ML18058A274
| ML18058A274 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/11/1992 |
| From: | Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.099, RTR-REGGD-1.099 NUDOCS 9203190034 | |
| Download: ML18058A274 (4) | |
Text
consumers Power POW ERIN&
MICHl&AN'S PRO&RESS Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 March 11, 1992~
Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 GB Slade General Manager DOCKET 50-255 - LICENSE DPR PALISADES PLANT - CORRECTION FACTOR FOR IRRADIATION TEMPERATURE BELOW 525°F - PRESSURIZED THERMAL SHOCK - 10CFR50.61 Section C.1.3 of Regulatory Guide (RG) 1.99, Revision 2, states that calculation procedures utilizing the equations in the Guide are valid for a nominal irradiation temperature of 550°F; and, that irradiation below 525°F should be considered to produce greater embrittlement and a correction factor justified by reference to actual data should be used.
A preliminary search of Palisades records indicated that, during Cycle 1 and half of Cycle 2, the plant operated with a T-average program which ranged linearly from 532°F at zero power to 544°F at full power.
At that time, core Delta-Twas 43°F at full power.
The program resulted in a full power T-Cold of 522.5°F and T-Cold being below 525°F when the power level was above approximately 70%.
Conservatively assuming all operation in the first cycle and half of the second cycle was at 100% would result in the following fluence being delivered to the vessel inner wall,,at 522.5°F:
- 1.
At 0 degrees vessel radial angle, f = 2.51El8 n/sq cm;
- 2.
At 16 degrees vessel radial angle, f = 3.31El8 n/sq cm; and
- 3.
At 30 degrees vessel radial angle, f = 2.57El8 n/sq cm.
Near the end of Cycle 2, the Palisades full power rating was increased from 2200 MWT to 2530 MWT and the T-Average program was increased at the same time.
~q For the next 7 cycles (Cycles 3-9) of approximately 12 effective full power
~
months each, T-Cold ranged from 536 to 539°F.
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' -9203190034 920311 PDR ADOCK 05000255 p
PDR PALISADES A OMS ENERGY COMPANY I r
We believe no correction factor should be applied to the embrittlement calculated for the fluence in~rement below 525°F for the following reasons:
2
- 1.
T-Cold was only 2.5°F below the 525°F lower irradiation temperature guideline.
Fluence of 2.57El8 at the limiting weld represents about 22%
of the fluence accumulated to date and about 15% of the estimated fluence at the 270°F screening limit for this weld.
Since the welds have had at least 7 effective full power years at temperatures above 525°F, it is expected that any extra damage caused by the 2.5°F difference early in life would be minimized by annealing which took place during the operation at higher temperatures later in life.
- 2.
Another approach which could be taken is to compute the weighted average irradiation temperature.
The timing of the lower temperature irradiation could be conservatively ignored and a fluence-weighted average irradiation temperature computed (assuming the longitudinal welds are limiting, the fluence at the screening criteria for the limiting weld is 2.07El9, and the present fluence is l.18El9).
The calculation is accomplished as follows:
Average Tc = [0.257El9(522.5)+0.923El9(536)+0.890El9(534)] / 2.07El9 Average Tc= 533.5 at the screening criteria limit; or Average Tc = [0.257El9(522.5)+0.923El9(536)] / l.18El9 Average Tc = 533.0 at the present time.
Therefore, since the fluence weighted average irradiation temperature is significantly greater than 525°F, no correction is necessary.
- 3.
Our understanding is that the correlations of 10CFR50.61 have been derived exclusively from data from power reactor surveillance specimens.
RG 1.99, Revision 2, Reference 2, lists 51 weld metal points which are all from older PWR's (except for the two Dresden Unit 3 points). There are 5 Babcock & Wilcox plants.
The remaining 44 plants are Westinghouse or Combustion Engineering. These plants typically run with Tc in the 525°F to 550°F range.
Power Reactors typically irradiate their vessel at Tc.
Although much research data is available at an irradiation temperature of 550°F, the center band of the power reactor surveillance data is likely to be in the 535°F to 540°F range.
Section 8.4 of RG 1.99 suggests a +/-25°F band be applied to surveillance data. This would extend the operating power reactor range to 510°F or 515°F.
Palisades is well within these limits.
- 4.
To address the requirement of RG 1.99, Section C.1.3.2, to refer to actual data, consider the surveillance program results for the RACO 3 W5214 heat.
There are 7 available points.
Of these, 3 were irradiated at 539°F and 2 were irradiated at 522°F.
All 7 points lie on a reasonably straight line and agree quite well with the 10CFR50.61 correlation if our proposed chemistry is assumed.
Thus, it is shown by test that, for the W5214 heat, irradiation at 522°F did not produce results outside the certainty allowance typically used to judge a qualified surveillance program.
.)
Furthermore, Palisades irradiation temperatures are bounded on both the high and the low sides by the surveillance data points.
If a chemistry factor is calculated for Heat W5214 from the measured shifts using the fitting procedure in Section C.2 of RG 1.99, a value of 217°F is determined. This agrees well with the value of 217°F calculated from our best estimate chemistry and the RG 1.99 tables. This is further evidence that in the range of temperatures we are considering, no correction is necessary.
The attached plot (Figure 1) illustrates this agreement.
3 The Palisades surveillance program contains specimens from plate D-3803-1.
The plate chemistry is 0.243 Cu and 0.513 Ni.
The chemistry among and within the Palisades plates is very consistent. The chemistry factor calculated by RG 1.99, Revision 2, for this plate is 159.
Irradiated Charpy specimens from the plate produced a shift of 155°F at a fluence of 1.09E19 and 230°F at a fluence of 4.40E19.
Applying the RG 1.99, Section C.2, procedure produces a chemistry factor of 161. This shows that samples exposed to the Palisades exact flux spectrum and T-Cold history agree well with the RG correlation without correction.
In view of the above reasons, we believe Palisades has satisfied the conditions of RG 1.99, Revision 2, Section C.1.3, and, as stated earlier, no additional correction is required to compensate for operation during Cycle 1 and part of Cycle 2 with Tc at 522.5°F.
Gerald B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment
- ~.
M~asured RT NDT Shift for Surveillance Data vs Calculated Using Palisades Chemistry
=
- -.c
(/)
"'C Cl)
- s Cl) as Cl)
- E 320 300 280 260
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~C8,,'
<c 240 btb~,,'
roro,,
220 200 180 160 140 120 100. ------!------'----'---'-----'--.......__---'--_"---__._____.
1 oo,_ 120 140 160 180 200 220 240 260 280 300 320
.* W5214
... 27204 Calculated Shift