ML20215D081
| ML20215D081 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/30/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20215D074 | List: |
| References | |
| NUDOCS 8610100636 | |
| Download: ML20215D081 (5) | |
Text
'
ENCLOSURE SAFETY EVALUATION REPORT ON REQUEST FOR RELIEF FROM INSERVICE HYDR 0 STATIC TEST RE0lJIREMENTS VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-338 & 50-339 BACKGROUND By letter dated June 13, 1986, Virginia Electric and Power Company (the licensee) requested relief from certain inservice hydrostatic pressure test requirements of the 1980 Edition of Section XI of the ASME Code at North Anna Power Station, Units 1 and 2.
This report provides an evaluation of the licensee's request, supporting information, and alternative examinations or tests, as well as the staff's bases for granting the request pursuant to 10 CFR 50.55a(g). The relief granted remains in effect for the first ten-year inspection interval unless revised or modified prior to the end of the interval. The relief request is evaluated below.
EVALUATION OF RELIEF REQUEST Class 3 Hydrostatic Pressure Test of Service Water Spray System The licensee is upgrading the Service Water System at North Anna Units 1 and P.
The scope of this project includes installation of a new Service Pater Reservoir spray and bypass piping system which will replace the existing fiberglass spray system currently in operation.
A complete description of the replacement system is outlined in Enclosure 1 to the licensee's submittal.
Repairs and replacements will meet the reouirements of ASME Section XI 1980 Edition through Winter 1981 Addenda, Subsections IWA, IWB, IWC and IWD 4000.
Where reference is made to other subsections of the Code, the subsection 8610100636 860930" DR ADOCK 0500 8
2-requirements of ASME Section XI 1974 Edition through Summer 1975 Addenda apply.
For determining the suitability of replacements, the requirements of Subsections IWA, IWB, IWC and IWD 7000 of the 1980 Code and subsequent Addenda are used for guidance.
Code Examination Reauirement Article IWA-7210 of Section XI (1980) states that replacements nust meet the requirements of the original construction code for the component or part being replaced. The original construction code for the Service Water System is ANSI (formerly USAS) B31.7-1969 Edition with Addenda through 1970. The Service Water System is governed by Class 3 requirements of that Code for design, materials, dimensions, fabrication, assembly, erection, inspection and testing.
For examination and testing of Class 3 nuclear piping, B31.7 refers to the reoufrements of ANSI B31.1-1967 Edition with additional nondestructive examination of welds as described in the 1970 Addenda of B31.7. As part of the examination and testing requirements, B31.1, Chapter VI, Paragraph 137, requires leak testing prior to initial operation. This leak testing may be accomplished through hydrostatic testing, pneumatic testing, initial service leak testing, vacuum testing or 100% radiography of all welded joints in an all welded system.
Code Relief Request t-Relief is requested from the hydrostatic test requirements of B31.1 for the spray and bypass piping system downstream of the spray and bypass isolation valves.
. Licensee Basis for Relief New piping and equipment (i.e., valves, expansion joints, fittings) being installed under the scope of this project, from the point of tie-in at the existing buried headers up to and including the new spray and bypass isolation valves in the new valve house, will be hydrostatically tested and/or inservice leak tested prior to initial operation.
(Enclosure 2 to the licensee's submittal provides a layout of the proposed hydrostatic testing boundaries).
For the spray and bypass piping downstream of the isolation valves out to the spray nozzles, hydrostatic testing will be difficult and impractical due to the system design. The spray piping is divided into eight arrays, each containing 104 two-inch horizontally threaded nozzle connections. Since each of these connections is located on nearly the same horizontal plane, it will be virtually impossible to ensure a fully vented, completely water filled system prior to hydrotest (i.e., with the nozzle connections temporarily capped).
It would be difficult to test the system with the nozzles in place because of the inability to effectively plug the smooth orifice outlet of the nozzle as well as the aforementioned venting problems.
The code (B31.1) allows an inservice leak test in lieu of a hydrostatic test when the hydrostatic test is not practicable.
In this case, it would also be difficult to demonstrate leak tightness of each welded joint by inservice leak testing due to the spraying action which would be present during array operation.
It should be noted that Section XI also requires inservice system pressure tests (i.e., hydrostatic tests) as part of the inservice inspection program.
North Anna Power Station Administrative Procedure ADM 10.5, Inservice Inspection Visual Examination Procedure VT-?, references the 1977 Edition including Addenda through Summer 1970 of Section XI for system pressure test
. requirements. The Code states that for open ended portions of nonclosed systems, the system pressure test is not required. Article IWD-5223(c) of the Winter 1977 Addenda reads:
"For open ended portions of nonclosed system, any test or observation during. system operation that demonstrates unimpared flow shall be acceptable in lieu of a system pressure test." Additional guidance is provided in later editions and addenda. Article IWD-5223 in the 1980 Edition (Winter 1980 Addenda) reads:
"For open ended portions of discharge lines beyond the last shutoff valve in nonclosed systems (e.g., service water system), confirmation of adequate flow during system operation shall be acceptable in lieu o'f system hydrostatic test." Footnote 1 to Article IWD-5223 reads:
"Open ended signifies free discharges that dissipate the transported fluid directly to the atmosphere (i.e., inside or outside containment structurel." Further guidance is offered under Class 2 requirements of that same Edition and Addenda.
Footnote I to Article IWC-5222(d) defines open ended as follows:
"...As an example, piping terminating in spray devices is considered open ended."
It is apparent that Section XI recognizes that hydrostatic testing of open ended systems, such as the spray and bypass piping downstream of the isolation valves, is not required to demonstrate the integrity of the piping system.
It should also be noted that that the system downstream of the isolation valves has been designed to 100 psig which represents a highly conservative design pressure in this portion of the system.
In addition, the new service water piping added under the scope of this proiect will be incorporated, as appropriate, into the existing inservice inspection program.
Licensee Proposed Alternative Examination Prior to initial operation of the new system, a flow test will be conducted to ensure that adequate flow capabilities exist to support design basis analyses. Welds in the spray and bypass piping will be 100% inspected by liquid penetrant methods in accordance with B31.7-1969 (with 1970 Addendal, Chapter 3-IV.
...- Staff Evaluation and Conclusions The subject section of the spray and bypass piping downstream of the isolation valves is an open ended system. As evidenced by the licensee's discussion above, it is impractical to isolate the open ended system for hydrostatic testing. Thus,Section XI requires only a confirmation of adequate flow during system operation.
This relief request is necessitated by the licensee's election to use the original construction code, according to Article IWA-7210 of Section XI, in the replacement of the Service Water System. The original construction code (ANSI B31.7-1969 Edition with Addenda through 1970) requires testing of nuclear piping according to ANSI B31.1-1967 Edition which does not exempt the subject open ended system from hydrostatic testing.
As an alternative to the 831.1 hydrostatic testing, the licensee will perform a flow test on the subject open ended system to confirm adequate flow according to Secton XI.
In addition, the licensee will perform surface examination of welds in the subject piping using liquid penetrant methods.
Based on the staff's evaluation and the licensee's discussion above, Code (R31.1) requirements are impractical.
It is further concluded that the alternative examinations discussed above will provide necessary added assurance of the Service Water System's structural reliability. Therefore, relief from the hydrostatic test requirements may be granted as requested.
Principal Contributor:
S. Lee
.