ML18153C944
| ML18153C944 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 03/25/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18153C943 | List: |
| References | |
| NUDOCS 9203300026 | |
| Download: ML18153C944 (4) | |
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e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUIREMENTS REGARDING COMPONENT COOLING WATER HEAT EXCHANGERS VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 ANO 2 DOCKET NOS. 50-280 AND 50-281
1.0 INTRODUCTION
By letter dated July 23, 1987, as supplemented November 13, 1987, Virginia Electric and Power Company (VEPCO, the licensee) requested relief from certain ASME Boiler and Pressure Vessel Code (ASME Code)Section XI requirements with regard to the replacement of component cooling water heat exchangers (CCWHXs) and recirculation spray heat exchangers at the Surry Power Station, Units 1 and 2.
In a Safety Evaluation (SE) issued February 25, 1988, NRC granted relief for utilizing replacement heat exchangers which did not meet the replacement requirements of ASME Code Section XI for "N" stamping per ASME Section III. Alternatively, the replacement heat exchangers would meet the requirements of ASME Section VIII and be procured from a vendor with an approved 10 CFR Part 50, Appendix 8, quality assurance program.
This evaluation was consistent with later guidance issued in Generic Letter 89-09, "ASME Section III Component Replacements," dated May 8, 1989.
During an interim period in 1987 while procuring the replacement heat exchangers discussed above, replacement of the CCWHX channel heads was necessitated due to severe material degradation identified during the dual unit outages in early 1987 as described in VEPCO's letter dated February 24, 1987.
These channel heads were procured from stock material from the manufacturer of the original heat exchanger assemblies.
These channel heads were manufactured to ASME Section XI requirements, but at the time of
, manufacturing and procurement, the manufacturer did not have an approved 10 CFR Part 50, Appendix 8, quality assurance program.
The NRC staff verbally approved the use of these channel heads on an interim basis.
2.0 RELIEF REQUEST Currently, all but one of the degraded CCWHXs that had the replacement channel heads have been replaced with the new heat exchangers in accordance with the NRC SE issued February 25, 1988.
For the remaining CCW heat exchanger, the licensee has requested NRC approval of relief from the replacement requirements of ASME Section XI to allow use of the heat exchanger as currently installed and serviceable until such time that the condition of the heat exchanger necessitates replacement.
9203300026 920325 PDR ADOCK 05000280 P
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e 2.1 Proposed Alternative The "A" and "B" CCWHXs in Surry Unit 1 were replaced during the 1989 refueling outage.
The "D" CCWHX in Surry Unit 2 was replaced in a non-outage period during the winter of 1988-1989.
The Surry Unit 2 "C" CCWHX has not been replaced, and is the original heat exchanger with replacement channel heads.
The licensee proposes to continue to monitor the condition of the "C" CCWHX as currently installed and not replace it until such time that degradation necessitates replacement.
If any channel head degradation is identified that requires a Code repair or prevents the heat exchanger from meeting Section XI operability requirements, the "C" heat exchanger channel heads will be repaired during the operating cycle and the entire heat exchanger replaced at the next outage of sufficient duration. Additionally, by letter dated February 10, 1992, the licensee committed to and subsequently performed the following material verification testing on the "C" CCWHX channel heads.
o Alloy Verification - A Spectrotest F chemical analysis was performed on the channel head shells to verify that the material composition is within the acceptance criteria provided in ASTM A516.
o Hardness - An impact-type hardness test using Rockwell "B" standards was performed to verify that the material hardness is within allowable limits as specified in ASTM A516.
o Thickness - Ultrasonic testing of the CCWHX channel heads was performed at several locations to verify that the actual wall thickness is greater than the minimum design wall thickness.
Each of these tests was performed in place with portable equipment and the results compared to the manufacturer's specifications.
2.2 Licensee's Basis for Relief The replacement CCWHX channel heads were designed and fabricated per ASME Section VIII, but were not manufactured under an Appendix B quality assurance program.
The licensee states that they have reasonable assurance as to the adequacy of the channel heads for the following reasons:
(1) the interim channel heads were purchased from the original CCWHX manufacturer; (2) although initially not qualified as an Appendix B program, the manufacturer's quality assurance has been upgraded to Appendix B for the subsequent procurement of replacement CCWHXs; and (3) design, fabrication, inspection and quality assura*nce requirements of ASME Section VII I meet or exceed the ASME requirements specified for the original channel heads (licensee's letter of September 23, 1988}.
By letter dated April 6, 1987, the licensee provided the results of a Code reconciliation between the original component requirements of ASME Section III, 1968 Edition, Subsection C (which references the user to ASME Section VIII, 1968 Edition, but required the component to be "N" stamped by the
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- supplier}, and the replacement channel head requirements of ASME Section VIII, 1986 Edition. This reconciliation determined that the design, fabrication, inspection, and testing requirements of the replacement channel heads meet or exceed the requirements of the original components.
VEPCO's letter of December 6, 1991, provided further information, stating that because the replacement channel heads were manufactured to ASME Section VIII, the process included adequate controls for design, manufacturing, testing, and material. Nondestructive examinations (radiography and liquid penetrant} were performed on the channel heads.
During installation in April 1987, the channel heads successfully passed system hydrostatic and inservice leak tests.
The form and fit requirements for the channel heads were demonstrated by the initial fit-up and assembly.
Subsequent fit-ups and reassemblies during maintenance have further verified the form and fit.
3.0 EVALUATION ASME Section XI, Subsection IWA-7000, provides the requirements for replacement of inservice components.
Specifically, replacements should meet the applicable construction code to which the original item was constructed, and the existing design requirements. Alternatively, the replacement may meet all or portions of the requirements of later editions of the construction code or Section III, when the construction code was not Section III, provided (1) the requirements affecting the design, fabrication, and examination of the item to be used for replacement are reconciled with VEPCO's original design requirements through the stress analysis report, design report, or other suitable method that demonstrates the item is satisfactory for the specified design and operating conditions, (2) mechanical interfaces, fits, and tolerances that provide satisfactory performance are compatible with system and component requirements, and (3) materials are compatible with installation and system requirements.
The original construction code (ASME Section III, Class C components) required that Class C vessels be "N"-stamped below the "U"-stamp of Section VIII.
The manufacturer no longer maintains an "N"-stamp.
NRC Generic Letter 89-09 recognized that many manufacturers are dropping their "N"-stamp programs due to the decline in nuclear plant orders in the United States and the limited demand of ASME Section III components.
The generic letter indicates that where replacements are no longer available in full compliance with the stamping and documentation requirements of Section III of the Code, they should be procured under the utility's Quality Assurance (QA) Program that is in conformance with 10 CFR Part 50, Appendix B, and meet all other applicable requirements of Section III endorsed by NRC regulations except that the Code "N"-symbol need not be applied.
An example of evidence that the quality of the replacement is adequate, which is given in the generic letter, discusses the replacement of an ASME Section Ill, Class 3 nuclear-stamped heat exchanger with an ASME Section VIII stamped heat exchanger.
Generic Letter 89-09 was issued after the licensee had installed the replacement channel heads, but the actions taken at the time of installation were consistent with the later guidance in the generic letter. Additionally, the licensee performed a Code reconciliation between the original construction
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e Code requirements and the code of construction of the replacement channel heads.
The form, fit, and function were verified.
However, the licensee provided no information on the receipt and inspection of the channel heads to verify the material certifications supplied by the manufacturer.
Because the manufacturer/supplier did not have an approved Appendix B QA program at the time of procurement, the replacement channel heads were procured as commercial-grade components.
Therefore, it is the licensee's responsibility per 10 CFR Part 21 to "dedicate" the channel head.
"Dedication" of a commercial-grade item occurs after receipt when that item is designated for use as a basic component.
If the channel heads are adequately dedicated for use, they can provide an acceptable level of quality and safety. Requiring the licensee to replace the remaining channel heads would necessitate replacement of the entire heat exchanger, which could require shutdown of the plant to facilitate system conditions required to complete the replacement activity. This would constitute a hardship without a compensating increase in the level of quality and safety.
Relief from the requirements of ASME Section XI was contingent on the licensee completing the dedication of the item per 10 CFR Part 21 by verifying that the material of the channel heads conforms to the material certifications provided by the manufacturer/supplier. This includes actual physical verification through demonstration such as material analy"sis, hardness tests, and thickness measurements.
Satisfactory material verification testing was completed by the licensee on February 20, 1992, as confirmed by a telecon on March 5, 1992.
Records of. the tests are to be maintained with the component documentation.
The licensee's dedication of this item will be subject to NRC inspection.
- 4. 0 CONCLUSION Relief is granted from the replacement requirements of ASME Section XI, Subsection IWA-7000, for the "C" CCWHX channel heads, pursuant to 10 CFR 50.55a(a)(3)(i) and (a)(3)(ii), on the basis that (1) the replacement item provides an acceptable level of quality and safety; (2) requiring replacement of the entire heat exchanger, which currently has no evidence of degradation, would create a hardship and burden on the licensee without a compensating
- increase in the level of quality and safety; and (3) the licensee's proposed monitoring of the condition of the channel heads until such time as they are replaced provides an additional measure of assurance of the operability of the components; provided the licensee has documented an adequate dedication of the item in accordance with 10 CFR Part 21.
Date: March 25, t992 Principal Contributor:
Patricia Campbell