ML14191A416
| ML14191A416 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 09/18/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML14191A415 | List: |
| References | |
| NUDOCS 8909280164 | |
| Download: ML14191A416 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM REGULATORY REQUIREMENTS CAROLINA POWER & LIGHT COMPANY H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261
1.0 INTRODUCTION
The Technical Specifications for the H. B. Robinson Steam Electric Plant, Unit No. 2, state that the inservice inspection of ASME Code Class 1, 2, and 3 components shall be performed in compliance 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 10 CFR 50.55a(g)(6)(i) or an alternative authorized pursuant to 50.55a(a)(3).
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 his facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code require ment. After evaluation of the determination, pursuant to 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 and 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. Also, the use of alternatives to Code requirements may be authorized pursuant to 10 CFR 50.55a(a)(3) when (i) the proposed alternative would provide an acceptable level of quality and safety or (ii) compliance would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
In a letter dated June 23, 1988, the Carolina Power & Light Company (the licensee) requested relief from certain examination requirements of Section XI, 1977 Edition, including Summer 1978 Addenda, of the ASME Code for the H. B. Robinson Steam Electric Plant, Unit No. 2. Relief Requests No. 15-18 and supporting informa tion was evaluated by the staff in this Safety Evaluation.
2.0 EVALUATION Relief Request No. 15 Component - Pump Casing Welds and Internal Surfaces of the Pump Casings Code Requirement -
Volumetric and surface examination of all welds in at least one pump in each group of pumps performing similar functions in the systems, e.g., recirculating coolant pumps. Includes 100% of weld length and visual examination VT-1, of the internal surface of the same pump selected for volumetric examination of welds.
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-2 Relief Requested - Relief is requested from volumetric examination of the welds and visual examination of the internal surfaces of the reactor coolant pump casing for the following reasons:
- 1. Visual and volumetric examinations were performed on Loop "B" Reactor Coolant pump during the Spring 1982 Refueling Outage. These examinations were performed to satisfy the requirements for the first 10-year examination interval.
The nondestructive examinations were performed using visual and radiographic techniques and revealed no reportable indications.
- 2. Radiation exposure for the 1982 Reactor Coolant Pump "B" work required 41 man-rem. This exposure far exceeds the normal expected exposure for an ISI outage program.
- 3. The reactor coolant pump casting at H. B. Robinson consists of four cast rings made from Type 316 stainless steel joined by three circum ferential vessel welds. The pump internals are removed and stored in the reactor vessel cavity during radiographic and visual examinations, then returned to the pump. These movements create the possibility for damage during disassembly or transport of the internals.
- 4. Carolina Power & Light Company states that the increased radiation exposure and excessive costs associated with performing these internal examinations far exceed the benefits that might be achieved by the examinations, particularly since the 1982 examination revealed no reportable indications, and the proposed alternative would satisfy any safety concerns.
Alternative Examination - The licensee proposed the following alternative examination:
Visual examination will be performed to determine whether unanticipated severe degradation of the pump casting is occurring due to phenomena such as erosion, corrosion, or cracking. However, previous experience during examination of pumps at this and other plants has not shown any significant degradation of pump castings. The concept of visual examination if the pump is disassembled for maintenance is acceptable. The disassembly of the pumps solely for the purpose of inspection is a major effort and, in addition to the possibility of additional wear or damage to the internal surfaces of the pumps, would result in large amounts of radiation exposure to personnel. However, if the pumps are disassembled for maintenance, the internal surfaces would be examined.
Conclusion - The staff finds that increased radiation exposure and costs associated with performing the internal examinations are not commensurate with the level of quality and safety provided by the Code examination. It is concluded that compliance with the specific requirements of Section XI would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety. Therefore, pursuant to 50.55a(3)(ii), the staff accepts the alternative examination proposed by the licensee to ensure that no unanti cipated severe degradation processes have occurred to challenge the structural integrity of the castings of the reactor coolant pumps.
-3 This relief is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest considering the burden that would result on CP&L if the Code requirements were imposed.
RELIEF REQUEST NO. 16 Component - Bolts and Studs Code Requirement - Article 5,Section V, Volumetric Examination of Bolts and Studs.
Relief Requested - Relief is requested from the Article 5 Section V calibration requirements.
Alternative Examination - As an alternative examination to the Article 5,Section V calibration requirement, calibration will be performed on each stud or bolt examined using back-surface response calibration.
Basis for Relief - The licensee stated that by using back-surface response calibration techniques, the question of material differences would be elimina ted as calibration would be performed on the bolts/studs being examined.
Where calibrations are performed on a test bar of the same nominal diameter and composition as required by Article 5 of Section V, material differences would be encountered over the range of studs/bolts in the assemble.
Evaluation - Insufficient information was submitted by the licensee to show that Article 5,Section V calibration requirements were impractical to perform at H.B. Robinson Steam Electric Plant, Unit No. 2.
Conclusion - The licensee did not show that the Article 5,Section V calibra tion requirement was impractical for the H.B. Robinson Steam Electric Plant, Unit 2. Therefore, relief request No. 16 is not granted.
RELIEF REQUEST NO. 17 Component - Nozzles in vessels over i-inch in nominal thickness Category C-B, Item C2.20.
Code Requirement - Surface and volumetric examinations of all nozzles at terminal ends of piping runs that conect to vessels.
Relief Requested -
Relief is requested from volumetric examination of the steam generator nozzle inner radius section of the 31-inch main steam and the 18-inch feedwater nozzles.
Alternative Examination - A visual examination of the inner radius section will be performed if access permits and only if the steam generators are open for other types of examiation or for maintenance.
-4 Basis for Requesting Relief - The licensee stated that with regard to the steam-generator, the 31-inch main steam nozzle and the 18-inch feedwater nozzle configurations of nozzle to vessel at the inner radius section prevent meaningful volumetric examination. The licensee stated that practical alternative techniques to volumetric examination of these areas are not presently available.
Evaluation - Insufficient information was presented by the licensee to show that Category C-B, Item C2.20 ASME Code requirement was impractical to perform at H.B. Robinson Steam Electric Plant, Unit 2.
Conclusion - The licensee did not show that volumetric examination of the steam generator nozzle inner radius section of the 31-inch main steam ant the 18-inch feedwater nozzle was impractical to perform at the H.B. Robinson Steam Electric Plant, Unit 2. There for, relief request No. 17 is not granted.
RELIEF REQUEST NO. 18 Component - Circumferential Shell Welds in Seal Water Filter Category C-A, Item C1.10.
Code Requirement - Volumetric examination of circuferential shell welds at gross structural discontinuities during each inspection interval on 100% of the length of the welds.
Relief Requested - The licensee requested relief from the volumetric examination of the seal water filter head to-shell weld, shell to flange weld, and head to flange weld.
Alternative Examination - A liquid penetrant examination was proposed as an alternative examination. The licensee proposed to perform a liquid penetrant examination of the welds and on i-inch of the base metal on each side of the welds for 100% of the weld length in lieu of the volumetric examination.
Basis for Requesting Relief - The thickness of the material used in the construction of this component (0.188-inch) is such that meaningful results could not be expected with ultrasonic examination as required by IWC-2500-1.
The licensee states that the proposed alternative examination is as capable of detecting significant defects in 0.188-inch material as the ASME Code required ultrasonic examination.
Evaluation - The staff agrees with the licensee's assessment that meaningful results may not be obtained through ultrasonic examination of material at gross structural discontinuities. However, insufficient information was presented by the licensee to show that the Category C-A code requirement was impractical to perform at the H.B. Robinson Steam Electric PLant, Unit 2.
Conclusion - The licensee did not show that the circumferential shell welds in the Seal Water Filter was impractical to perform at the H.B. Robinson Steam Electric Plant, Unit 2. Therefore, Relief request No. 18 is not granted.
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3.0 CONCLUSION
We conclude from our evaluation of the information submitted by the Carolina Power and Light Company that relief may be granted for request No. 15, "Pump Casing Welds and internal surfaces of the Pump Casing," and not granted for requests, No. 16, "Bolts and Studs-Calibration Standards," No. 17, "Nozzles in Vessels, and No. 18, "Circumferential Shell Welsd in Seal Water Felter."
The licensee failed to show why the latter requirements were impractical to perform at the H.B. Robinson Steam Electric Plant, Unit 2.
Principal Contributor:
F. Litton Dated:
September 18, 1989