ML20058C749
| ML20058C749 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 11/18/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058C747 | List: |
| References | |
| NUDOCS 9312020562 | |
| Download: ML20058C749 (5) | |
Text
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l WASHINGTOtv, D.C. 20555-0001 ENCLOSUREl SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 0F THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION RE0 VEST FOR RELIEF OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION DOCKJT NO. 50-285 P
1.0 INTRODUCTION
The Technical Specifications for Fort Calhoun Station 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 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)(1).
Paragraph 50.55a(a)(3) of Title 10 CFR of the Code of Federal Regulations 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 Boiler and Pressure Vessel Code (the 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 second 10-year interval comply with the requirements in the latest edition and addenda of Stction 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 Fort Calhoun Station Second 10-Year Inservice Inspection (ISI) Interval is the 1980 Edition, through Winter 1980 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.
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 9312O20562 931118 PDR ADOCK 05000285 0
PDR i
. Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(1), 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.
The licensee, Omaha Public Power District, submitted an alternative concerning volumetric examinations of regenerative heat exchanger (RHX) nozzle welds, in a letter dated October 16, 1992, for the second 10-year ISI interval which began September 26, 1983. The staff, with technical assistance from its contractor, the Idaho National Engineering Laboratory (INEL), has evaluated the subject alternative in the following sections.
2.0 EVALUATION AND CONCLUSIONS The staff, with technical assistance from INEL, has evaluated the information provided by the licensee in support of its proposed alternative to the ASME Boiler and Pressure Vessel Code (the Code),Section XI concerning the RHX nozzle weld inspections for the Fort Calhoun Station ISI program.
The staff has reviewed the attached INEL Technical Evaluation Summary and concurs in the contractor's evaluation and conclusions. Accordingly, pursuant to 10 CFR 50.55a(3)(ii), the licensee's proposed alternative is authorized on a one-time basis only, with the conditions that the licensee perform a volumetric examination of these nozzle-to-vessel welds (ISI #10 and #11) during the first refueling outage of the third 10-year inspection interval and that the licensee perform all additional RHX nozzle weld examinations on a schedule consistent with ASME Section XI. The volumetric examinations of two RHX nozzles and the surface examinations of the remaining nozzles, performed by the licensee during the current 10-year inspection interval, provide reasonable assurance of the continued structural integrity of the components.
Due to as low as reasonably achievable (ALARA) and scheduling constraints, compliance with Code requirements for volumetric examination of the remaining nozzles during the current 10-year interval would present an unusual hardship without a compensating increase in the level of quality or safety.
In addition, for third 10-year interval the staff will consider granting the licensee's request for relief (if submitted by the licensee) from Code requirement to volumetrically examine the nozzle inner radius sections.
Principal Contributor:
T. McLellan Date:
November 18, 1993
~
ENCLOSURE 2 TECHNICAL EVALUATION
SUMMARY
OF THE i
SECOND TEN-YEAR INTERVAL INSERVICE INSPECTION RE0 VEST FOR RELIEF FOR.
OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION DOCKET NO. 50-285
1.0 INTRODUCTION
The licensee, Omaha Public Power District, submitted a relief request concerning volumetric examinations of regenerative heat exchanger nozzle i
welds, in a letter dated October 16, 1992, for the second 10-year ISI interval which began September 26, 1983.
The Idaho National Engineering Laboratory (INEL) has evaluated the subject request for relief in the following sections.
2.0 EVALUATION The information provided by the licensee in support of the alternative to the t
Code requirements has been evaluated and the bases for authorizing the alternative is documented below.
s A.
Recuest for Relief. Examination Cateaory B-D. Items B3.150 and B3.160.
Full Penetration Welds of Nozzles in Vessels Code Recuirement: Table IWB-2500-1, Examination Category B-D, Items i
B3.150 and B3.160 require a volumetric examination of all primary side heat exchanger nozzle-to-vessel welds and nozzle inside radius sections, respectively.
Licensee's Code Relief Recuest: The licensee has requested relief from performing the Code-required volumetric examinations of primary side nozzle-to-vessel welds and inner radius sections for the regenerative t
heat exchanger (RHX) at Fort Calhoun Station.
Licensee's Basis for Recuestino Relief: The licensee stated:
"The RHX vessel at Fort Calhoun Station is a capped 10" diameter schedule 140 pipe. The geometric configuration of the 2-1/2" and 3" nozzles attached to the RHX results in an ultrasonic examination being extremely labor intensive while yielding minimal useful data. Additionally, the i
examination requires an extended time in a high radiation dose area.
Radiation levels of 1 - 2 REM per hour preclude the use of radiography as a volumetric examination technique. Thus, substantial personnel radiation exposure and an inability to use effective examination i
techniques make it impractical to perform volumetric examinations on the RHX nozzle welds or weld areas."
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...7 4
Licensee's Proposed Alternative: The licensee proposed to perform liquid penetrant examinations on the outer surface of the welds in lieu of the required volumetric examinations.
Evaluation: During discussion with the licensee, it was determined that RHX nozzle-to-vessel welds and inner radius sections had been previously l
examined during both the preservice inspection and the first 10-year inservice inspection interval.
It was also revealed that two of the four nozzles had been volumetrically examined during an earlier period of the current (second) 10-year interval. No recordable defect indications have been observed during the past volumetric examinations.
The licensee performed a liquid penetrant examination of the remaining two nozzle welds (ISI #10 and #11) during a recent refueling outage and observed no relevant indications.
After reviewing fabrication drawings with cross-sectional views of the nozzle welds and their inner radius sections, and considering the relative radiation exposure issues, we have determined that volumetric examinations of the nozzle inner radius sections provide limited degradation i.iformation due to the complex geometrical and metallurgical structure of the nozzles. However, the nozzle-to-vessel weld volumetric examinations can potentially provide meaningful evidence of the continued integrity of the welds. Additionally, personnel radiation exposures for volumetric examination of the nozzle-to-vessel welds would not be significantly higher than those required to perform liquid penetrant examinations on the outer surface of the welds.
Fort Calhoun Station reached the end of the current (second) 10-year inspection interval during the staff evaluation of this relief request.
Through discussions with the licensee, it has been determined that a substantial burden would be incurred by the licensee if required to examine the remaining two nozzle welds prior to the next refueling outage, i.e., the first refueling outage of the third 10-year inspection interval.
3 For this reason, the licensee's proposed alternative should be authorized on a one-time basis only, with the condition that the licensee perform a volumetric examination of these nozzle-to-vessel welds (ISI #10 and #11) during the first refueling outage of the third 10-year inspection l
interval, and that the licensee perform all additional RHX nozzle weld examinations on a schedule consistent with ASME Section XI.
3.0 CONCLUSION
Paragraph 10 CFR 50.55a(g)(4) requires that components (including supports) i that are classified as ASME Code Class 1, 2, and 3 meet the requirements, J
except design and access provisions and preservice requirements, set forth in j
applicable editions of ASME Section XI to the extent practical within the limitations of design, geometry, and materials of construction of the components.
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9 Pursuant to 10 CFR 50.55a(3)(ii), the proposed alternative should be authorized provided that the licensee performs the Code-required volumetric r
examination of the regenerative heat exchanger nozzle-to-vessel welds during the next refueling outage. The volumetric examinations of two RHX nozzles and the surface examinations of the remaining nozzles, performed by the licensee during the current 10-year inspection interval, provide reasonable assurance of the continued structural integrity of the components. Due to ALARA and scheduling constraints, compliance with Code requirements for volumetric examination of the remaining nozzles during the current 10-year interval would present an unusual hardship without a compensating increase in the level of l
quality or safety.
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