ML20235F506

Safety Evaluation Re Review of Licensee 870806 & 27 Proposed Changes to B&W Owners Group Integrated Reactor Vessel Matl Surveillance Program.Proposed Changes Acceptable

ML20235F506
Person / Time
Issue date:	09/18/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235F496	List: ML20235F493 ML20235F506
References
NUDOCS 8709290163
Download: ML20235F506 (2)

Text

_ _ _______ _ _ _ - __-___ _-

M ENCLOSURE E SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION h

REVIEW 0F A PROPOSED REVISION TO THE 88W OWNER'S GROUP INTEGRATED SURVEIL _ LANCE PROGRAM TAC NO.# 65927 MATERIALS ENGINEERING BRANCH DIVISION OF ENGINEERING _AN_D _ SYSTEMS TECHNOLOGY Backgrou_nd The Babcock & Wilco- 'B&W) Owners Group proposed an integrated reactor vessel surveillance progra... .or Oconee, Units 1, 2 and 3; Arkansas Nuclear One.

Unit 1; Ranch Seco; Three Mile Island, Unit 1; Three Mile Island, Unit 2; Midland, Unit 1; Davis Besse Unit 1; and Crystal River, Unit 3 plants. In this program, reactor vessel surveillance capsules from all the participating owners, except Consumers Power Co., were to be irradiated inside the reactor vessels at Davis Besse and Crystal River. The integrated surveillance program was documented in Report' BAW-1543, Rev. 2, February 1984, " Integrated Reactor Vessel Material Surveillance Program." The staff's review of the integrated program is documented in a letter from C.0. Thomas to J. H. Taylor, dated March 15, 1985. The staff approved the integrated program for all participating

' plants, except Three Mile Island, Unit 2 and Midland, Unit 1.

The regulatory requirements for an integrated material surveillance program are documented in 10 CFR 50, Appendix H. This appendix indicates that the material surveillance program is required to monitor changes in the fracture toughness properties of ferritic reactor vessel beltline material:, resulting from exposure of these materials to neutron irradiation and the thermal environment.

Discussion In letters to T. E. Murley dated August 6, 1987 and August 27, 1987, B&W, acting for the owners group proposed changes to the owners group integrated reactor vessel surveillance program. The changes include a revised surveillance capsule insertion and withdrawal schedule and deletion of Capsule TNI-1A from the program.

The changes to the capsule withdrawal schedule were needed because of changes to the end-of-life calculated neutron exposures of the participating vessels and the calculated neutron exposures at the capsule holder positions. Changes in calculated neutron exposures result from plants using low leakage cores and more accurate neutron fluence determinations. Except for TMI-1, end of life neutron fluence values were previously reported in Report BAW-1895, 8709290163 070918 PDR TOPRP ENVBW C PDR <

a .3 l

t

" Pressurized Thermal Shock Evaluation in Accordance with 10 CFR 50.61 for Babcock & Wilcox Owners Group Reactor Pressure Vessels." TMI-1 values were modified consistent with the.results of Report BAW-1901, " Analysis of Capsule TMI-1C GPU Nuclear Three Mile Island Nuclear Station Unit 1," March 1986.

The B&W method of calculating neutron fluence and owners group plants end of life neutron fluence values were reviewed by the staff in its evaluation of the PTS issue and owners group surveillance capsules.

The Owners Group proposes that Capsule THI-1A be destructively examined to requalify the TMI-2 B&W Owners Group surveillance capsules. TMI-1A was one of six capsules removed from the THI-2 reactor. Capsules TMI-1A and TMI-2 LG2 ,

(both in the ZY holder tube location) represent the " worse case" capsules {

based on the condition of the temperature monitors obtained by radiography. '

These two capsules experienced a similar thermal environment, which appears to be hotter than the other holder tube locations. The TMI-1A capsule contains Charpy V notch and ter.sile specimen. Since the TMI-2 LG2 capsule contains Charpy V notch, tensile and compact fracture toughness specimens, the TMI-2 LG2 capsule will provide substantially more useful fracture t6ughness data than the TMI-1A capsule. l Capsule TMI-1A contains weld metal WF-25, which is one of the materials in the beltline region of THI-1. In addition to capsules TMI-10 and TMI-1E, weld metal WF-25 is also contained in Owners Group Capsules CR3-LG1, TMI-2LG2 and THI-2LG1. The Owners Group capsules also contain weld metal SA-1526, which was made with the same heat of filler wire used to fabricate WF 25 weldments.

The filler wire contributes residual elements to the weldment. Staff studies -

indicate that the residual elements in the filler wire contribute to the neutron irradiation damage to the weldment. Since SA-1526 and WF-25 weldments were made with the same filler wire, the SA-1526 surveillance welds will provide data on the effect of neutron irradiation on WF-25 weld metal.

Although the weld metal in TNI-1A will not be irradiated and tested, as planned, the owners group prog im contains other sources of weld metal, which can be used to replace the THI-1A capsule weld metal.

Conclusions

1. Since Owners Group capsules can provide more useful fracture toughness data than the TMI-1A capsule and the effect of neutron irradiation on TM1-1A weld metal can be evaluated from material in other surveillance capsules, the TMI-1A capsule may be used to requalify the TMI-2 Owners Group surveillance capsules.

2. The integrated reactor vessel materials surveillance program documented in Report BAW-1543A, Rev. 2 and revised in accordance with B&W 1etters dated August 6,1987 and August 27, 1987 will be capable of monitoring the effect of neutron irradiation and the thermal environment on the fracture toughness of the ferritic reactor vessel beltline materials in the plants participating in the integrated material surveillance program.

3. Based on conclusions 1 and 2 above, the changes to the integrated )

surveillance program documented in B&W letters dated August 6,1987 and August 27, 1987 are acceptable.