ML14183A640
| ML14183A640 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 03/01/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML14183A639 | List: |
| References | |
| NUDOCS 9503060312 | |
| Download: ML14183A640 (6) | |
Text
,pj REG 0 f' UNITED STATES 9-NUCLEAR REGULATORY COMMISSION CO
&WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF CAROLINA POWER & LIGHT COMPANY H.B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261
1.0 INTRODUCTION
The Technical Specifications for H.B. Robinson, Unit No. 2 (HBR), state that the inservice inspection and testing of the American Society of Mechanical 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 (ASME 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). Title 10 of the Code of Federal Regulations, Part 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 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 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 10-year 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 10 CFR 50.55a(b) on the date 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the H.B. Robinson, Unit 2 (HBR), third 10-year inservice inspection (ISI) interval is the 1986 Edition. 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 and subject to Commission approval.
Pursuant to 10 CFR 50.55a(g)(5)(iii), 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 9503060312 950301 PDR ADOCK 05000261 PDR
-2 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, 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.
By letter dated July 29, 1994, Carolina Power & Light Company (licensee) requested relief from the ASME Code,Section XI, scheduling requirements for reactor pressure vessel examination categories B-A, B-D, B-F, B-G-1, and B-N-i at HBR. In a letter dated January 3, 1995, the licensee withdrew examination category B-G-1 from its request for relief and provided additional information regarding the other examination categories. The NRC has reviewed the licensee's request along with the supporting information and the evaluation is presented in the following sections.
2.0 BACKGROUND
Request For Relief From The ASME Code Scheduling Requirements Of Reactor Pressure Vessel Examination Categories B-A, B-D. B-F, and B-N-1 Component Identification Examination Category/Item ID Number B-A/B1.30 Shell-to-Flange Weld #3 B-D/B3.90 Hot-Leg Nozzle-to-Vessel Welds 29, 31, & 33 B-D/B3.100 Hot-Leg Nozzle Inside Radii 29, 31, & 33 B-F/B5.10; B5.130 Hot Leg Nozzle-to-Safe End Weld #1 DM Safe End-to-Pipe Weld #1 on Each Loop (6 welds)
B-N-1/B13.10 Vessel interior ASME Code Section XI Third Interval Requirements The 1986 Edition of the ASME Code, Table IWB-2500-1, Examination Category B-A, Item B1.30, requires a 100 percent volumetric examination of the reactor pressure vessel (RPV) shell-to-flange weld as defined by Figure IWB-2500-4.
Fifty percent of the examination shall be completed by the end of the first inspection period and the remainder by the end of the third inspection period.
Partial deferral is allowed if an examination is conducted from the flange face; the remaining volumetric examinations from the vessel wall may be performed at or near the end of the interval.
Examination Category B-D, Items 83.90 and B3.100, requires a 100 percent volumetric examination of the RPV nozzle-to-vessel and nozzle inside radius sections as defined by Figure IWB-2500-7. At least 25 percent, but not more than 50 percent (credited) of the nozzles shall be examined by the end of the first inspection period, and the remainder by the end of the inspection interval.
-3 Examination Category B-F, Items B5.10 and B5.130, requires a 100 percent volumetric examination of the RPV nozzle-to-safe end welds, and safe-end-to pipe welds that are nominal pipe size 4 inch or larger as defined by Figure IWB-2500-8. These examinations may be performed coincident with vessel nozzle examinations required by Category B-D.
Examination Category B-N-1, Item B13.10, requires visual examination VT-3 of the RPV interior (accessible areas) each inspection period, deferral to the end of the interval is not permitted.
Relief Requested Relief is requested from the ASME Code scheduling requirements for reactor pressure vessel examination categories B-A, Item B1.30; B-D, Items B3.90 and B3.100; B-F, Items B5.10 and B5.130; and B-N-1, Item B13.10.
Proposed Alternative Examination The licensee proposed the following alternative in the July 29, 1994, letter to the NRC:
the required third 10 year interval, first period examinations will be combined with the requirements of the last period of the third 10 year interval exams. Additionally, the ten year exams will be accelerated forward so that all examinations will be performed on or before October 27, 2000. Thus no exams will exceed a 10 year span between examinations. Given the code allowed extensions for a ten year interval, these same examinations under "normal" scheduling could be performed as late as February 2003.
Licensee's Basis for Request The licensee stated that Relief is requested from the Code scheduling requirements. The third interval for H.B. Robinson Steam Electric Plant, Unit No. 2, began February 19, 1992, and concludes February 19, 2002. As part of the Ist
& 2nd ISI intervals, examinations were conducted on the RPV using the automated vessel tool as follows:
Code exams were performed at the end of the first 10 year interval along with the additional guidance of Regulatory Guide 1.150, Revision 0 in 1982.
Code exams were performed at the end of the first 40 month period of the second ten year interval in 1984 along with the additional guidance Regulatory Guide 1.150, Revision 1.
-4 At the end of the second 10 year interval all category B-A welds (with the exception of the three non-beltline region longitudinal welds in the upper shell) were examined along with 100% volumetric examination of the six nozzles to shell and their associated nozzle to safe-end and safe-end to pipe weld configurations. Additionally, the threaded stud holes and the reactor vessel interior and internals were examined as required. The additional guidance of Regulatory Guide 1.150, Revision 1, were also implemented. These exams were completed on October 27, 1990.
In addition to the Code required exams, 100% of all category B-A, Item B1.10, welds are scheduled for the end of the third ten year interval as required by the new rules.
Additional information regarding the examination categories was provided by the licensee in its letter dated January 3, 1995 as follows:
EXAMINATION CATEGORY B-A Although access is provided for manually scanning the flange surface with the reactor vessel closure head in place for the required 50% of the weld length..., clean up of the typically heavy build up of crud on the flange surface to achieve a suitable scanning surface creates an appreciable amount of contaminated waste in the form of scale and dust.
Additionally, the dose rates incurred during the cleaning and scanning operations at the flange are in the range of 150 mr/hr to 200 mr/hr.
Based on the personnel exposures expected for these examinations and cleanup and the fact that these are, at best, partial examinations, performance of these examinations within the 40 month period is of low value and accordingly should be deferred to the end of the current 10 year interval.
At that time, 100% coverage for 100 percent of the weld length will be achieved with the internals removed and scanning will be performed remotely with the reactor vessel tool from the vessel wall.
EXAMINATION CATEGORY B-D WELDS 29, 31, AND 33 (OUTLET NOZZLE TO SHELL WELDS)
EXAMINATION CATEGORY B-D NOZZLE INNER radii 29, 31, AND 33 (OUTLET NOZZLES)
EXAMINATION CATEGORY B-F NOZZLE TO SAFE-END AND SAFE-END TO PIPE WELDS (OUTLET NOZZLES)
Extensive examinations of the above listed areas have been previously performed as described below. Welds 29, 31, and 33, and associated Nozzle Inner Radii of welds 29, 31, and 33 were examined from the Nozzle Bores and the Vessel Wall at the end of the first and second ten year intervals (i.e., 1982 and 1990); additionally, the required 40 month examinations were performed on the same welds from the nozzle bores with internals installed in 1984.
-5 The Examination Category B-F Outlet Nozzle to Safe-End and Safe-End to Pipe welds were examined at the same time as the above listed Nozzle to Shell and Inner Radii.
Note that Carolina Power & Light Company has performed these exams on all six nozzles and safe-ends at the end of each ten year interval from both the nozzle bores and from the vessel wall as applicable.
.ASME Code Case N-521, "Alternative Rules for Deferral of Inspections of Nozzle-to-Vessel Welds, Inside Radius Sections, and Nozzle-to-Safe End Welds of a Pressurized Water Reactor (PWR) Vessel," approved by the ASME August 9, 1993, allows deferral of category B-D and B-F examinations under certain conditions, although this Code Case is not yet included in Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability ASME Section XI, Division 1, Revision 11."
The HBR meets the conditions specified in Code Case N-521.
As stated in the July 29, 1994, relief request, we [licensee] propose to accelerate the 10 year examinations forward in the interval such that examinations are scheduled not to exceed 10 years between examinations (i.e., on or before October 27, 2000).
This date is chosen based on the completion date of the 1990 examinations.... (not included in SE).
Based on the extensive previous examinations, performance of examinations on the outlet nozzles and safe-ends again during refueling outage 16 in April 1995, imposes unnecessary impacts in terms of cost, manpower, radiation exposures, and resources without a compensating increase in the level of quality and safety.
EXAMINATION CATEGORY B-N-1 VESSEL INTERIOR This relief was requested due to the extremely limited examinations that can be performed on the vessel interior with the lower internals installed, that is, the reactor vessel flange surface and nozzle inner surfaces as access permits. The risk of dropping or losing parts or equipment in the vessel or potentially damaging the internals with the equipment used for this exam outweigh the benefit if the examination is performed.
Based on the proposed alternatives as stated above, deferring the first 40 month period reactor vessel examinations to the end of the third ten year interval does not decrease the effectiveness of the reactor vessel examination schedule. Additionally, if the above Examination Category items were completed as currently required, the increase in the level of quality and safety achieved would be small in comparison to the burden of cost, manpower, radiation exposures, and resources required to perform the examinations.
-6 3.0 EVALUATION Paragraph IWB-2420(a), Successive Inspection, states that "the sequence of component examination established in the first inspection interval shall be repeated during each successive inspection interval, to the extent practical."
The licensee's last examination of the Category B-A, B-D, and B-F welds and nozzle inner radii that are the subject of this relief request was in October 1990. Relative to this relief request, the licensee stated that no exams will exceed a 10-year span between examinations.
Deferring specific examinations performed with automated inspection tooling until the end of the third interval is considered acceptable, provided that the time period between examinations of specific welds or components does not exceed 10 years. The licensee has committed to this provision.
Category B-A, B-D, and B-F weld examinations in this relief request use automated ultrasonic inspection tooling. Since the examinations performed with automated inspection tooling in the first and second periods of the second 10-year interval were performed again in the third period of the second interval, an acceptable level of quality and safety is achieved by performing these examinations in the third period of the third 10-year interval.
Examinations in the fourth 10-year ISI intervals must be completed within 10 years of the preceding examinations, or earlier.
The NRC finds that the ASME Code required examinations under Category B-N-1, Item B.13.10, can be performed by the licensee. However, considering the hardship incurred from this examination, the NRC has concluded that following the ASME Code required examination schedule does not provide a compensating increase in the level of quality and safety. The licensee's alternative provides an adequate level of quality and safety as long as the licensee performs a VT-3 visual examination of the accessible areas of the reactor vessel interior each time the lower internals are removed for plant inspection, maintenance, or repair activities.
4.0 CONCLUSION
The NRC has concluded that the licensee's proposed examination schedule for examination category B-A, B-D, and B-F welds provides an acceptable level of quality and safety. Therefore, pursuant to 10CFR 50.55a(a)(3)(i) the proposed alternative examination schedule for the Category B-A, B-D, and B-F welds is authorized, as requested, provided that the period of time between individual RPV weld or component examinations does not exceed 10 years.
The licensee has demonstrated that compliance with the specified requirements would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, the NRC has concluded that the part of the licensee's request for relief regarding the reactor vessel interior B-N-1, Item B13.10, is authorized, pursuant to 10 CFR 10.55a(a)(3)(ii), provided the licensee performs the VT-3 visual examination of the accessible areas of the reactor vessel interior each time the lower internals are removed for plant inspection, maintenance, or repair activities.
Principal Contributor: T. McLellan Date: March 1, 1995