2, and 3 components would result in hardships without a compensating increase in the level of quality and safety.
Accordingly the licensee's proposed alternative to use Code Case N-416-1 is authorized for Salem and Hope Creek, pursuant to 10 CFR 50.55a(a)(3)(ii),
provided additional surface examinations are performed on the root pass layer of butt and socket welds on the pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with Section III.
Use of Code Case N-416-1, with provision as noted above, is authorized until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee is to follow all provisions in Code Case N-416-1, with limitations issued in Regulatory Guide 1.147, if any.
3.0 CONCLUSION
The staff evaluated the information provided by the licensee for Salem and Hope Creek in support of their request to use an alternative to the ASME Code pursuant to the provisions of 10 CFR 50.55a(a)(3).
Based on the information submitted, the alternatives are authorized pursuant to 10 CFR 50.55a(a)(3)(ii) as compliance with the ASME Code Section XI hydrostatic testing requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Principal Contributors:
C. Battige L. Olshan Date:
January 20, 1995