ML20214U608
| ML20214U608 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 11/26/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214U562 | List: |
| References | |
| TAC-60596, NUDOCS 8612090322 | |
| Download: ML20214U608 (6) | |
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SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON REACTOR VESSEL PRESSURE-TEMPERATURE LIMITS WISCONSIN ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT UNIT 1 00CKET NO. 50-266 INTRODUCTION In a letter from R. W. Britt to H. R. Denton, dated Moy 16, 1985, the Wisconsir; Electric Power Company (the licensee) proposed the continued use of the Point Beach Unit I reactor vessel pressure-temperature limits specified in Figures 15.3.1-1 and 15.3.1-2 in the current plant Technical Specifications. The bases for the continued use of the temperature and pressure limits during heatup and cooldown are the test results from the Point Beach Unit 1 surveillance program contained in Reference 1.
DISCUSSION Pressure-temperature limits must be calculated in accordance with the requirements of Appendix G, 10 CFR 50, which became effective on July 26, 1983.
Pressure-temperature limits that are calculated in accordance with the requirements of Appendix G, 10 CFR 50, are dependent upon the initial reference temperature (RTNDT) for the limiting materials in the beltline and closure flange regions of the reactor vessel and the increase in RTNDT resulting from neutron irradiation damage to the limiting beltline material.
The Point Beach Unit I reactor vessel was procured to the ASME Code requirements which did specify fracture toughness testing to determine the initial RT for each vessel material. The licensee indicated in Reference 2 NDT that the initial RT for the limiting materials in the closure flange and NDT beltline regions of the Point Beach Unit 1 vessel was estimated using the method recommended by the staff in Branch Technical Position MTEB 5-2,
" Fracture Toughness Requirements", which is documented in the Standard Review Plan, Section 5.3.2, " Pressure-Temperature Limits".
8612090322 861126 PDR ADOCK 05000266 P
. The limiting beltline material is the weld metal which was fabricated using weld wire (heat no. 61782) ard Linde 80 flux (lot no. 8350) (Reference 3).
The licensee indicates that Branch Technical Position MTEB 5-2 results in ar.
initial RT f 30 F for this material (Reference 2). The chemical NDT composition of this material is given in References 2 through 5.
The licensee indicates that the limiting closure flange region material is the vessel head 0
flange, in which the initial RT is estimated as 50 F (Reference 2).
NDT The increase in RT resulting from neutron irradiation damage depends upon NDT the predicted amount of neutron fluence and the rate of embrittlement of the limiting reactor vessel beltline material. The licensee estimated that the neutron fluence at the inside surface of the limitino weld (15 ) will be I9 2
1.05 x 10 n/cm at 14 effective full power years (EFPY) (References 1 and 3).
The increase in RT resulting from neutron irradiation damage was estimated NDT by the licensee according to Regulatory Guide 1.99 Rev. 1, " Effects of Residual Elements on Predicted Radiation Damage to Reactor Vessel Materials".
Table 1 compares the observed increase in RT of the surveillance weld metal NDT to that predicted according to Regulatory Guide 1.99 Rev. 1.
The surveillance weld metal is not from the same heat of flux and wire as that used in the fabrication of the limiting beltline weld.
However, it may be used to evaluate the effect of irradiation on the beltline weld, since it was fabricated using the same type of flux and wire as the limiting beltline weld.
The surveillance material test results indicate that the increase in RT Of NDT surveillance weld metal is significantly less than that predicted by Regulatory Guide 1.99 Rev. 1.
Hence, the Regulatory Guide should provide a ccnservative estimate as to the amount of increase in RT resulting from NDT neutron, irradiation for the Point Beach Unit I limiting reactor vessel beltline weld.
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CONCLUSION 1
We;have used the unirradiated RT for beltline ard closure flange materials, NDT which were previously discussed, the neutron fluence estimates of'the licensee, the Regulatory Guide 1.99 Rev. I method of estimating neutron irradiation damage, and Standard Review Plan 5.3.2 method of calculating pressure-temperature limits to evaluate the licensee's proposed pressure-temperature limits.
Our evaluation indicates that the pressure-temperature limits in the current plant.
Technical Specifications meet the safety margins of Appendix G, 10 CFR 50, for a period of time corresponding to 14 FFPY. Hence, the staff concludes'that the licensee may continue to use the pressure-temperature' limit curves in the current plant Technical Specifications for Point Beach Unit 1.
Principal Contributors:
B. Elliot S.' Lee 1
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i TABLE 1 Comparison of Observed and Calculated Increase in RTNDT of k' eld Metal ir. Surveillance Capsules s
Surveillance Capsule Increase in RT Increase in RT Capsule Fluence Measured CalculatedUsih@T hDT R.G. 1 99 Rev. 1 (n/cm )
(U )
(O )
2 F
F 19 V
0.544x10 110 188 19 S
.0.755x10 165 222 19 R
2.08x10 165 320 I9
.T 2.11x10 180 330
,k i
- {
J.
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, REFERENCES (1) Westinghouse Report WCAP-10736, " Analysis of Capsule T From the' Wisconsin Electric Fower Company Point Beach huclear Plant Unit No. 1 Reactor Vessel Radiation Surveillance Program", S. E. Yanichko, V. A. Perone, and W. T. Kaiser, December 1984.
(2) Westinghouse Report WCAP-8743, "Heatup and Cocldown Limit Curves for the Wisconsin Electric Power Company and the Wisconsin Michigan Power Company Point Beach Nuclear Plant Unit No. 1", J. H. Phillips and O. Meeuwis, January 1977.
(3) Letter from C. W. Fay (Wisconsin Electric Power Company) to H. R. Denton (hRC), March 14, 1986, anc Westinghouse Report WCAP-10638, " Adjoint Flux Program for Point Beach Units 1 and 2", S. L. Anderson and K. R. Balkey, December 1984.
(4) Letter from C. W. Fay (Wisconsin Electric Power Company) to H. R. Denton (NRC), January 20, 1986.
(5) Letter frcm T. G. Colburn (NRC) to C. W. Fay (Wisconsin Electric Power.
Company), September 4,1986.
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