ML18150A032
| ML18150A032 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/15/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18150A031 | List: |
| References | |
| TAC-59754, NUDOCS 8704170013 | |
| Download: ML18150A032 (5) | |
Text
..
_\\
8ackground SAFETY EVALUATION REPORT SURRY POWER STATJnN UNIT 2 DOCKET NUMRER 50-281 R[OUEST FOR RELIEF FROM ASME SECTION XI REQUIREMENTS ENCLOSURE By letter dated September 19, 1985, Virginia Electric and Power Company (the licensee) requested relief from certain inservice examination requirements of ASME Section XI (74S75) at Surry Power Station Unit 2. The licensee submitted additi'onal information to the NRC relative to the reouest in a letter dated September 30, 1986. The inservice examination requirements from which relief was requ~sted, the bases stated by the licensee for requestinq relief and t~e NP.C staff's evaluation and conclusions regarding the relief requested are described in the following paragraphs. The degree of relief which the staff has concluded may be granted pursuant to 10 CFR 50.55a(g)(6)(il, is applicable to the first ten-year inspection interval.
Relief Requested, Bases and Staff Evaluation, and Conclusions
- 1.
Inservice Examination of ASME Class 1 Regenerative Heat Exchanger 2-CH-E-3
- a.
- b.
Relief Requested In a letter dated February 28, 1984, the N~C staff responded to an earlier request from the licensee for relief from ASME Section XI reouirements for volumetric examination of nozzle to vessel welds in this heat exchanger, granting partial relief from the ASME requirements and specifying alternate volumetric and surface examination requirements.
The licensee now requests relief from these latter requirements and from ASME Section XI requirements for volumetric examinations of the head-to-shell and shell-to-tube sheet welds.
They propose that the hydrostatic test, already required by ASME Section XI, IWB-5000, suffices to demonstrate the continued acceptability of the regenerative heat exchanger welds.
Licensee's Rasis for Requesting Relief The examinations will result in significant personnel radiation exposures, estimated to be 15 man-rem, without a compensating increase in assurance of safe operation.
- c.
NRC Staff Evaluation and Conclusions Information provided by the licensee in their September 30, 1986, letter indicates that the regenerative heat exchanger can be readily isolated in the event of its leakage or failure without any significant reduction in the capability of the plant to be shut down.
Also, the heat exchanger is located within the containment, which affords additional confinement of any leakaae that might occur.
87041700i3 8704l~
.\\
.e
?
L.
Considering these factors, the staff agrees that the licensee's performance of the required volumetric and surface examinations would result in excessive personnel exposures without an adequate compensating increase in the level of safety. The staff considers, however, that complete omission of the volumetric and surface examinations is undesirable. The reqenerative heat exchanger is actually composed of three heat exchangers connected in series. Based on information provided in the licensee's September 30, 1986, letter, it is estimated that the head-to-shell, shell-to-tube sheet and nozzle-to-shell welds in the bottom (heat exchanger) component may be examined in accordance with the requirements stated in ASME Section XI and the previously granted relief with a personnel exposure estimated to be 2.34 man-rem~.
The staff does not consider this exposure excessive and has determined that the volumetric and surface examinations of the bottom heat exchanger component welds, together with the hydrostatic test already specified by ASME Section XI, should be performed to adequately assure the integrity of the regenerative heat exchanger.
The staff concludes that the relief requested by the licensee should be partially granted, such that the surface and volumetric examinations previously specified for the entire heat exchanger may now he limited to the bottom heat exchanger component.
- 2.
Inservice Examination of ASME Class 2 Seal Water Return Filter 2-CH-FL-3
- a.
- b.
Relief Requested In a letter dated February 28, 1984, the NRC staff responded to an earlier request from the licensee for relief from ASME Section XI (74S75) requirements for volumetric examination of head-to-shell, shell-to-flange and top head welds in the filter vessel. Relief was granted
- to substitute surface and visual examinations for the volumetric examinations. The licensee now reouests relief from these altered examination requirements and from ASME Section XI (74S75) requirements for surface examination of the vessel support welds.
They propose that the hydrostatic test, already required by ASME Section XI, IWB-5000, suffices to demonstrate continued acceptability of the filter vessel welds.
Licensee's Basis for Requesting Relief The examinations will result in significant personnel radiation exposures, estimated to be two to four man-rems, without a compensating increase in assurance of safe operation.
- c.
NRC Staff Evaluation and Conclusions Information provided by the licensee in their September 30, 1986, letter indicates that this filter can be readily isolated and bypassed in the event of leakage or failure without affecting the capability of the plant to be shut down.
The design operating temperature and pressure are moderately low (250°F and 200 psig) and there is no equipment essential for safe shutdown located in close proximity.
- Considering these factors, the staff agrees that the personnel exposures expected in performing the required surface examinations are not adequately compensated through an increased assurance of plant safety. The staff finds that the hydrostatic test already specified by ASME Section XI, which includes a visual examination for leakage, will adequately assure the integrity of the seal water return filter.
The staff concludes that the relief reQuested by the licensee for examination of the seal water return filter should *be granted.
- 3.
Inservice Examination of ASME Class 1 Residual Heat Removal Return Isolation Valve MOV-RH-2720B
- a.
Relief Requested The licensee has requested relief from the ASME Section XJ (74S75) requirement for visual inspection of the internal pressure boundary of the valve. They propose that the hydrostatic test, already required by ASME Section XI, IWB-5000, suffices to demonstrate the continued acceptability of the valve pressure boundary.
The licensee stated that they had previously been granted relief from visual inspection by substitution of alternate material thickness examinations from the exterior surface for the identical Unit 1 valve (January 24, 1984 NRC Evaluation Letter) and that they had unsuccessfully attempted such examinations on valve MOV-RH-27208.
- b.
Licensee's Basis for Requested Relief
- \\.
The requirements to disassemble this primary system valve for the sol~
purpose of performing a visual examination of the internal pressure boundary surfaces has only a very small potential of increasing plant safety margins and a very disproportionate impact on expenditures of plant manpower and radiation exposure.
Performing this internal visual examination, under such adverse conditions as high dose rates and poor surface condition, realistically, provides little additional information as to the valve casing integrity.
The performance of valve bodies has been excellent in PWR applications and continued excellent service performance is anticipated.
- c.
NRC Staff Evaluation and Conclusions The disassembly of valve MOV-RH-2720B to the degree necessary to visually examine its internal pressure retaining surfaces would result in the expenditure of relatively large effort and personnel radiation exposure as compared to the increase in assurance of pressure boundary integrity that would be provided.
In view of th,s, the staff has concluded that disassembly of the valve solely for the visual examination is impractical. Should the valve be disassembled for maintenance, however, little additional expenditure of effort or exposure should be necessary for performance of the examination, and under such conditions, the staff concludes that the examination must
I l.\\ be perfonned and properly documented.
The staff is satisfied that the performance of visual examinations when maintenance is required together with leakage tests and weld examinations* already required by ASME Section XI will provide adequate assurance of the pressure boundary integrity of valve MOV-RH-2720R.
The staff concludes that the relief requested by the licensee should be partially granted, with internal visual examination of valve MOV-RH-27208 required only if the valve is disassembled for maintenance, as described above.
- 4.
Compliance with the Original or Later Editions of the Construction Code for Replacements
- a.
Alternative Requested
- b.
The current code edition applicable to Surry, ASME Section XI {80W80) states in paragraph IWA-7210(a) that replacement components shall meet the original construction code requirements or, alternatively, the requirement of IWA-7210(c).
IWA-7210(c) states that replacements may meet the requirements of later editions of the construction code (in this case USAS B-31.1-1967), provided any additional requirements are met and that the later edition has been approved by the NRC.
No later editions of USAS 831.1 were approved by the NRC for nuclear work in 10 CFR 50.55a, therehy limiting Surry,*under the rules of ASME
- Section XI, to the original code in power piping/component type replacement.
The licensee requested that the use of ASME Section III be permitted in the same context that paragraph IWA-7~10{c) above is intended for later editions of the original construction code for these types of replacements.
Licensee's Bases for Requesting Alternative Use of ASME Section III, allows the use of more "state of the art" requirements and provides flexibility in perfonning replacements.
Some components may be more readily procured to ASME Section III requirements than to the original construction requirements.
- c.
NRC Staff Evaluation and Conclusions As indicated by 10 CFR 50.55a(a)(3)(i), proposed alternatives to the requirements of paragraph (g) of 10 CFR 50.55a may be used if it is demonstrated that they would provide an acceptable level of quality and safety.Section III of the ASME Code is endorsed by the NRC as referenced in 10 CFR 50.55a(b) for use in the design, fabrication, and testing of nuclear power plant components.
In addition to the design, fabrication, and testing requirements of Section III, the replacements are governed by the requirements of applicable paragraphs of article JWA-7000 of Section XI. These requirements will ensure that the replacements are verified for acceptability prior to installation, i.e., material compatibility, that mechanical interfaces, fits, and tolerances provide satisfactory perfonnance, and that the replacement meets the design and operating conditions. Consequently, the licensee's proposal is acceptable to the staff.
The staff has determined that the relief requested by the licensee may be granted, as described above, pursuant to 50.55a(g){6)(i). With respect to relief requests 1-3, the staff has determined that the requirements of the code are impractical and relief granted is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. With respect to request 4, the staff has determined that the alternative requested by the licensee is acceptable pursuant to 10 CFR 50.55a(a)(3)(i).
Principal Contributor:
E. Girard