ML20080P349
| ML20080P349 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/02/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20080P342 | List: |
| References | |
| NUDOCS 9503070326 | |
| Download: ML20080P349 (6) | |
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SAFETY EVALUATION BY THE OFFICE ~0F NUCLEAR REACTOR REGULATION
- RELATED TO AMENDMENT NO.163 TO FACILITY OPERATING LICENSE NO.' DPR-20 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET NO. 50-255
1.0 INTRODUCTION
By'1etter dated October 5, 1994, as supplemented February 10, 20 and 22,-1995, the Consumers Power Company (CPCo or the licensee)~ requested an amendment to i
the Technical Specifications (TS) appended to Facility Operating License No.
DPR-20 for the Palisades' Plant. The proposed amendment would revise primary coolant system (PCS) pressure-temperature (P-T) limits, power-operated relief valve (PCRV) setting limits, and primary coolant pump (PCP)-starting limits to accommodate reactor vessel fluence for an additional 4 effective full power years (EFPY). The amendment would also revise the emergency core cooling system TS to render two high-pressure safety injection (HPSI) pumps incapable of. injecting into the PCS when the PCS is below 300*F rather than rendering both inoperable below 260*F.
In' addition, it would revise.the pressurizer heatup to achieve consistency between design _ assumptions and.TS limits.
The licensee's P-T limits were prepared from embrittlement estimates that were based on the data that was available prior to October 5, '1994. Subsequent to that date, the licensee gathered additional data that affected its embrittlement estimates. The additional data was provided to the staff at a meeting in NRC headquarters en November 21, 1994..-These data were provided to-the staff as part of the licensee's recent pressurized thermal shock (PTS) evaluation. Since the additional data affect the embrittlement estimates for '
the Palisades reactor vessel, the staff has included the data from the PTS evaluation in its assessment of the proposed Palisades P-T limits. The February 10, 20, and 22,1995, submittals provided clarifying information and-I a revised figure 3-4 that was more restrictive. Therefore, these submittals i
provided information that was within the scope of the initial application and did not affect the staff's initial proposed no significant hazards consideration findings.
2.0 EVALUATION 2.1 P-T Limits j
The staff evaluates the P-T limits based on the following NRC regulations and j
guidance: Appendix G to 10 CFR Part 50; Generic Letters (GL) 88-11 and 92-01, i
Regulatory Guide (RG) 1.99, Rev. 2; and Standard Review Pirn (SRP) Section 5.3.2.
Appendix G to 10 CFR Part 50 requires that P-T limits for the reactor p
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w.- vessel must be'at least as conservative as those obtained by Appendix G to Section III of the American Society of Mechanical Engineers (ASME)~ Code, i
GL 88-11 requires that licensees use the methods in RG 1.99, Rev. 2 to i
predict the effect of neutron'. irradiation by calculating the adjusted
.j reference temperature (ART) of reactor vessel materials. The ART is defined as the sum of initial reference temperature (RTm) of. the material ~, the mean
'value for the adjustment in RT,the initial RTcaused by neutron irradiation, and a margin.
toaccountforuncertaintiesi!E
, percent nickel, copper, neutron fluence and calculational procedures. The mean value for the l
adjustment in RT
-is calculated from the product of a chemistry factor.and 'a fluence factor. The chemistry factor is dependent upon the amount of copper and nickel in the vessel material. GL 92-01 requires licensees to submit reactor vessel maters 1s data, which the staff will use in the review of the J
P-T limits.
SRP 5.3.2 provides guidance on calculation of the P-T limits i
using the linear elastic fracture mechanics methodology specified in Appendix G to Section_III of the ASME Code. The linear elastic fracture-i mechanics methodology specified in Appendix G to Section III of the ASME Code requires that the analysis be performed using postulated sharp surface defects j
that are normal to the direction of maximum stress and have a depth of one-fourth of the section thickness (1/4T) and a length of 1 1/2 the section thickness. The critical locations in the vessel for this methodology is the-1/4T and 3/4T locations, which correspond to the maximum depth of the postulated inside surface and outside surface defects, respectively.
The licensee's P-T limit evaluation determined the adjusted reference temperature caused by radiation in accordance with the methodology in RG 1.99, Revision 2.
In this methodology, the adjustment in reference temperature is dependent upon the neutron fluence and the amounts of copper and nickel in the material.
The adjustment in reference temperature was determined using the best-estimate amounts of copper for the Palisades reactor vessel materials that were available on October 5,1994. The licensee's evaluation did not include the chemical composition data provided subsequent to that date. These additional data affected the projected amount of embrittlement for welds fabricated using heat numbers 34B009 and W-5214 weld wire.
The effect of radiation on the Palisades reactor vessel was evaluated during the staff's assessment of the licensee's PTS evaluation. The staff's PTS assessment indicates that the Palisades reactor vessel was fabricated by Combustion Engineering and that the limiting material with respect to PTS in the Palisades reactor vessel beltline is the axial weld fabricated using weld wire heat number W-5214. The Palisades reactor vessel beltline also contains axial welds fabricated using weld wire heat number 34B009 and a circumferential weld fabricated using weld wire heat number 27204.
As part of its PTS evaluation, the licensee detemined the best-estimate value of the percent copper and nickel from surrogate weld data that were fabricated-using the same weld wire heat number as the Palisades beltline welds. These data indicate that the best-estimate for the percent copper and nickel are:
(a) 0.212% copper and 1.02% nickel for weld wire heat number W-5214, (b) 0.19%
copper and 0.99% nickel for weld wire heat number 348009, and (c)'O.208%
copper and 1.00% nickel for weld wire heat number 27204. These values of
4 copper and nickel result in chemistry factors of:
(a) 232*F for weld wire heat number W-5214, (b) 219'F for weld wire heat number 34B009, and (c) 228'F for weld wire heat number 27204.
l The surrogate weld chemistry data for heat number W-5214 weld wire indicated a large variability in the_ percent copper and percent nickel. After considering the large variability in percent copper and nickel, the limiting weld is the weld fabricated using weld wire heat number 27204,,since it has the highest ART of 255*F and 191 F at the 1/4T and-3/4T locations, respectively. _This weld is not limiting for PTS because it is a circumferentially oriented weld and is further from the screening criteria in the PTS rule than the heat i
number W-5214 weld.
Substituting the limiting ARTS into equations in SRP 5.3.2, the staff verified that the proposed P-1 limits satisfy the requirements in paragraphs IV.A.2 and IV.A.3 of Appendix G of 10 CFR Part 50.
In addition to beltline materials, Appendix G of 10 CFR Part 50 also imposes a minimum temperature at the closure head flange based on the reference temperature for the flange material.
Section IV.A.2 of Appendix G states that when the pressure exceeds 20% of the preservice system hydrostatic test pressure, the temperature of the closure flange regions highly stressed by the bolt preload must exceed the reference temperature of the material in those regions by at least 120*F for normal operation and by 90*F for. hydrostatic pressure tests and leak tests. Based on the flange RT of 40*F, the staff hasdeterminedthattheproposedP-Tlimitshavesatis71'edtherequirementfor the closure flange region during normal operation, hydrostatic pressure test and leak test.
i The licensee's P-T limit evaluation determined the adjusted reference temperature caused by radiation in accordance with the methodology in RG 1.99, Revision 2, and the data available prior to October 5,1994. The staff reviewed this data and questioned what effect the additional data would have on the evaluation.
In response, the licensee stated that the new data would not affect the results. The licensee will resubmit its technical assessment of the P-T limits based on the data submitted as part of its PTS evaluation before May 1, 1995, to confirm the conclusions stated in the February 22, 1995, letter.
The staff has performed an independent analysis to verify the licensee's proposed P-T limits, cnd reviewed the chemical composition data from PTS discussions during the November 21, 1994, meeting.
The staff concludes that the proposed P-T limits for heatup and cooldown are valid for a neutron 2
fluence at the limiting weld of 2.192E19 n/cm, which corresponds to 6 EFPY t
from the beginning of cycle 10 because (1) the limits conform to the i
requirements of Appendix G of 10 CFR Part 50 and GL 38-11, and (2) the material properties and chemistry used in calculating the P-T limits are consistent with data submitted as part of the licensee's PTS evaluation and the staff's PTS assessment. Hence, the proposed P-T limits may be incorporated into the Palisades TSs.
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2.2 PORV Settino Limit. PCP Startino limit and HPSI Pump Restrictions The PCS P-T limits during plant heatup and cooldown for Palisades Plant are specified in TS Figures 3-1 and 3-2.
The existing PCS P-T limits were calculated for a reactor vessel wall fluence of 1.8 x 10"nyt. The pressurizer PORVs are used for overpressure mitigation against an inadvertent mass addition or energy addition event during low-temperature operating conditions. The PORV setpoints are specified in TS Figure 3-4 which assures that the transient peak PCS pressure are within the P-T limits specified in Figures 3-1 and 3-2.
Restrictions for starting the first PCP'are specified in TS 3.1.lh.
These restrictions would ensure that the PCS P-T limits are protected against an energy addition event while the secondary side temperature is more than 100*F hotter than the PCS temperature. TS 3.1.lh also ensures the closure of shutdown cooling system isolation valves prior to forced circulation to protect the shutdown cooling system from exceeding its pressure limit.
Limitations for HPSI pump operability during low temperature operation conditions are specified in TS 3.3 which would eliminate the potential mass addition from the HPSI pumps during an inadvertent safety injection actuation.
CPCo proposed changes to the P-T curves in TS Figures 3-1 (for heatup) and 3-2 (for cooldown), to TS Figure 3-4 (for PORV setpoints), to TS 3.1.lh (for starting first PCP), and to TS 3.3 (for HPSI pump operability).
The licensee states that the existing PCS P-T limits were based on a reactor vessel wall fluence of 1.8x10"nvt.
The changes in TS 3.1.1h and TS Figure 3-4 are intended to protect against P-T limits specified in the revised TS Figures 3-1 and 3-2.
The revised TS 3.3 would allow the HPSI pumps to remain operable during low temperature operating conditions so that these pumps could be manually actuated for PCS makeup in case the shutdown cooling capability is lost.
However, when the PCS temperatuare is less than 300'F, the HPSI pumps would be rendered incapable of injection into the PCS by manually interrupting the power supplies to HPSI pumps or by isolating the flow path.
In the current TS, when the temperature of the PCS cold leg is less than or equal to 430'F with the reactor vessel head unremoved, low temperature overpressurization is protected by either of the pressurizer PORVs with lift settings specified in TS Figure 3-4.
These settings were developed to avoid PCS pressure from exceeding the PCS P-T limits which were developed per the requirements of ln CFR Part 50, Appendix G.
The new PORY settings were determined ising the proposed PCS P-T limits and the ASME Code Case N-514 which allows the maximum allowable P-T limits to be '10% above the P-T limits specified in the revised TS Figures 3-1 and 3-2.
Since the ASME Code Case N-514 has not been officially endorsed by NRC, the licensee submitted an exemption request on February 10, 1995. On March 2, 1995, the staff approved an exemption from the requirements of 10 CFR Part 50, Appendix G, so that the Palisades Plant could take this needed 10% allowance in the maximum allowable P-T limits to avoid operational difficulties at Palisades.
The most limiting mass addition transient assumed in the licensee's analysis is an inadvertent safety injection actuation with the letdown system isolated.
i For PCS temperature above 300*F, the mass input from two HPSI pumps and three F
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charging pumps was assumed following a safety injection actuation.
For PCS temperature below 300*F the mass input from three charging pumps was assumed.
This is consistent with the revised TS 3.3 which requires that both HPSI pumps he rendered incapable of injection into the PCS. The new analysis incorporates additional conservatisms in the areas of the assumed PCS volume, charging flow and HPSI flow rate.
The most limiting energy addition transient assumed in the licensee's analysis is the start of the first idle PCP with secondary system temperature less than 100*F above the PCS cold leg temperature. The results of the analysis indicates that the transient PCS peak pressures are below their allowable P-T limits under isothermal conditions. The PCS was assumed in water solid condition prior to the transient for added conservatism in the licensee's analysis to support the proposed PORV settings.
The current TS 3.1.lh specifies the restriction of starting the first idle PCP at various PCS temperatures. The licensee proposed a revised TS 3.1.1h which would provide more generalized starting conditions for the first idle PCP.
The revised PCP starting criteria are based on the licensee's calculations for protecting PCS P-T limits under a design basis energy addition transient. The proposed TS 3.1.lh(3) would permit the first idle PCP starting when the secondary system temperature is less than 100*F above PCS cold leg temperature and PCS heatup or cooldown rate is less than or equal to 10*F/ hour. This proposed TS is supported by the licensee's analysis since at 10*F/ hour heatup or cooldown rate, the P-T limits is very close to the isothermal curve which was assumed in the analysis. The proposed TS 3.1.1h(4) would permit starting the first PCP when the secondary system temperature is less than 100*F above PCS cold leg temperature and pressurizer level is less than or equal to 57%.
The licensee stated that the 57% pressurizer level would indicate that there is a steam bubble in the pressurizer and the presence of the steam bubble in the pressurizer would provide protection against PCS P-T limits for a higher heatup and cooldown rate when the secondary system temperature is less than 100*F above PCS cold leg temperature.
In response to the staff's request for a justification of the above assertion, the licensee in its letter dated February 20, 1995, submitted a revised TS Figure 3-4 which reflects lower PORV setpoints than its originally proposed settings in its October 5, 1994, letter.
In addition, the licensae provided the results of its study regarding an energy addition transient due to startup of an idle PCP when the secondary system temperature is 100*F above the PCS temperature with a steam bubble in the pressurizer. The licensee stated that because the PORV stroke time is relatively short, it will reach full open before the PCS pressure exceeds 105%
of its setpoint. The volume of the steam bubble is more than enough to compensate for the expansion of primary coolant due to heatup by the secondary system fluid at a temperature which is 100*F higher than the PCS temperature.
The pressure rise will be stopped when the PORVs reach full open because the relief capacity of one single PORV exceeds the calculated PCS expansion rate.
The licensee has concluded that the results of its calculations confirm that with the revised TS Figure 3-4, the resultant peak pressure will remain below the transient pressure limit allowed by ASME Code Case N-514. We find the licensee's assessment acceptable.
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-The proposed TS 3.1.11 prevents PCP P-50A and P-50B.being operated-
' simultaneously when the PCS cold leg temperature. is less than 300*F. This is an added TS to minimize:the potential challenge to the allowable PCS P-T limit?
under low temperature operating conditions.
The licensee proposed changes in TS 3.1, 3.3, Figures 3-1, 3-2 and 3-4 reflect the changes discussed above. -:The staff has reviewed the licensee's submittals' and finds that the changes are based on applicable regulatory guidance in.
SRP 5.2.2 (Revision 2), are reasonably conservative and are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendment. The Michigan State official had no comments.-
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR
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Part 20.
The staff has determined that the amendment-involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is:no 'significant s
increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a' proposed finding that the amendment' involves no'significant hazards ' consideration and there has been no public comment on such finding (60 FR 501). Accordingly, the amendment meets the:
eligibility criteria for categorical exclusion set ferth in 10 CFR 51.22(c)(9).
5.0 CONCLUSION
The staff has concluded, based ~on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
B. Elliot C. Liang Date: March 2, 1995 l
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