ML16342D988
| ML16342D988 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 02/10/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16342D987 | List: |
| References | |
| NUDOCS 9802240012 | |
| Download: ML16342D988 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&4001 AFETY EV L N
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KET N 1,0 In a letter dated October 22, 1997, Pacific Gas and Electric Company (PG8E) submitted, for NRC approval, their proposed reactor vessel surveillance capsule withdrawal schedule, which was based on the American Society for Testing and Materials (ASTM) E185-73 and E185-82 recommendations and reflected updated fluence information from the surveillance capsule removed in 1994 from Diablo Canyon Unit 2.
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R ND The surveillance program for Diablo Canyon Unit 2 was implemented to monitor the radiation-induced changes in the mechanical and impact properties of the pressure vessel materials.
This surveillance program was established in accordance with 10 CFR Part 50, Appendix H, and ASTM E185-73.
By letter dated October 11, 1994, and WCAP-14363, the licensee provided a recommended revised surveillance capsule withdrawal schedule for Diablo Canyon Unit 2. The recommended revision to the capsule withdrawal schedule was a result of revised surveillance capsule location lead factors. The updated lead factors accounted for the dosimetry results of all the Unit 2 surveillance capsules evaluated to date, which minimized the uncertainty associated with any specific capsule dosimetry set.
By letter dated October 4, 1995, PG&E submitted the results of the reactor vessel surveillance Capsule Y, which was removed from Diablo Canyon Unit 2 on October 11, 1994.
Based on the capsule test results, a recommended revised surveillance capsule withdrawal schedule was provided by the licensee in WCAP-14363, Table 7-1. The recommended revision to the capsule withdrawal schedule was a result of revised surveillance capsule location lead factors.
The updated lead factors accounted for the dosimetry results of all the Unit 2 surveillance capsules evaluated to date.
By letter dated November 25, 1996, PG8E provided the revised FSAR Update Table 5.2-22, "Reactor Vessel Material Surveillance Program Withdrawal Schedule," which was based on the results of WCAP-14363. The revised capsule withdrawal schedule is equivalent to 98022400i2 9802i0 PDR ADQCK 05000323 P
WCAP-14363, Table 7-1, except that Capsules V and Z are also scheduled for removal.
PG8 E also explained that Capsules V, W, and Z have identical contents, similar lead factors, and will achieve the fluence equivalent to a vessel service of 60 operating years at approximately the Unit 2 ninth refueling outage (2R9). The licensee stated that there was no technical justification for additional capsule irradiation. To avoid excessive radiation damage to the capsule components and facilitate scheduling and handling, PGKE has planned to remove all three capsules, V, W, and Z, during 2R9. Following 2R9, Capsule V willbe tested in accordance with ASTM E-185-82 and 10 CFR 50, Appendix H, and Capsules W and Z willbe stored in the spent fuel pool as available spares ifneeded to address future contingencies.
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Appendix H to 10 CFR Part 50, "Reactor Vessel Material Surveillance Program Requirements,"
include criteria to monitor changes in the fracture toughness properties of ferritic materials in the reactor vessel beltline region of light water nuclear power reactors which result from exposure of these materials to neutron irradiation and the thermal environment.
Appendix H to 10 CFR Part 50 endorses ASTM E185, "Surveillance Tests for Nuclear Reactor Vessels."
Appendix H states that "the design of the surveillance program and the withdrawal schedule must meet the requirements of the edition of ASTM E185 that is current on the issue date of the ASME Code to which the reactor vessel was purchased."
As indicated in the Diablo Canyon Unit 2 Final Safety Analysis Report Update, the Diablo Canyon Unit 2 surveillance program complies with 10 CFR Part 50, Appendix H, and ASTM E185-73.
Because this edition of the standard was current at the time the reactor vessel was purchased, the Diablo Canyon Unit 2 surveillance capsule withdrawal schedule satisfies the requirements of Appendix H to 10 CFR Part 50.
In addition, the licensee has implemented the ASTM E185-82 Standard, to the maximum extent possible, for the Diablo Canyon Unit 2 withdrawal schedule.
Descriptions of how the withdrawal schedule for Diablo Canyon Unit 2 meets the recommendations of the ASTM E185-73 Standard and the ASTM E185-82 Standard are provided below.~
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Vessels" By ASTM E185-73, it is recommended that the capsules be withdrawn according to application by either one of these cases:
Case A - where both the predicted increase in transition temperature of the reactor vessel steel is 100 F or less and the calculated peak neutron fluence (E > 1 MeV) of the reactor vessel is 5 x 10" n/cm'r less or Case B - where the predicted increase in transition temperature of the reactor vessel steel is greater than 100'F or where the calculated peak neutron fluence (E > 1 MeV) of the reactor vessel is greater than 5x10" n/cm'.
Case B applies to the Diablo Canyon Unit 2 surveillance program.
Currently, the licensee has tested 3 capsules for Diablo Canyon Unit 2: (1) Capsule U was tested at a fluence of 0.36E19 n/cm', which corresponded to an RTQ7 shift of approximately 50'F, (2) Capsule X was tested at 0.87E19 n/cm', which corresponded to the calculated exposure of the reactor vessel wall at approximately 50% to 75% of the reactor design life, and
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1 (3) Capsule Y was tested at 1.32E19 n/cm', which corresponded to the calculated exposure of the reactor vessel wall at approximately 100% to 125% of the reactor design life. Capsules W and Z are standby capsules.
The staff verified that the proposed withdrawal schedule for Diablo Canyon Unit 2 is in accordance with Case B of ASTM E185-73.
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Vessels" By ASTM E 185-82, the minimum recommended number of surveillance capsules to be withdrawn and tested depends upon the predicted transition temperature shift at the vessel inside surface.
The predicted transition temperature shift at the vessel inside surface for Diablo Canyon. Unit 2 is greater than 200 F; therefore, by ASTM E 185-82, it is recommended that 5 capsules are withdrawn/tested.
Capsule U was tested at a fluence of 0.36E19 n/cm', which corresponded to an RT,>> shift of approximately 50'F, Capsule X was tested at 0.87E19 n/cm', which corresponded to 3 EFPY and to the EOL fluence at the reactor vessel 1/4t location, and Capsule Y was tested at 1.32E19 n/cm', which corresponded approximately to the EOL fluence at the vessel ID. PGKE has scheduled the testing of Capsule V at a projected fluence of approximately 2.2E19 n/cm',
which corresponds to 1.5 times the EOL fluence at the vessel ID. In addition, PG8 E has 2 standby capsules, Capsules W and Z, that willbe stored in the spent fuel pool upon removal.
The staff verified that the proposed withdrawal schedule for Diablo Canyon Unit 2 is in accordance with ASTM E185-82 to the maximum extent possible.
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Based on the staffs review of the PG8 E submittal, the staff found that the revised withdrawal schedule is acceptable for Diablo Canyon Unit 2. The proposed withdrawal schedule satisfies the ASTM E 185-73 Standard.
Since this edition of the standard was current at the time the reactor vessel was purchased, the Diablo Canyon Unit 2 surveillance capsule withdrawal schedule satisfies the requirements of Appendix H to 10 CFR Part 50. Therefore, the staff approves the revised withdrawal schedule for Diablo Canyon Unit 2.
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T CAPSULE TARGET FLUENCE STATUS U
V W
3.6E18 8.7E18 1.32E19 2.2E19 TESTED TESTED TESTED TO BE TESTED STANDBY STANDBY
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