ML20082V262
| ML20082V262 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/05/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082V247 | List: |
| References | |
| NUDOCS 9109230185 | |
| Download: ML20082V262 (12) | |
Text
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UNITED STATES l 1r /gf ;1
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...p SAFETY EVALUATION BY THE OfflCE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 65 TO FACILITY OffRATING LICENSE NO. DPR-80 AND AMENDMENT NO. 64 TO FAClllTY OPER,LTING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT. UNIT NOS,1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By letter dated December 21, 1990, Pacific Gas and Electric Company (PG&E cr the licensee) requested amendments to facility Operating License DPR-80 and DPR-82 for Diablo Canyon Units 1 and 2, respectively.
The amendment application is des'.,aated License Amendment Request LAR-90-13 (Reference 1).
The amendments change the combined Diablo Canyon technical specifications (TS) by modifying the fin. rates for the-centrifugal charging pumps (CCPs) and the safety injection (51) pumps.
Also, the value of the max :num containment d
design pressure is rounded up to a whole number.
During the course of its review of the amendment application the staff obtained clarifying information from the licensc 3 by telephone (Reference 2).
This information did not alter the proposed action or affect the initial determination notice ( in the federal R_egister on January 23, 1991.
The surpose of these amen @ents is to:
(1) allow operation of the subsystms of t1e emergency core cooling system (ECCS) associated with the CCPs with the recirculation (miniflow) lines open during the injection phase of ECCS operation, (2) provide additianal margin between the minimum and maximum CLP and 51 pump ficw requirements, and (3) provide a surveillance requirement for the difference between minimum and maximum irdividual line flows (flow imbalance) for both the CCP lines and SI pump lines.
The revised flow rates provide a broader range between minimum and maximum flow rates which allows explicit inclusion af the orifice uncertainties associated with flow measurement in the TS.
These changes also facilitate adjustment of the flow balance vuh es and performance of the associated surveillance test proceduro.
Specifically, these amendments modify TS 3/4.5.2, "ECCS Subsystems - T greater than or equal to 350'F," by revising values for minimum and maximum centrifugal charging and safety injection flow rates anc revised values for injection line flow imbalance for operation of Unit 1 in Cycle 6 and Unit 2 in Cycle 5 and for the succeeding cycles. The TS changes are as follows:
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91o923o10s 91o90s PDR ADOCK 05000275 P
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2 (1) Minimum Flow - 3 Loops Surveillance requirements ior the sum of the injection line flow rates, excluding the highest flow rate, is reduced from 346 gpm to 299 gpm for the centrifugal charging the safety injection (SI) pumps (CCPs), and from 463 gpm to 427 gpm for psnp s.
(2) Maximum Pump Flow l
lwo surveillance requirewnts are renumbered and the total pump flow rate requirements is increased from 550 gpm to 560 gpm for the CCPs, and f rom 650 gpm to 675 gpm for the 51 pumps.
(3) Flow - Sum of 4 Loops New surveillance requirements are added to require the total flow rate through all four injection lines to be less than or equal to 461 gpm for the CCPs 6nd 650 gpm for the Si pumps.
(4) Maximum Unbalance New surveillance requirements are added to require the difference between the maximum and minimum individual injection line flow rates to be less than or equal to 15.5 gpm for the injectien-lines associated with the CCDs and 20.0 gpm for the injection lines associated with the Si pumps.
The associated TS Bases are also appropriately revised.
2.0 BtCKGROUND TS 4.5.2.h identifies surveillance requiremnts for flow rates for the portions of the ECCS associated with the CCPs and SI pumps.
The purpose of these surveillance requirements is to verify that the plant conf'guration is consistent with the assumptions used in the design, the values in the Final Safety Analysis Report (FSAR),(and calculation of the pump operability limits and net positive suction head NPSH) requirements.
Verification is made by masuring flows using the pressure drop across flow orifices.
Previously, the liccnsee did not include orifice uncertainties when comparing the flow test results to the TS 4.5.2.h limits.
These amendments allow the measurement uncertainties associated with the flow orifices to be explicitly included in the TS, and broaden the range between mininni and maximum flow limits.
Diablo Canyon Unit 2 Licensee Event Report (LER) 2-85-030-1, "ECCS Safety injection System Flow Balance Test," dated October 1,1989, described how the previous TS limits on minimum and maximum flow provided a narrow band within which the flows must be adjusted.
The narrow band makes the flow balancing difficult, which may result in running the pumps for an unnecessarily long period of time while balancing flows.
The narrow band also provides little margin to accommodate minor system performance changes.
The current emergency
3 operating procedures (EOPs) direct the operator to close the CCP miniflow valves during the injection phase of ECCS operation in the event the ECCS is actuated and the reactor coolant system (RCS) pressure is reduced.
This is because the design and safety analysis ECCS flows were calculated assuming zero miniflow.
These amendments delete this requitvment.
The licensee has perfonned calculations of ECCS flows to support the CCP miniflow valves being open and remaining open during injection.
15 4.5.2.h previously had no limits for flow unbalance between individual injection lines.
Injection line flows were adjusted during the flow balance test to minimize flow inbalance between lines.
The revised TS 4.5.2.h specifies an allowed maximum flow imbalance between injection lines.
The licensee has supported this change with a safety evaluation.
Specifically, the licensee examined all the required safety analyses that could be affected by the changes in ECCS flows. These were determined to be:
(* ) Loss of Coolant Accident (LOCA)
This includes (a) the large break LOCA, (b) the small break LOCA, (c) blowdown reactor vessel and loop forces, (d) post LOCA long term cooling, and (e) containtnent integrity.
(2) Steam Generator Tube Rupture (SGTR)
This includes the overfill case.
(3) Rupture of the Main Steam Line This includes (a) core responseenergy release outside of contalnm(b) containment ent, and (d) accidental depressurization of the main steam line system.
(4) Major Rupture of a Main feedwater Line (5) Spurious Actuation of the Safety injection System at Power (6) Low Tenperature Overpressure System In addition, the effects of the flow changes on pump operability were examined. These effects included:
(a) adequate NpSH available for the increased flows (b) required motor horsepower.
The licensee stated that its safety evaluation of these proposed changes shows acceptable ECCS performance with respect to the analyses in the FSAR update.
Our evaluation of these changes are given in Section 3.0 of this safety evaluation. The licensee states that the benefits of these amendments include enhanced plant operation, enhanced performance of the surveillance test, and a reduction in the possibility of violating the TS due to a narrow band for allowable operation.
Similar requests have been made by other utilities and approved by NRC, e.g., the D.C. Cook and Trojan plants.
~
4 3.0 EVALVATION in support of these amendnents the licensee submitted safety evaluations in which the ECCS flows assured in the safety analyses and the pump operability limits and NPSH requirements were calculated by modeling the pumps, valves, and piping of the ECCS system.
Some safety analyses are limited by the minimum ECCS flow to the RCS and some analyses are limited by the maximum ECCS flow to the RCS.
The FSAR Update-certified performance curves plus 2 percent were used for the maximum pump performance curves, and the FSAR Update minimum pump performance curves were used as the minimum performance curves.
The pump operability and NPSH calculations are limited by the maximum flow through the pump.
The window between minimum and maximum total injection tlows was broadened to include orifice uncertainties and to allow a larger target band for balancing.
This resulted in increasing the maximum safety analysis flow and decreasing the minimum safety analysis flows.
The essumption that the CCP miniflow line will remain open had the effect of reducing both minimum and maximum safety analysis flows.
The conbination of these two changes has the net effect of reducing the minimum ECCS flows assumed in the analyses.
The net effect on the maximum ECCS flows varies; for some analyses the maximum ECCS flow is decreased and for others the maximum ECCS flow is increased.
The impact of these changes is evaluated below.
3.1 Loss of Coolant Accident (LOCA)
Minimum ECCS flows consistent with revised TS 4.5.2.h are limiting for the LOCA analysis of core cooling.
The balancing of the flow in the individual injection lines to the four loops is not a concern for the analysis of a large breal LOCA as the entire RCS depressurizes to nearly containment pressure and the back pressure for all injection lines is essentially the same.
- However, injection line balancing is a concern for small break LOCA where balancing of the injection flows from the SI pumps and CCPs is necessary to ensure that adequate flow goes to the RCS rather than spilling out the break.
The large break LOCA and small break LOCA are evaluated below.
3.1.1 Laroe Break LOCA The large break LOCA analysis of record for Diablo Canyon is described in the current FSAR Update, and is a double-ended cold leg guillotine break with a discharge coefficient of 0.4.
This analysis was performed using the NRC-approved 1981 ECCS evaluation model with the BASH code, and resulted in a peak cladding temperature (PCT) of 2158'F. This result includes a 50'F
. transition core penalty for the transition to VANTAGE-5 fuel.
The licensee states in Reference 1 that since the ECCS analysis of record was perforned, but before inclusion of the changes authorized by these amendments, i
other changes have been made which are estimated to increase the Diablo Canyon PCT, including penalties for ECCS evaluation model changes and previous safety evaluations, to a value of 2188.2'F. Thus, the cumulative effect on PCT of all changes made since the ECCS analysis of record was performed was 30.2'F before issuance of these amendments.
L
. The ECCS flow rates modeled for the large break LOCA include minimum flow rates from one CCP, one 51 and one RHR purrp.
for conservatism, the containment pressure was previously assumed to be 0.0 psig, which maximizes the spillage and minimizes flow to the RCS.
With 0.0 psig containment pressure, the changes allowed by these anendnents result in a decrease in the calculated minimum ECCS flow of 114 gpm for the pressure range of interest.
The NRC staff estimates that this change alone would result in a PCT increase of greater than 20*f.
However as the licensee notes that at the time the PCT is computed to occur, the co' ulated containment pressure is above 17 psig.
The licensee states that r revised ECCS analysis using the containrent pressure of 17 psig would show that the spillage is reduced and a minimum of 145 gpm of additional safety injection flow would bt delivered to the RCS.
This would result in a decrease in PCT which is conservatively estimated to cancel out the PCT increase resulting from the 114 gpm safety injection flow decrease discussed above.
On this basis the licensee states that the revised minimum ECCS flow rate requirenents will not adversely affect the large break LOCA analysis, PCT will not be increased, and the current ECCS analysis results will remain valid.
The staff has reviewed the licensee's conclusion and finds it to be acceptable.
However, the staf f concludes that the changes authorized by these amendments, in cortination with the changes previously nade since the ECCS analysis of record was performed, result in a change in PCT which is significant per the 10 CFR 50.40 definition.
Specifically,10 CFR 50.46 defines a significant change to be a cumulation of changes and errors such that the sum of the absolute nagnitudes of the changes is greater than 50*f.
The staff concludes that these amendrents result in such a cumulation, and therefore the licensee is required by 10 CFR 50.46 to perform a new large break LOCA analysis and to propose a schedule for this reanalysis within 30 ays of the issuance of these amendments.
3.1.2 Small Break LOCA The current small break LOCA analysis uses tne tb -approved small break LOCA ECCS evaluation model with the NOTRUMP code.
Fo'e a 4-inch equivalent diameter break the most limiting PCT, including penalties for previous ECCS evaluation i
model changes and safety evaluations is 1077.7*f and 1760.7 F for Dieblo Canyon Units 1 and 2 respectively.
In Reference 1 the licensee states that the small breat LOCA will incur a PCT penalty of 58'F due to the revised minimum CCP and SI pump flows since the integrated ECCS flow will be lower than was assumed in the small break analysis.
This 58' PCT penalty includes the ef f ects of changing the containment back pressure f rom the previous conservative assumption of 0.0 psig to a more realistic value.
See the discussion of this in Section 3.1.1, above.
Therefore, these amendments will result in PCT values of 1735.7 F and 1818.7 F for Units 1 and 2, respectively.
These values are below the 2200*F limit value.
Therefore, the conclusions presented in the fSAR Update for small break LOCA remain valid and cemonstrate that small break LOCAs continue to be non-limiting after this change.
However, the staff concludes that the changes authorized by these amendments result in a change in PCT A ich is significant per the 10 CFR 50.46 definition. Specifically,10 CFR 50.46 defines a significant change to be one which results in a calculated PCT different by more than 50'f from the PCT calculated for the limiting transient using the last acceptable model. T he staff concludes that these amendments result in such a change, and therefore the licensee is required by 10 CFR 50.46 to perform a new smil break LOCA analysis and to propose a schedule f or this reanalysis within 30 days of the issuance of these anendments.
3.1.3 Blowdown Re:St,or Vessel and Loop f orces The blowdown hydraulic loads resulting from a LOCA are covered in Section 3.9.3.5 of the fSAR Update. The maximum loads are generated within the first few seconds af ter breat initiation. This is well befure ECCS flow is calculated to occur. Therefore, the revised CCP and 51 pump flow requirements will not affect the results of the LOCA hydraulic forces calculation.
3.1.4 Post LOCA Long Term Cooling The ECCS is also required f or recirculation during recovery f rom a LOCA for long term core cooling where the ECCS draws water from . containment sump.
The effects of the revised ECCS flow requirerents Lo long term core cooling are discussed below for the:
(1) subtriticality requirement, (2) hot leg switchover to prevent boron precipitation, and (3) minimum flow rwquirement.
3.1. 4.1 Subtriticality Requirement This requirenent is to ensure that the reactor remains subtritical with the control rods out by use of barated ECCS water. The licensee has detennined that the revised ECCS flow rates would have no effett on the boron concentrations and volunes assuned for the calculation.
Therefore, the subcriticality requirement will be net with the revised ECCS performance requirements.
3.1.4.2 Hot leg Switchover to Prevent Potential Boron Precipitation Ouring recirculation, turated riter i.c injected into the RCS alternately f rom the cold legs and the hot legs to prevent boron from coming out of solution and plating out on the fuel rods.
The licensee has determined that the revised ECCS flow rates would have no effect on the power level, or volures assumed for the RCS, refueling water storage tant (RWST) and accumulators, and would have no effect on the boron concentrations.
Therefore there is no effect on the post-LOCA hot leg switchover tine.
3.1.4.3 Minimun Flow Requirement As the basis for the minimum flow rate, a calculation is made for the hot leg injection mode in accordance with the reg'Jirements of 10 CfR 50.46 for long term cooling.
The licensee stated that this calculation of the required flow
..i 7
rate is based on the boil off rate. This boil-off rate is increased by a factor of 50%.
Because of only a small reduction in the minimum ECCS flow and the 50% factor, the resulting minimum ECCS flow rate will not violate the long term cooling requirement.
3.2 Steam Generator Tube Rupture (SGTR)
The ECCS flow maintains RCS inventory while the RCS is being depressurized following a SGTR.
However, since ECCS flow is at higher pressure than the ruptured steam generator (SG) pressure, the ECCS flow must be terminated to stop break flow and recover from a SGTR. Maximum ECCS flows are assuned in the analysis to predict conservative values and are consistent with the proposed Surveillance Requi vments in TS 4.5.2.h.(1)(b) and (2)(b).
Flow calancing is not a concern for SGTR since all lines are subject to RCS pre 5sure which is essentially equal in all four loops.
The FSAR Update SGTR analysis assumea the primary to secondary break flow to be terminated at 30 minutes af ter initiation _ of the SGTR event.
The SGTR analysis methudology was developed by the SGTR Subgrou s of the Westinghmse Owners Group.
In a revised SGTR analysis (Reference 3) the licensee used tne NRC approved SGTR analysis methodology presented in WCAP-10698 and supplement 1 to WCAP-10698. The LOFTTR2 program was used to model the operator actions during recovery f rom a SGTR event. The anal to SG overfill, and (yses included (1) an overfill case to demonstrate margin
- 2) an offsite case to demonstrate that offsite radiological consequences are acceptable. These cases are discussed below.
3.2.1 Overfill Case The revised maximum ECC5 flow for the margin to overfill case is increased over the values used in the analysis and is therefore less conservative.
Therefore, the primary to secondary break flow rate would be increased and the steam release rate from the ruptured SG would be reduced with the revised maximum ECCS flows.
Thus the margin to overfill would be adversely affected.
Based on a sensitivity study of ruptured SG water volune to ECCS flow, the licensee estimated that the margin to overfill would decrease by approximately 25 cubic feet with the revised maxinum ECCS flows.
However, the available margin is greater than this. Therefore it was concluded that if the event were rehalyzed considering the increased maximum ECCS flows, acceptable results would be obtained. The staff agrees with this conclusion and finds it acceptable.
3.2.2 Offsite Dose Case Since the revised maximum ECCS flow is lower than the ECCS flows assuned in -
the analysis for offsite doso, the revised maximum ECCS flow would have no adverse effect on the offsite dose. Therefore we find the revision to be acceptable as the FSAR Update results are bounding.
8 3.3 Rupture of Main S_ team Line for a Steam Line Break (SLB) the ECCS provides borated water which offsets the reduction of shutdown margin resulting from moderator cool down.
The analysis of a SLB assumes minimm ECCS flows. The minimum flows calculated for the safety evaluation were consistent with the proposed minimum flow Surveillance Requirementi in TS 4.5.2.h.(1)(a) and (2)(a). Flow balancing is not a concern for SLB since all lines inject to RCS pressure which is essentially the same in all four loops. The staff finds that the revised ECCS flows are acceptable for the SLB as tne revised flows are consistent with the calculations u:ed in the safety evaluation whhh indicated an insignificant effect on the return to power.
3.3.1 Core Response The ECCS delivers borated water to the core to provide negative reactivity in order to limit the return to power.
Section 15.4.2.1 of the FSAR Update oemonstrates core integrity in the event of a SLB by verifying that the Departure frum Nucleate Boillng (DNB) design basis is met.
The licensee stated that 5 sensitivity bnalysis was performed that confirmed that the reduction in minimum ECCS flow would have a negligible effect on the calculated core heat flux (return to power).
At the time of peak heat flux, which corresponds to the time of minimum DNBR, the core thermal hydraulic conditions would be essentially unchanged.
Therefore the DNB design basis would be met and the conclusions of the FSAR Upde.e would remain valid.
The staff finds this to be acceptable.
3.3.2 Mass and Energy Release Inside Contairimeg The mass and energy release inside containment are calculated to ensure that the containment pressure and temperature do not exceed acceptable levels.
The design pressure is 47 psig.
A temperature response transient is used to demonstrate that the safety-related temperature instrumentation will be in compliance with IEEE requirements.
As discussed above for core response to SLD, the reduced minimum ECCS flow would have an insignificant effect on the return to power.
Therefore the releases are limited mainly by the characteristics of the break and secondary side steam generator conditions.
Sensitivity analyses were made that confirmed that the reduction in minimum ECCS flow would have insignificant ef fects on the calculated mss and energy releases.
Therefore, the calculated contairment response would be unaf fected and the conclusions of the FSAR Update remain valid.
3.3.3 Mass and Energy Release Outside Containment As discussed above for core response to SLB, the reduced ECCS flow would have an insignificant effect on the return to power.
Sensitivity studies confirmed that a reduction in ECCS flow does not significantly impact the calculated mass releases.
Therefore, the mass and energy release outside of containment remains applicable and the conclusions of the FSAR Update remain valid.
c.. e i
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3.4 Major Rupture of a Main Feedwater Line The feedwater line rupture transient analysis assumes the actuation of one CCP to provide ECCS flow following a low steam line pressure safety injection signal. The primary RCS heat removal is provided by the auxiliary feedwater flow with the ECCS flow providing an additional heat sink to remove decay heat.
The licensee stated that the feedwater line rupture analysis takes credit for steam line check valves to prevent reverse flow and to limit the cooldown from the secondary side break in the faulted SG.
Therefore the RCS pressure remains high during the transient.
The flow f rom the CCP is a relatively unimportant source of heat removal. Therefore the reduced ECCS fluw rate requirement does not have a significant effect on the feedwater rupture transient and the conclusions of the FSAR Update remain valid.
3.5 Spurious Actuation of the Safety injection System at Power The analysis of the inadvertent operation of the ECCS during power operation i
is to show that the core integrity is maintained by verifying that the DNB design basis is met. The licensee stated that this event is non-limiting with respect to DNB as the addition of borated water to the RCS serves to greatly reduce core power and increase the margin to DNB.
The revised maximum ECCS flows based on the proposed surveillance requirements are less than the flows assumed in the analysis and would not adversely impact the analysis.
Therefore the conclubion is in the FSAR Update remain valid.
3.6 Low Temperature Overpressure System The low temperature overpressure system (LTOPS) provides RCS overpressure protection during startup and shutdown. The CCPs discharge into the RCS through the normal charging lines and are used during a charging / letdown mismatch transient. The proposed changes to the surveillance requirements are only for the flows from the CCP associated with the ECCS. Therefore the normal charging flows are not affected and there is no impact on flows modeled in the LTOPS analysis or LTOPS initiation setpoint. Also, the operational change of leaving the miniflow lines open does not adversely affect the LTOPS analysis because the current analysis assumes that the miniflow lines are closed which results in more flow to the RCS. Therefore the current analysis is bounding for cperation with the miniflow lines open.
3.7 Pump Operability For the CCP and SI pumps the two main concerns for pump (operability related to the increase _in pump runout operation conditions are:
- 1) cavitation, and (2) horsepower capability.
Cavitation will occur if the NPSH required by the
_ pumps is not satisfied by the available NPSH at the increased runout flow l
rates. Also, the pump motors must be capable for operating satisfactorily at the increased runout flow ra' which could require increased horsepower, l
These concerns are discussed
>w.
u __ _._. _ _,_ _ - _ _.___. _._.. _. _ _ _ _ _
..t 10 3.7.1 Centrifuy l Charging Pump (CCP)_
The licensee reported that the calculated NPSH available for the CCP at $60 gpn,was 44 feet, whereas the NPSH required is 24 feet.
Therefore the NPSH available is ample.
Regarding *he horsepower, the licensee reported that the CCP falling head curve results in a brake horsepower curve that is flat at rates beyond 550 gpm.
There%re, the horsepower requiremnts for 560 gpm are not increased and are withir the capability of the notor.
3.7.2 Safety injection (51) Pump The licensee reported that the calculated NPSH available for the $1 pumps at 675 gpm is 31 feet whereas the NPSH required is 29 feet.
Therefore the NPSH available is satisf actory.
Regarding horsepower, the licent.ee reported that the 51 pump f alling head curve results in a brake horsepower curve is flat at rates beyond 650 gpm.
Therefore, the horsepowers requirements for 675 gpm are within ti,e capability of the motor.
4.0 EVALUATION OF TECHNICAL. SPECIFICA110NS As a result of the changes requested to modify the CCp and SI pump flow rates, the following changes to the Technical Specifications were proposed.
1.
Page 3/4 5 TS 3/4.5.2, "ECCS subsystems - T greater than or equal to 350*F."
OV9 The following changes to Surveillance Requirement 4.5.2.h were proposed:
a.
Surveillance Requirements 4.5.2.h(1)(a) and (2)(a) - The sum of the injection ficw line flow rates, excluding the highest flow rate, was reduced from 346 gpm to 299 gpm for the CCPs and f rom 463 gpm to 427 gpm for the $1 pumps.
b.
Two surveillance Requirements 4.5.2.h(1)(b) and (2)(b) were renumbered to 4.5.2.h(1)(d) and (2)(d), and the total pur@ flow rate requirements were increased from 550 gpm to 560 gpm for the CCes, and from 650 gpm to 675 gpm for the SI pumps, c.
New Surveillance Requirements 4.5.2.h(1)(b) and (2)(b) were adoes to require the total flow rate through all four injection lines to be less than or equal to 461 gpm for the CCPs and 650 gpm for the 51 pumps.
d-New Surveillance Requirenents 4.5.2.h(1)(c) and (2)(c) were added to i
require the difference between the maximum and individual injection line flow rates to be less than or equal to 15.E gpm for the L
injection lines associated with the CCPs and 20.0 gpm for the l
injection lines associated with the SI pumps.
l l
The above TS changes were found to be consistent with applicable requireneni and acceptable as discussed above in Section 3.0.
,e
, 2.
Page B 3/4 6-2 Bases section B 3/4.5.2, "ECCS Subsystems," includes background information on the Surveillance Requirements for mininum flow maximum flow, maximum difference between the minimum and maximum individual injection line flows, and the maximum total pump flows to ensure that the runcut Ilmits of the CCP and $1 pumps are met. We find these to be acceptable as discussed above in Section 3.0 of this safety evaluation.
3.
Page B 3/4 6-1 Bases section B 3/4.6.1.4, " Internal Pressure," was nodified to change the maximum peat prest /re expected to be obtained from a LOCA event from "less than 46.65 p$ig" to "less than 47 psig." We find this acceptabic because it is a small change obtained by rounding up the value of the i
previous value given.
4.
Page B 3/4 6-2_
Bases section B 3/4.6.1.6 " Containment Structural Integrity," was modified to delete "of 46.'65 psig" f rom the sentence " Structural integrity is required to ensure that the containment will withstand the maximum pressure of 46.65 psig in the event of a LOCA." We find this acceptable because the maximum pressure was previously defined and therefore use of the value here is redundant.
In summary, the NRC staff has reviewed the licensee's basis for the proposed changes to the Combined Technical Specifications for Diablo Canyon Units 1 and 2 and finds them acceptable.
5.0 STATE C0jiSULTATION In accordance with the Commission's regulations, the California State of ficial was notified of the proposed issuance of these cmendments.
The State official had no conments.
6.0 ENVIRONMENTAL CONSIDEPATION These amendments involve changes with respect to the installation or use of a facility component located within the restricted area as defir:ed in 10 CFR Part 20 or changes in surveillance requirements.
The staff has determined that the amendments involve no significant increase in the amounts, and no tsignificant chaage in the types, of any effluents that may be released offsite and what there is no significant increase in individual or cumulative occupational radi uion exposare. The Comission has previously issued a proposed 'inding that the amendments iuolve no significant hazards censi%retion and there has been no public comment on such finding (56 FP 0552). Accorfir';1y, these amendments meet the eligibility criteria for categorical exclusion set furth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
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,,,'t 7.0 CONrL'uSION The NRC staff has eva5ated the proposed changes and their impact on the FSAR Chapter 15 accidents. Specifically considered was the proposed modification of the values for minimum and maximum centrifugal charging and satety injection pump flow cates and revising the values for injection line flow imbalance. The staff finds that (1) the conclusions currently included in the FSAR remain valid and (2) the proposed TS changes are acceptabic, as described in Section 4.0 of this safety evaluation.
However, because the changes authorized by these amendments result in changes in peak cladding temperature that are significcnt (as defined in 10 CFR 50.46), the licensee is required by 10 CFR 50.46 to submit within 30 days of the 6tte of issuance of these amendments a proposed schedule for providing a reenalysis or taking other action as may be needed to show compliance with the requirements of 10 CFR 50.46.
The NRC staff has concluded, based on the considerations discussed above, that I
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) ch activities will be conducted in compibnce with the Commission's r %,. cions, and the issuance of these amend.nents will not be inimical to the common defense and security or to the health and safety of the public.
8.0 REFERENCES
1.
Letter No. DCL-90-297 from J. D. Shiffer, PG&E, to USNRC, "Diablo Canyon Units 1 and 2 License Amendment Request 90-13," dated December 21, 1990.
2.
Telephone conversation between Roger Johnson, PG&E, and Harry Balukjian, USNRC, on May 9, 1991.
3.
Letter No. DCL-88-114 f rom J. D. Shlffer, PG&E, to USNRC, " Revised Steam Generator Tube Rupture (SGTR) Analysis for Diablo Canyon Units 1 and 2,"
dated Apr il 29, 1988.
Principal Contributors:
H. Balukjicn H. Rood Dated: September 5, 1991 3
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