ML20205Q556
| ML20205Q556 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 04/19/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205Q549 | List: |
| References | |
| NUDOCS 9904210304 | |
| Download: ML20205Q556 (3) | |
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j NUCLEAR REGULATORY COMMISSION wAswiworow, o.c. sees aos SAFET ' EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULAHON RELIEF REQUEST FROM CERTAIN ASME SECTION XI REQUIREMENTS L
I FOR CONTAINMENT INSPECTION UNION ELECTRIC COMPANY CALLAWAY PLANT. UNIT 1 DOCKET NO. 50-483 l
1.0 INTRODUCTION
By letter dated December 15,1998, Union Electric Company (UE or th6 licensee) submitted a request for relief from certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, Subsection IWL, for Callaway Plant, Unit 1.
Pursuant to 10 CFR 50.55a(b) and (g), inservice inspection c' :ontainment is required to meet the requirements of the 1992 Edition,1992 Addenda of Section XI, Subsections IWE and IWL.
Pursuant to 10 CFR 50.55a(g)(6)(ii)(B), the first period containment examinations must be completed by September 9,2001. Attematives to the iequirements of 10 CFR 50.55a(g) may l
be authorized under 10 CFR 50.55a(a)(3), if (i) the proposed attemative provides an acceptable level of quality and safety, or (ii) compliance witn the snecific requirement of the Code would result in hardship or unusual difficulty wit 1out a comp isating increase in the level of quality l
and safety.
l 2.0 DMCUSSION Code Reauirement and Relief Reauest The concrete portion of the Calisway Plant, Unit 1 containment building is subject to the rules I
and requirements for inservice inspection of Class CC (concrete containment) components, as applicable to IWL-2310, " Visual Examination and Personnel Qualification," and IWA-2210,
" Visual Examinations," of the ASME Boiler and Pressure Vessel (B&PV) Code,Section XI,1992 Edition, and 1992 Addenda. The Code requires spacific minimum illumination and maximum direct examination distance for all concrete surfaces. The licensee's relief request applies to the visualinspection of the exterior portion of the Callaway Plant, Un:11 containment building concrete surface.
9904210304 990419 PDR ADOCK 05000483 G
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.. Basis for Relief Section 50.55a of Title 10 of the Code of Federal Regulations was amended in the Federal Register (61 FR 41303) to require the use of the ASME B&PV Code,Section XI,1992 Edition, 1992 Addenda, when performing containment examinations. In addition to the requirements of Subsection lWL, the requirements of ASME B&PV Code,Section XI,1992 Edition,.1992 Addenda, Subsection IWA also apply for minimum illumination and maximum direct examination distance of Class CC (concrete containment) components, specifically for the examination of concrete under Paragraph IWL-2510. In accordance with IWA-2210, when remotely performing tha visual examinations required by Subsection lWL, Paragraph IWL-2510, using remote techniqum, the maximum direct examination distance specified in Table IWA-2210 may be exte ided, and the minimum illumiriation requirements specified in Table IWA 2210-1 may be decreased. The changs in examination and illumination requirements are allowed provided the remote examination procedure is demonstrated to resolve the required test chart characters in Table IWA-2210-1. In lieu of using the Table IWA 2210-1 test chart characters, the responsible engineer will use a combination of character and workmanship-based samples to determine the resolution required to ensure that indications of
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interest are detectable. The n 3ponsible engineer will also identify the minimum size fur
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indications of interest. For remote visual examination, the procedure and equipment to be used will be demonstrated capable of resolving these minimum indications to the satisfaction of the responsible engineer. The record of demonstration will be available to regulatory authoities.
In order to conform with Section XI, lWA-2000 requirements for visual examination, Subsection lWL referenced W-1 and VT-3 examinations, but designated them VT-1C and W-3C to signify that these were examinations of a concrete structure. The original VT-1 and VT-3 examinations in Subsection IWA were derdaned for use on metal surfaces. Flaw detection on metal surfaces requires the ability to rescw a much smaller indication than that required on concrete due to the small grain size of a metal surface in comparison to the much larger grain size of a concrete surface. The visual examination requirements for illumination levels and examination distances are too restrictive to demonstrate that the remote visual examination is equivalent to direct visual examination when performing examinations of concrete surfaces. The visual examination of a concrete containment is inter ded to uncover indications of significant conditions over a large area in a generally benign environment.
in editions of the ASME Code after 1992, the requirements for a VT-1C examination have been replaced with a " detailed visual examination," cnd the requirements for a VT-3C examination have been replaced with a " general visual examination." The general visual examination of a concrete surface is performed under the direction of the responsible professional engineer (RPE) to indicate the general structural condition of the containment. lWL-2000 references ACI-201.1 R-68 for guidelines used to determine concrete deterioration and distress. If the general visual examination detects any deterioration, the detailed visual examination is performed, again under the direction of the RPE, to determine the magnitude and extent of the i
deterioration. Ai'so, attemative lighting and resolution requirements have been added to later editions of Subsection IWL to be used in lieu of the requirements of IWA-2000. The licensee proposes to follow the requirements of this later version of the code for this relief request, beginning with the next concrete inspections, currently scheduled for May 1999.
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Q l Relief is requested in accordance with10 CFR Section 50.55a(a)(3)(i). Inspecting the concrete surfaces using increased distances and decreased illumination requirements, approved by the responsible engineer, will still allow the detection of flaws of a size sufficient to present a structural problem with the concrete structure.
Altemative Examination The licensee has proposed the following attemative:
Perform the concrete surface inspection remotely as required by Subsection lWL, Paragraph IWL-2510, extending the maximum direct examination distance, and reducing the minimum illumination requirements specified in Table IWA-2210-1.
3.0 gyALUATION The licensee has provided an attemative to the ASME Code requirements for the measurement ofillumination and examination distance for visual examinations. The visual examinations on concrete are performed to determine if damage or degradation, including cracks, wear, corrosion, erosion, or other physical damage, warrant additional evaluation or repair of the structure. In order for the visual examinations to be performed in such a way as to detect critical flaws, proper lighting is essential. The licensee has provided an attemative to Code requirements that uses a combination of character size and workmanship based samples to determine the resolution required to ensure that indications that might challenge containment integrity are detectable. Paragraph IWL-3111, Acceptance by Examination, requires that the responsible engineer determine what surfece conditions are acceptable and ensure there is no evidence of damage or degradation sufficient to warrant further evaluation or repair. Therefore, the licensee's responsible engineer will identify the minimum flaw size (indications of interest) required to be detected. For remote visual examinations, procedures and equipment used will be demonstrated to be capable of detecting and resolving these indications. The licensee will maintain a record of the demonstration perfomied.
While the use of the licensee's proposed attemative does not result in a quantitative evaluation of the illumination, it provides a method to verify that the indications of interest are visually detectable. The staff believes that the samples representing these n:dications should provide an appropriate simulation and concludes that visual verification, via direct or remote means, provides sufficient evidence of adequate illumination and examination distance.
4.0 CONCLUSION
Based on the evaluation of the information provided, the staff concludes that the proposed attemative provides an acceptable level of quality and safety. Therefore, the staff authorizes the use of the proposed alternative pursuant to 10 CFR 50.55a(a)(3)(i).
Principal Contributor: John Ma Date:
April 19,1999