ML18152B648
| ML18152B648 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/14/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML18152B647 | List: |
| References | |
| NUDOCS 9904160224 | |
| Download: ML18152B648 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555--0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF NOS. IWE-2, 4, 5, 6 AND IWL-2 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-280 AND 50-281
1.0 INTRODUCTION
In a Federal Register (FR) notice dated August 8, 1996 (61 FR 41303), the Nuclear Regulatory Commission announced the am~ndment to its regulation, Title 1 O of the Code of Federal Regulations (1 O CFR) Section 50.55a (rule). The rule incorporated by reference the 1992 edition with 1992 addenda of Subsections IWE and IWL of Section XI of the American Society
- of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code). Subsections IWE and IWL provide the requirements for inservice inspection (ISi) of Class CC (concrete containments), and Class MC (metallic containments) of light-water cooled power plants. The effective date for the amended rule was September 9, 1996, and it requires the licensees to incorporate the new requirements into their ISi plans and to complete the first containment inspection by September 9, 2001. However, a licensee can submit a request for relief (RR) from one or more requirements of the regulation (or the endorsed Code requirements) with proper justification. The provision for granting relief is incorporated in the regulation.
This evaluation addresses the RR proposed by the licensee, Virginia Electric and Power Company, in a letter dated August 28, 1998, for its Surry Nuclear Power Station, Units 1 and 2.
2.0 EVALUATION Relief Request IWE-2 Code Requirement(s) and Relief Request IWE-2500, Table IWE-2500-1 requires seals and gaskets on airlocks, hatches, and other devices to be visually examined, using the VT-3 procedure, once each interval to assure containment leaktight integrity. Relief is requested from performing the Code-required visual examination, VT-3, on the above identified metal containment seals and gaskets.
Basis for Relief Section 50.55a was amended, as cited in the Federal Register (61 FR 41303), to require the use of the 1992 Edition, 1992 Addenda of Section XI when performing containment examinations. The penetrations discussed below contain seals and gaskets:
Enclosure A..
Electrical Penetrations Electrical penetrations use a header plate attached to a containment penetration nozzle flange with redundant 0-rings between the header plate and flange face. Modules through which electrical conductors pass are installed in the header plate and flange face.* One type, manufactured by Amphenol, uses seals and gaskets to assure leaktight integrity. A second type, manufactured by Conax, uses a set of compression fittings.
Replacement modules for the Amphenol penetrations use a combination of 0-rings and compression fittings. These seals and gaskets cannot be inspected without disassembly of the penetration to gain access to the seals and gaskets.
B.
Containment Personnel, Equipment, and Emergency Escape Hatches The Personnel, Equipment, and Emergency Escape Hatches utilize an inner and outer door with gasketed surfaces to ensure a leaktight integrity. These hatches also contain other gaskets and seals such as electrical penetrations and equalizing pressure connections that require disassembly to gain access to the gaskets and seals.
C.
Fuel Transfer TLJbe The fuel transfer tube utilizes a blank flange inside containment with redundant 0-rings between the header plate and flange face.
In accordance with 1 O CFR Part 50, Appendix J, seals and gaskets receive a Type B test. As noted in 10 CFR.Part 50 Appendix J, the purpose of Type B tests is to measure leakage of containment or penetrations whose design incorporates resilient seals, gaskets, sealant compounds, and electrical penetrations fitted with flexible metal seal assemblies. For those penetrations that are routinely disassembled, a Type B test is required upon final assembly and prior to start-up. For those penetrations that are not routinely disassembled, Table IWE-2500-1, Category E-D, Note 1 (1993 Addenda and later) states that "Sealed or gasketed connections need not be disassembled solely for the purpose of examination." Therefore, these seals and gaskets would not be visually examined.
Table IWE-2500-1, Category E-P, Item E9.40, requires performance of an Appendix J Type B test for seals and gaskets. Since the Type B test will assure the leaktight integrity of primary containment at the same frequency as that of the Code visual exams, the performance of the visual examination is redundant and will not increase the level of safety or quality.
Relief is requested in accordance with 1 O CFR 50.55a(a)(3)(ii). Compliance with the visual examination of seals and gaskets in accordance with IWE-2500, Table IWE-2500-1, Category E-D is a burden without any compensating increase in the level of quality and safety.
Visual examination of seals and gaskets will not ensure leaktight integrity. Testing the seals and gaskets in accordance with 1 O CFR Part 50, Appendix J, will provide adequate assurance of the leaktight integrity of the seals and gaskets. Implementing an ASME Section XI Code program to perform these examinations is an unnecessary administrative burden. Testing the seals and gaskets in accordance with 1 O CFR Part 50, Appendix J, is superior to performing a visual examination and provides assurance of the leaktight integrity of the ~eals and gaskets.
The Appendix J testing frequency is greater than that of ASME Section XI and, therefore, is
e more conservative and provides a greater level of safety. Appendix J testing is a superior method of establishing seal integrity.
Alternative Examination(s)
The leaktightness of seals and gaskets will be tested in accordance with 1 O CFR Part 50, Appendix J. The 10 CFR Part 50, Appendix J, Type B testing is performed at least once each inspection interval.
Staff Evaluation of RR-IWE-2 The staff agrees that the licensee's alternative examination commitment of functionality of the containment penetration seals and gaskets (including those of electrical penetrations and fuel transfer tubes) would be verified during the Type B testing as required by 1 O CFR Part 50, Appendix J. The staff also agrees with the licensee that the 1 O CFR Part 50, Appendix J, testing is a superior alternative method of establishing seal integrity. The staff further agrees with the licensee that compliance with the ASME Section XI Code program would result in
- hardship or unusual difficulty without a compensating increase in the level of quality and grants relief under 1 O CFR 50.55a(a)(3)(ii).
Relief Request RR-IWE-4 Code Requirement(s) and Relief Request Paragraphs IWE-2420(b) and IWE-2420(c) of the 1992 Edition, 1992 Addenda of ASME Section XI require that when component examination results require evaluation of flaws, evaluation of areas of degradation, or repairs in accordance with Article IWE-3000, "Acceptance Standards," and the component is found to be acceptable for continued service, the areas containing such flaws, degradation, or repairs shaU be reexamined during the next inspection period listed in the schedule of the inspection program of Paragraph IWE-2411, "Inspection Program A," or Paragraph IWE-2412, "Inspection Program B," in accordance with Table IWE-2500-1, Examination Category E-C. Relief is requested froni the requirement of Paragraphs IWE-2420(b) and IWE-2420(c) to perform successive examination of repairs.
Basis for Relief Section 50.55a was amended, as cited in the Federal Register (61 FR 41303), to require the use of the 1992 Edition, 1992 Addenda, of Section XI, when performing containment examinations. The purpose of a repair is to restore the component to an acceptable condition for continued service in accordance with the acceptance standards of Article IWE-3000.
Paragraph IWA-4150, "Verification of Acceptability," requires the owner to conduct an evaluation of the suitability of the repair including consideration of the cause of failure.
If the repair has restored the component to an acceptable condition, successive examinations are not warranted. If the repair was not suitable, then the repair does not meet Code requirements and the component is not acceptable for continued service. Neither Paragraph IWB-2420(b), Paragraph IWC-2420{b), nor Paragraph IWD-2420(b) requires a repair to be subject to successive examination requirements. Furthermore, if the repair area is subject to accelerated degradation, it would still require augmented examination in accordance with Table IWE-2500-1, Examination Category E-C. The successive examination of repairs in accordance with Paragraphs IWE-2420(b} and IWE-2420(c) constitutes a burden without a compensating increase in quality or safety.
In SECY 96-080, "Issuance of Final Amendment to 10 CFR Section 50.55a to Incorporate by Reference the ASME Boiler and Pressure Vessel Code (ASME Code),Section XI, Division 1, Subsection IWE and Subsection IWL," dated April 17, 1996, response to comment# 3.3 states, "The purpose of IWE-2420(b) is to manage components found to be acceptable for continued service (meaning no repair or replacement at this time) as an Examination Category E-C component. If the component had been repaired or replaced, then the more frequent examination would not be needed."
Relief is requested in accordance with 1 Q CFR 50.55a(a)(3)(ii). Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Alternate Examination(s)
Successive examinations in accordance with Paragraphs IWE-2420(b) and IWE-2420(c) are not required for repairs made in accordance with Article IWA-4000.
Staff Evaluation of RR-IWE-4 The staff agrees with the licensee that successive examinations after repair do not provide additional. safety benefit. This position has been accepted by the staff for Class 1, 2
- and 3 components. Therefore, considering the hardship associated with the 1992 Edition ASME Code requirements IWE-2420(b) and 2420(c), the staff grants that relief from the Code requirements pursuant to 1 O CFR 50.55a(a)(3)(ii).
Relief Request RR-IWE-5 Code Requirement(s) and Relief Request ASME Section XI, 1992 Edition with the 1992 Addenda, Table IWE-2500-1, Examination Category E-G, Pressure Retaining Bolting, Item 8.20, requires a bolt torque or tension test on bolted connections that have not been disassembled and reassembled during the inspection interval. Relief is requested from ASME Section XI 1992 Edition with the 1992 Addenda, Table IWE-2500-1 Examination Category E-G, Pressure Retaining Bolting, Item 8.20.
Basis for Relief Section 50.55a was amended, as cited in the Federal Register (61 FR 41303), to require the use of the 1992 Edition, 1992 Addenda, of ASME Section XI when performing containment examinations. Bolt torque or tension testing is required on bolted connections that have not been disassembled and reassembled during the inspection interval. Determination of the torque or tension value would require that the bolting be un-torqued and then retorqued or retensioned.
,,. Each containment penetration receives a 10 CFR Part 50, Appendix J, Type B test in accordance with the specified testing frequencies. As noted in 1 O CFR Part 50, Appendix J, the purpose of Type B tests is to measure leakage of containment penetrations whose design
. incorporates resilient seals, gaskets, sealant compounds, and electrical penetrations fitted with flexible metal seal assemblies. The performance of the Type B test itself proves that the bolt torque or tension remains adequate to provide a leak rate that is within acceptable limits. The torque or tension value of bolting only.becomes an issue if the leak rate is excessive.
Appendix J testing and visual inspection is adequate to demonstrate that the design function is met. Torque or tension testing is not required for any other ASME Section XI, Class 1, 2, or 3 bolted connections or their supports as part of the ISi program.
Relief is requested in accordance with 10 CFR 50.55a(a)(3}(ii). Untorquing and subsequent re-torquing of bolted connections which are verified not to experience unacceptable leakage through 10 CFR Part 50, Appendix J, Type B testing results in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Alternate Examination(s)
The following examinations and tests required by Subsection IWE ensure the structural integrity and the leaktightness of Class MC pressure-retaining bolting, and therefore, no additional alternative examinations are proposed:
- (1) Exposed surfaces of bolted connections shall be visually examined in accordance witb requirements of Table IWE-2500-1, Examination Category E-G, Pressure Retaining Bolting, Item No. E8.10, and (2) Bolted connections shall meet the pressure test requirements of Table IWE-2500-1, Examination Category E-P, All Pressure Retaining Components, Item E9.40.
Staff Evaluation of RR-IWE-5 The staff agrees with the licensee's contention that the torque or tension testing of bolts during IWE examination, when the bolted connections are not disassembled, will result in hardship without a commensurate increase in the level of safety or quality. The staff finds that the alternatives proposed by the licensee are acceptable, and grants relief pursuant to 1 O CFR 50.55a(a)(3)(ii).
Relief Request RR-IWE-6 Code Requirements and Relief Request ASME Section XI, 1992 Edition, 1992 Addenda, Subarticle IWE-2500(c)(3) requires one-foot
- square grids be used when ultrasonic thickness measurements are performed on augmented examination surface areas. The number and location of the grids is determined by the Owner.
Subarticle IWE-2500(c)(4) requires that the minimum wall thickness within each grid be determined. Relief is requested from using one-foot square grids for augmented examination areas and the requirement to determine the minimum wall thickness within each grid.
e Basis for Relief Subarticles IWE-2500(c)(3) and IWE-2500(c)(4) of the 1992 Edition, 1992 Addenda of ASME Section XI require that the minimum thickness within each one-foot square grid of surface areas requiring augmented examination be marked such that periodic reexamination of that location can be performed. Thickness readings are point readings. Numerous readings are necessary to identify the location of minimum thickness within each grid. This only identifies the thinnest area. Periodic examination of the minimum thickness point only monitors that point. It may not be the area that is the most susceptible to accelerated degradation.
Table RR-IWE-6, "Ultrasonic Thickness Measurements for Augmented Examination," provides the proposed alternative to the one-foot square grid area required by IWE-2500(c)(3). Table RR-IWE-6 requires examination at the grid line intersections. The grid line intersections may
- not exceed 12 inches and may be as small as 2 inches.
For a sample area of 50 square feet, Table RR-IWE-6 requires a minimum 100 locations be monitored. For a sample area of 50 square feet, IWE-2500(c)(3) would require only 50 locations be monitored. In this instance, utilizing Table RR-IWE-6 monitors more locations than required by IWE-2500(c)(3).
For sample areas greater than 100 square feet, Table RR-IWE-6 requires that sufficient points be monitored to ensure at least a 95 percent confidence level that the thickness of the base metal is reduced by no more than 1 O percent of the nominal plate thickness at 95 percent of the grid line intersections. Table RR-IWE-6 also requires additional examinations when any measurements reveal wall thickness is reduced by more than 1 O percent of the nominal plate thickness.
For all examination areas, should the measurements at a grid line intersection reveal that the base material is reduced by more than 10 percent of the nominal plate thickness, Table RR-IWE-6 requires the minimum wall thickness within each adjoining grid be determined. This is similar to the examination requirements of IWE-2500(c)(4) except that Table RR-IWE-6 focuses resources on areas which have exhibited degradation rather than areas which have not exhibited degradation.
The Flow Accelerated Corrosion programs presently in place have proven that taking thickness readings at grid intersections are effective in monitoring wall thinning of piping.
Relief is requested in accordance with 1 O CFR 50.55a(a)(3)(ii). Taking numerous ultrasonic thickness readings within a grid which had not exhibited degradation results in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Alternative Examination(s)
Table RR-IWE-6 will be used to determine examination requirements for ultrasonic thickness measurements of areas requiring augmented examination.
Staff Evaluation of RR-IWE-6 A review of Table RR-IWE-6 indicates that the alterative examination proposed by the licensee is at least as good as the Code requirements in IWE-2500(c)(3) and IWE-2500{c)(4). The staff agrees with the licensee that taking numerous ultrasonic thickness readings within a grid which has not exhibited degradation results in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The staff grants relief pursuant to 1 O CFR 50.55a(a)(3)(ii).
Relief Request RR-IWL-2 Code Requirements and Relief Request Subarticle IWA-2210 provides requirements for visual examination procedures. Relief is requested from the provisions of Table IWA-2210-1, Visual Examinations. Table IWA-2210-1 requires direct visual VT-3 examinations be performed with a minimum illumination of 50 fc and at a maximum examination distance of 4 feet. The procedure must be demonstrated to resolve a lower case character height of 0.105 inches.
Basis for Relief In addition to the requirements of Subsection IWL, the requirements of the 1992 Edition, 1992 Addenda of Subsection IWA for containment examinations are applicable.
For VT-3C examination performed in accordance with Subsection IWL, the examination distance and illumination requirements are the same as those specified for VT-3C in Table IWA-2210-1. For remote examination of IWE components, 1 o CFR 50.55a permits the maximum direct examination distance specified in Table 'IWA-2210-1 be extended and the minimum illumination requirements specified in Table IWA-2210-1 decreased provided that the*
conditions or indications for which the visual examination is performed can be detected at the chosen distance and illumination. This amendment to the requirements of Table IWA-2210-1 can be extended to the examination of IWL items provided the indications for which the visual examination is performed can be detected at the chosen distance and illumination.
Relief is requested in accordance with 1 O CFR 50.55a(a)(3)(ii). Compliance with the specified requirements of this section would resu!t in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Alternative Examination(s)
VT-3 visual examinations will be performed under distance and illumination requirements necessary to detect the conditions or indications for which the visual examination is performed.
The procedure will be demonstrated capable of detecting conditions or indications for which the examination is being performed.
Staff Evaluation of RR-IWL-2 The staff agrees with the licensee that compliance with the requirements specified in the provisions of Table IWA-2210-1 for direct visual VT-3 examinations for concrete containment is
unnecessary and would result in hardship or unusual difficulty without a _compensating increase in the level of quality and safety. The requested relief is granted.
3.0 CONCLUSION
Based on the review of the information provided in RR-IWE-2, 4, 5, 6 and IWL-2, the staff concludes that the licensee's proposed alternative in each case provides an acceptable level of quality and safety. Therefore, pursuant to 1 O CFR 50.55a(a)(3)(ii), the proposed alternative of the licensee's relief requests is authorized for Surry, Units 1 and 2, during the third 10-year interval.
Principal Contribute;-: J. Ma Date:
April 14, 1999