ML18052B469
| ML18052B469 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 01/20/1988 |
| From: | Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8801270039 | |
| Download: ML18052B469 (7) | |
Text
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NllCHlliAN'S PROliRESS General Offices: 1945 West Parnell Road, Jackson, Ml 49201 * (517) 788-0550 January 20, 1988 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
LOW TEMPERATURE OVERPRESSURE PROTECTION (LTOP)
Consumers Power. Company's letter dated December 22, 1987 proposed new Technical Specifications which extend the temperature range over which LTOP is provided and require new PORV setpoints to assure Low Temperature Overpressure Protection (LTOP).
Additionally, it proposed to require the High Pressure Safety Injection (HPSI) pumps to be inoperable, when the PCS temperature is less than 430°F, to prevent a pressure incre~se caused by their inadvertent start.
Preliminary review of our December 22, 1987 proposed Technical Specification Changes by the NRC staff resulted in concern that with the HPSI pumps inoperable when PCS temperature is less than 430°F, there would be no analyzed method, while heating up or cooling down, of protecting the core during LOCA's of certain sizes.
It is our understanding that existing regulations do not require ensuring by analysis that there would be no core damage caused by a LOCA when the reactor is subcritical.
However, we have completed analyses (Reference 1), which shows the potential for sub-critical core damage.caused by a LOCA during heatup or cooldown can be minimized and, at the same time, the PCS can be protected from overpressure.
The potential for LOCA caused core damage is minimized by keeping one HPSI train operable above 350°F.
LTOP is provided by a combination of administratively controlled heatup/cooldown rates, PORV settings, and the addition of a dedicated operator during heatup and cooldown when the PCS cold leg temperature is less than 430°F and the PORVs are inoperable.
The 10CFR50 Appendix G pressure/temperature heatup limits used in our Reference 1 analysis are recently calculated and are based on recently revised 10CFR50 Appendix G pressure/temperature limits which have unnecessary conservatisms removed.
Use of these new pressure/temperature limits in our analyses.has been reviewed and informally approved by the NRC staff.
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OC0188-0013A-NLUZ" L]
Nuclear Regulatory Commission Palisades Plant Low Temperature Overpressure Protection January 20, 1988 attachment to this letter describes the new pressure/temperature limits.
Before June 1, 1988, we will propose a Technical Specification Change to include the new heatup limits in the Palisades Technical Specifications.
We also plan to submit a revision to our December 22, 1987 proposed LTOP Technical Specification Change.
The LTOP revision will delete proposed Section 3.3.2 G, which requires both HPSI pump control fuses to be removed when PCS temperature is less than 430°F, and will add the requirement to keep one HPSI pump operable when PCS temperature is greater than 350°F.
2 Therefore, until the December 22, 1987 proposed Technical Specification Change concerning LTOP, revised as described above, is approved, we shall operate the Palisades Plant as described in the December 22, 1987 proposed LTOP Technical Specification Change, except that both HPSI pump control fuses will not be removed, one HPSI control fuse will remain installed when PCS temperature is above 350°F, i.e. a HPSI pump will be operable when the PCS temperature is above 350°F.
Additionally, whenever PCS temperature is less than *or equal to 430°F and a PORV is not armed, a d~dicated licensed operator shall be stationed in the control room to terminate an inadvertent HPSI pump start and stop charging pumps as necessary to limit PCS pressure.
Use of a dedicated operator enlarges the pressure window at 430°F from 70 psi to 400 psi and thus facilitates operation without proximity to either the Appendix G limits or the 25°F subcooling limits.
Appropriate procedure changes will be completed and plant operators made familiar with any new requirements before startup from the present outage.
Richard W Smedley Staff Licensing Engineer CC Administrator, Region III, NRC NRC Resident Inspector - Palisades Reference 1 - EA-PAL-LTOP-880119 and EA-PAL-LTOP-880120 - "Revision of Palisades Plant Heatup Curves" OC0188-0013A-NL02
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IC0188-0013A-NL02 ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 REVISION OF PALISADES PLANT HEATUP CURVES January 20, 1988 4 Pages
.. 1.
Revision of Palisades Plant Heatup Curves The heatup curves for Palisades have typically been developed incorporating the ~Tmax term into the stress intensity calculations for both the l/4T and 3/4T flaw locations in the beltline wall.
For the 3/4T location, the inclusion* is appropriate because the 3/4T location experiences tension due to the thermal gradient.
The inclusion of the 6.. Tmax term for the l/4T location is unnecessary and is regarded as an oversight.
That is because the
. l/4T location. experiences compression rather than tension.
Although it *is. not judged practical to attempt to take credit for compressive thermal stress to cancel out primary pressure tensile stress, it does seem appropriate to employ a value of zero for~Tmax when calculating allowable pressure for a given temperature and heatup rate at the l/4T location.
That approach has been adopted in the attached data and represents the only departure from the calculations associated with the last Palisades Plant Technical Specification change for heatup and cooldown curves for the primary coolant system.
Table I reflects the results of calculations for the revised heatup curves.
The 3/4T data are as before.
For low temperatures and very high heatup rates, some of the. allowable pressures have little practical or operational significance.
The heatup curve for the l/4T location has changed from before because of the A T=O assumption.
Table II reflects limiting allowable pressures as taken from the l/4T and 3/4T data from Table I. It r.epresents a sorting.
The trend s.ays that the l/4T location can control on material properties at higher temperatures and lower heatup rates.
The 3/4T location controls on stress at lower temperatures and higher heatup rates.
The severity of the l/4T allowable pressures is somewhat overstated because. compression has not been accounted for at that thi.ckness location.
To do so would require the operator to ensure that the heatup rate was at least as high as charted because it is the heatup rate that is providing the benefit of compression.
Such considerations may be addressed when reviewing the impact of excursions from the curves.
However, thermal compression has not been used in deriving them~
Table III represents the composite of wall locations to characterize operating limits.
These should be included in the Technical Specific~on~
(.
Palisades Plant Heatup Curves (PCS)
J. Nicholas Gould 01-14-88 Revised Heatup Curves Table III Heat Up - Longitudinal Weld - Limit
~---------~-----------------~--------
.Heat Up
- Rate degF/HR 0
20
- 40 60 80 100 50 402 328 241 159 75.
100 150 415 444 354 409 263,308 177 215 90 121 10 36 Degrees F 200 250 300 350 400 450 502 623. 873 1389 2454 4654 492 603 831 1302 2274 42_81 401 585 793 1224 2114 3952 293. 453 761 1157'.
1975 3664 186 319 594 1092 1841 338.7 90 202 434.
913 1726 3149
Palisades Plant Heatup Curves (PCS)
J; Nicholas Goul~
- ol-14-88 Revised Heatup Cu~ves Table I Heat Up - Longitudinal Weld -
1/4 T Heat Up 1/4 D. T Degrees F Rate Wall degF/HR Location AT (Max. )
50 100 150 200 250 300 350 400 0
20 40 60 80 100 1/4 1/4 1/4 1/4 1/4 1/4 0.0 6.3 12.4 18.2 24.3 30.0 0.0 402 0.0 400 0.0. 399 0.0 399 0.0 398 0.0 397 415 413 411 409 407 406 444 502 439 492 435 484 431 476 427 469 424 462 623 873 603 831 585 793 569 761 554 729 541 702 1389 1302 1224 1157 1092 1036 2454 2274 2114 1975 1841 1726 45C 4654 4281 3952 3664 3387 3149 Heat Up - Longitudinal Weld -
3/4 T Heat Up 3/4
~T Rate Wall degF/HR Location AT (Max.)
0 20 40 60 80 100 3/4 3/4 3/4.
3/4 3/4 3/4 0.0 13.3 26.3 38.6 51.4 63.2 0.0 14.2 28.0
- 41. 1 54.7 67.3 Degrees F 50 100 150 200 250 300 419 328 241 159 75 450 354 263 177 90 10 516 652 409 521 308 401 215. 293 121 186 36 90 933 752 592 453*
319 202 1512 1230 988 784 594 434 350 2708 2216 1805 1467 1161 913 400 5178 4253 3492 2879 2334 1900 450 10278 8458 6974 5792 4754 3940
- /.
Palisades Plant Heatup Curves (PCS)
Revised Heatup Curves Table II J. Nicholas Gould 01-14-88 Heat Up - Longitudinal Weld - Limit
-~------------------------------- ----------------------------------------------
Heat Up
~T Degrees F Rate Wall degF/HR Loca.tion A. T c Max.)
50 100 150 200 250 300 0
20 40 60 80 1/4
.. 1/4 1/4 1/4 0.0 6.3.
12*. 4 0.0 402 0.0 100 0
20 40 60 ao 100
'1/4 1/4 3/4
. 3/4 3/4.
3/4 3/4 3/4 18.2 24.**3 30.0 0.0 13.3.
.26. 3 38.6
- 51. 4 63.2 0.0 0.0 0.0 0.0 0.0 14.2
- 20. o
- 41. 1 54.7 67.3 328 241 159 75 415 354 263 177 90 10 444 409.
502 492 308 401 215 293
- 121 186 36 90 623 603 585 453 319 202 873 831 793 761 594 434 350.
400 450 1389 1302 1224 1.157 1092
_913 2454 2274 2114 1975
- 1841
-1726 4654 4281 3952 366.4
. 3387
- 3149