ML20215C434
| ML20215C434 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/12/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20215C413 | List: |
| References | |
| TAC-65011, TAC-65012, NUDOCS 8706180117 | |
| Download: ML20215C434 (6) | |
Text
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NUCLEAR REGULATORY COMMISSION py WASHINGTON, D. C. 20555 4
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m SAFETY EVALUATIOM 8Y THE OFFICE OF NUCLEAR REACTOR REGULATION t
RELATED TO AMEND' MENT NO.14 TO FACILITY OPERATING LICbSE NO. OPR-80 y
~ AND AMENDMENT NO.13 TO fat'ILITY OPERATING LICENSE NO. DPR-82 r
PACIFICGAS'AjiDELECTRICCOMPANY GIk3LO CANYON NUCLEAR PMIER PLANT, UNIT NOS.1 AND 2 L <-
DOCKET N05. 50-275 AND 50-323
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1.0' INTRODUCTION N
. By le' ter ciated March 25, 1987, as supplemented May 26, 1987 Paciffir
~ Gas aad Electric Company (PA&E or:the licensee) requested amendments to the Technical Specifications appendr.d to-F6c111ty Operating License Nose
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DPR-80 and DPR-82 for the Diablo Canyon Nuclear Power Plant,1 Unit.Nos. 1 and 2o The proposed amendments would revise the.Diablo Canyon combined-Technical Specifications for Units 1 and 2 to accommodate Cycle 2 and
'1 later operation of Unit 2, and Cycle 3 and later operation.of Unit 1.
The requested amendment is in the form of proposed changes to the Technical Specifications.as follows:
1.
Increase the F partial power multiplier.
2.
Increase the refueling water storage tank and accumulator boron concentration.
3.
Relax the third 1ine segment of the K(z) figure.
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I; 2.0 EVALUATION
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1.
F Multiplier f'
The Technical Specifications for Westinghcuse reactors historically have allowed for an increase in F with decreasing power level to compensate for power distributioc changes with control rod insertion and decreasing reactivity feedback.
This has been done with a 0.2 part power multiplier on F The 0.2 multiplier on occasion has been restrictive at low power, and in recent years a 0.3 multiplier has been approved for a number of operating plants.
In general the restriction that the average enthalpy at the vessel exit be l
less than the enthalpy of saturated liquid is more limiting tha'n DNB considerations, so the increase in the allowable F at reduced power levels does not result in large changes to the reactor safety limits defined in Technical Specification Section 2.
The exit enthalpy
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restriction is not impacted by the radial peaking factor.
The licensee
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presented an analysis supporting this.
The analysis for Diablo Canyon Units 1 and 2 showed that elight i
modification of the reactor cero safety limit curve, TS Figure 2.1-1b, was required as a result of the change in the F multiplier.
The licensee proposed a revised TS Figure 2.1-1(b) reflecting these changes.
(The figure provided in the licensee's March 25, 1987 submittal contains an error which has been corrected in a submittal dated May 26, 1987.)
As a consequence of the change to the safety limits, the licensee there-fore also proposed changes to tne equation constants for the over-temperature AT trip setpoints.
Rean61ysis of affected non-LOCA accident events with the revised setpoints was performed and the conclusions for the non-LOCA accidents were found to remain valid as presented in the revised Diaolo Canyon FSAR.
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Because the proposed changes-(with the corrected Fig 2.1-1b) and the
- 1 accident evaluation are the result of. analyses using the methods described i
in the approved report WCAP-9272-P-A, "Westingh'ouse. Reload Safety Evaluation Methodology'.', we find them acceptable.
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. Boron Concentration 2.
The proposed license amendment request increases the Refueling Water Storage Tank (RWST) and accuraulator boron concentration.
These changes are required to have enough boron concentration to maintain the core subcritical following a large break'LOCA.
For Cycle l'on both units and Cycle 2 on Unit 1, the present minimum boron concentrations of 2000 ppm for the RWST and 1900 ppm for the accumulators are capable of maintaining the core subcritical.
For Unit 2, Cycle 2 the-reload safety evaluation I
determined that, with the excess reactivity provided for a longer cycle, i
if the burnup of Cycle 1 was less than 15,250 MWD /MTU, higher boron concentration in the RWST and accumulator were needed to satisfy.the post S'nce the Cycle 1 burnup was less than i
LOCA subcriticality requirement.
the stated value, the licensee proposes'to increase the boron d
concentrations for the RWST from between 2000 ppm and 2200 ppm to between 2300 ppm and 2500 ppm. The accumulator boron concentration is proposed to i
be increased from between 1900 ppm and 2200 ppm to between 2200 ppm and We examined the proposed changes to Technical Specifications 2500 ppm.
3.1.2.5, 3.1.2.6, 3.5.1 and Bases 3/4.1.2, 3/4.5.5 and 3/4.6.2.2 and find they correctly implemented these changes.
The proposed increased boron concentrations will also support future core designs with longer fuel cycles and higher burnup.
The licensee's submittal presented the results of analyses of the proposed increases in RWST and accumulator boron concentrations on the following areas of the Diablo Canyon Units 1 and 2 design:
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- Non-LOCA Transient Analysis 2.
LOCA Analysis a.
.Small Breaks b.
Large Breaks' c.
Long-Term Core Cooling.
d.
Boron ~ Precipitation 1
3.
LOCA Related Design Considerations i
a.
Radiological Consequences b.
' Hydrogen Production c.
Equipment Qualifications.
The non-LOCA safety. analyses. in which boron from the RWST or accumulators q
is involved are uncontrolled boron dilution, accidental'depressurization~
of the main ~ steam system, spurious operation of the safety injection
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.n at power, minor secondary system pipe breaks, rupture of a main steam line, end rupture of.a control rod drive mechanism housing.
The analyses'show no negative-effect of the proposed boron concentration increases'on the'non-LOCA' transients.
The proposed boron concentration changes do not have any effect on the l
sms11 or large break LOCA analyses except for the long term cooling post LOCA shutdown analyses.
For these analyses, the increased concentrations are required for Unit 2 Cycle 2 as discussed above.
For future cycles of both units, confirmation that the proposed increases in boron concentration will provide enough margin to keep the core subcritical for long term cooling requirements is required.
This will be accomplished through the normal cycle-specific reload safety evaluation process.
i The analyses of boron precipitation and other LOCA related design considerations all showed acceptable results.
We therefore conclude the proposed RWST and accumulator boron concentration increases are acceptable.
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3.
K(z) Third Line Segment
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i The K(z) curve provides the normalized heat flux hot channel factor asia function of core height.
Near the top of the core, from 10.8 to 12.0 ft.,
l the present K(z) curve decreases rapidly from 0.94 to 0.43.
A LOCA reanalysis was. performed by Westinghouse using a K(z) curve which continues'the'seco'nd Tine segment as a straight line.
This eliminates the
' third line segment and causes 12 foot intercept of the K(z) curve to be i
0.924.
The third line segment of the K(z) curve is determined by the I
small break LOCA analysis.
Westinghouse reanalyzed the small break LOCA using the approved NOTRUMP code (WCAP-10054-P-A).
The three, four and six inch diameter break sizes were analyzed for Unit 2, as well as the limiting of these three break sizes for Unit 1.
The worst case was the four inch diameter break size.
This resulted in a peak cladding temperature of 1288 F for Unit 2 and 1244 F for Unit 1.
These results are well belov 'he peak cladding temperature limit of 2200 F specified in 10 CFR 50.
The proposed modification of the K(z) curve is there-fore acceptable for both units.
As discussed above, the Technical Specification changes proposed by PG&E in its letter'of March 25, 1987, and as modified in a letter dated May 26, 1987 are acceptable.
As requested in the March 25, 1987 letter, the changes should become effective immediately upon issuance of this license amendment for Unit 2 and by the completion of the second refueling outage for Unit 1.
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3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve changes in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
We have determined that the amendments involve no significant increase in f
the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission
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' has previouslyLissued'a[ proposed, finding that.the. amendments involve no l
significant' hazards' consideration and there has been no public comment on such finding; Accordingly, these amendments meets the eligibility.
^ criteria for _ categorical ' exclusion' set' forth in.10 CFR 51.22(c)(9).
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' Pursuant' to 10 CFR 51.22(b),.no. environmental' impact' statement or environ-l mental assessment'need be_ prepared in connection with the issuance of-1 these amendments.
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'4.d-CONCLUSION i
We have. 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, and (2) such activities will be conducted in compliance with~the Commission's regulations' and (3) the issuance of thenc amendments will not be inimical to the' common defense and security or tolthe health and safety of the public.
J Principal _ Contributor:
M. Duneniuld l
Dated:
JuneJ12, 1987 i
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