ML20212D741

Safety Evaluation Re Util 850827 Request for Relief from Hydrostatic Testing Requirements of ASME Code Section XI for Portions of Safety Injection Sys.Relief Justified

ML20212D741
Person / Time
Site:	Mcguire, McGuire
Issue date:	12/29/1986
From:	NRC
To:
Shared Package
ML20212D739	List: ML20212D733 ML20212D741
References
TAC-62269, TAC-62270, NUDOCS 8701050005
Download: ML20212D741 (5)

Text

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ENCLOSURE SAFETY EVALUATION OF REQUEST FOR RELIEF FROM RE0VIREMENTS OF ASME SECTION XI .

MCGilIRE, UNITS 1 AND 2 DUKE POWER COMPANY

By letter dated August 27, 1986, Duke Power Company (the licensee) requested

! relief from the ASME Boiler anet Pressure Vessel (R and PV) Code,Section XI, inservice hydrostatic test requirements on portions of the Safety Injection Systems for McGuire Nuclear Station, Units 1 and 2. The reason for this re-quest was that the licensee had determined that conformance with the Code hydrostatic test was impractical.

These Safety Injection (NI) System modifications involve replacing the dis-charge check valves for the cold leg accumulators. These valves also serve as a path for return flow to the Reactor Coolant (NC) System from the Decay Heat Removal (ND) System during a shutdown mode. A total of sixteen valves (2 per loop x 4 loops x 2 plants) will be replaced due to excessive seal and hinge pin wear.

Replacement of four of the check valves was performed during the recent Unit 1 end of cycle (EOC) 3 refueling outage (September 1986), with the remaining Unit I valves to be replaced during the next refueling outage (E0C A). It was initially intended to replace all of the valves in Unit 2 during E00-3.

Because these valves are currently not leaking, the replacement of the valves in Unit 2 will be postponed. It is, however, anticipated that replacement will be necessary within the current 10-year inspection plan interval. So, this relief evaluation is for both units.

Relief from hydrostatic testing has previously been granted for this same por-tion of the NI System for a similar modification (reference Mr. T.M. Novak's (NRC/0NRR) letter to Mr. H.R. Tucker (DPC) dated December 29,198?). -

Recause of the difficulties in performing h"hostatic tests on these portions of the systems, and the return of the syste a to operation in a timely schedule, the licensee requested this relief. The licensee stated that the alternate examinations specified in this relief request are equal to or better than the required testing per the Code.

The specific details on the requested relief are as follows:

1. The Specific ASME Code Section XI Requirement That Licensee Claims To Be Impractical ASME R and PV Code,Section XI, 1980 Edition through Winter 1980 Addenda, IWA - 4a00, IWR - 5000 requires a hydrostatic test to be performed following repair or replacement by weldino.

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2. Component For Which Relief Is Required:

A. Name and Numbers Units 1 and 2 Safety In.fection (NTI System primary and secondary check valves to the Reactor Coolant (NC) System (Reference Fig. I and 2 in the licensee's submittal) will be replaced.

B. Function The NI system provides emergenc.y core cooling to the Reactor Vessel. This particular portion of the system also provides a flow path for removal of decay heat in the shutdown condition, and is the primary flow path for the cold leg accumulators.

C. The ASME Section III Code Class is equivalent to Class 1 P. VALVE CATEGORY

1. The replacement valves are designed and fabricated in accordance with the ASME B&PV Code Section III - Class 1, 1983 Edition - Winter 1984 Addenda.

2. The valves are rated in accordance with ANSI B16.34-1981 1515 # special.

E. MATERIALS AND WELDS The materials used are:

1. 10" x 10" x 6" Reducing tee, schedule 140 x 160 (1.00" x

.718") SA-403 WP316 (P No. 8 Group li.

2. 10" 90* Elbow, Sch. 140, (1.00") SA-403 WP316 SMLS BW (P No. 8 Group 1).

3. 10" Pipe, Sch. 140, (1.00") SA 376 TP 316 (P No. 8 Group 1).

4. Valves, SA351 Grade CF8M (P No. 8 Group 1) (Reference Fig.

I and 2 in the licensee's submittali.

All welds are to be open root groove type utilizing a 37.5 5* bevel made to an IAN approved welding program. The root opening (1/8" 1/32") is to be filled by a minimum of two passes of gas tungsten are welding and finished up by shielded metal arc welding.

The reason that the licensee is recuesting relief is that there are no isolation valves downstream of these primary and secondary check valves to the NC system, therefore, it is impossible to isolete these portions of systems.

There are several approaches to partially pressurizino the system. The first approach would be to pressurize the Reactor Coolant (hC) System to 2,235 psi, and then use the Safety In,iection (NI) pumps to pressurize the NI Systems against one of the check valves. However, this pump pressure is only 1,600 psi, which falls far short of the required test pressure.

The second approach would be to remove the internals from the primary check valves which go to the NR System, and then pressurize the NC System to 1.02 times 2,236 pounds at 500 F temperature. However, this method would still not achieve the desired test pressure and temperature per the Code, because this portion of the system would be a dead leg pipe with no flow and uninsulated and, therefore, the convective and conductive effect of heat transfer would possibly make the 500 F temperature minimum unattainable.

This would also require draining the system in order to replace the internals in the check valve, a time consuming and costly procedure.

Therefore, due to orientation of the valves within the system, it is not possible to hydrostatically test the system. However, the alternate examinations as specified below are equal to or better than the required .

testing per the Code.

In lieu of the required hydrostatic test, the licensee has proposed to perform a 100% radiographic examination plus a 100% penetrant (PTT examination on the completion of all pressure boundary walds. A PT examination of all weld root passes will also be performed.

Also, a hydrostatic test will be performed at the 10-year inspection interval per Section XI of the ASME Code. An inservice leak test cannot be performed on this system because if the check valves hold, the system will not see system pressure. In addition, an ultrasonic (UT) examination will be performed on the welds for preservice baseline inspection per ASME Section XI.

The licensee has stated that these examinations, with the exception of the hydrostatic test, will be carried out after the modification on the Safety iniection (Nil System is complete, and prior to the system being declared operable.

Staff Evaluation: The relief reouest is acceptable for both Units 1 and 2 based on the following considerations.

1. Requiring the ASME Code hydrostatic tests to be performed at this time would result in a substantial additional manpower expenditure, additional occucational radiation exonsure, and possibly would delav plant startup. Therefore, hydrostatic testino at this time would result in hardships or unusual difficulties without a commensurate increase in the level of quality and safety.

2. Perforr:ance of the radiographic, surface, and ultrasonic examinations would oenonstrate e/Feuate structural integrity.

Duke Power Compery Frr ccrr;itted to performing the requirec 10-year intersel hycrcstatic tests which would irclude the niodifiec pcrtien of the NI system.

C0hCLUSIONS Relief from the inservice hydrottotic tests required by Section T! ic itstified.

The alternative rrogran, as proposed by Duke Power Coritary, of nor' destructive examinations ers bycrcstatic testing at prettritre 10-year intervals will pre -

vice at eccepte.ble level of structerei irtegrity. The specific requirener.it O' bection XI of the ASl'E Loiler tre Pressure Vessel Code,1980 Editiu. ttrcugh Winter ISEL l.ccci de , are impractical in this ce!.t . Ir/piercentation of the requirenients would rcsvit in hardships or unusual difficu'ities without a com-pensating increase it, the level of quality and safety. /ccr.roingly, the Cor.t,ission tts vetermined to grant relfe' froo the Lycrostatic test requite-rients as requested basec upoi the cct clusion that it is authorizet by 1to, l will ret endancer life or property or the conocn defense and security, nr.d *!

otterwise iri the public interest givei c'ue consideration to the burdar trcr the licensee that could resu't if the requirements were iraposed or tFr facility, l

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