ML17256A374
| ML17256A374 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 10/27/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17256A373 | List: |
| References | |
| NUDOCS 8211040217 | |
| Download: ML17256A374 (4) | |
Text
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UNITED STATES
~ NUTBAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 SAFETY EVALUATION REPORT PEAK CLAB TEMPERATURE REANALYSIS R.
E.
GINNA NUCLEAR POWER PLANT DOCKET NO. 50-244
1.0 INTRODUCTION
LER 81-22 (Reference
- 1) dated January 4, 1982 stated that the peak clad temperature (PCT) calculation has inadvertently assumed that only one of the four containment fan coolers was in operation following the limiting loss-of-coolant accident.
A reanalysis of the PCT was therefore required because a conservative analysis assumes that all post-accident heat re-moval. systems in containment operate at their maximum capacity.
As stated in SRP 6.2.1.5, "Minimum Containment Pressure Analysis for Emergency.
Core Cooling System Performance Capability Studies," the core flooding ra'te is governed by the capability of the ECCS water to displace the steam generated
. i'n the reactor vessel during the core reflooding period.
For PWR plants, there is a direct, dependence of core flooding rate on containment prFssure; i.e., the core flooding rate will decrease with decreasin'g containment pres-sure.
Therefore, by maximizing operation of'the post accident heat removal
'ystems, the containment pressure will be minimized.
This, in turn, will maximize the. time necessary to reflood the core and thus result in a maximum PCT.
On May 20, 1982 the licensee subIIitted a reanalysis of the PCT (Reference 2).
The reanalysis was performed by Exxon Nuclear Company (ENC) and assumes that all four of the containment fan coolers are in operation following the postulated accident.
2.0 EVALUATION The licensee has reanalyzed the most limiting large break (0.4 DECLG ) for nominal primary coolant system pressure and temperature conditions (2250 psia
,and 573.5'F).
The reanalysis assumed four, instead of one, containment fan coolers were in operation.
The Ginna plant is a two loop Westinghouse PWR with upper plenum injection (UPI).
The staff's review of the Exxon Interim ECCS Evaluation Model con-cluded that using ECCS models with conventional lower plenum injection may
'ot be a conservative approach for plants with UPI.
Therefore the staff Sal10eoal7 mZOaZ PDR ADOCK 05000244
.PDR developed a bounding interim m'odel for UPI that takes into account the affects of steam generation, steam condensation and liquid entrainment on. the core reflood rate and the associated change in PCT.
'The initial Exxon model. assuming lower plenum injection (and inadvertently assuming only one containment fan cozier,) calculated a
PCT of 1922 F.
Using the interim mode') modifications to account for UPI resulted in a reduction of the PCT to 1906'F.
The May 20, 1982 submittal included the revised PCT analysis using the ENC WREM-II A computer code (this code was approved by the staff in Reference
- 3. )
In the ENC LOCA ECCS analysis, the fan coolers begin to remove heat from the containment approximately 26 seconds after the postulated pipe break.
Since fan cooler operation begins after end of bypass time, reanalysis of the blowdown and hot channel calculations are not required.
The revisions to the PCT calculation necessitated by the increased fan cooler capacity are:
o'ontainment pressure response with appropriate blowdown mass and energy input using COMTEHPT-LT/22.
o Accumulator and safety injection system (SIS) response with appropriate containment pressure using RELAP4-EH/ENC28FC.
o Refill with appropriate accumulator arid SIS flows.
o Reflood with appropria'te containment
- presume, accumulator and SIS flows using REFLEX.
o fbt rod heatup with appropriate reflood rates using TOODEE2/
tQ Y79.
o Delta PCT with appropriate ref1ood rates to account for upper pl enum" injection.
'he key parameters in the PCT reanalysis are containment
- pressure, fan cooler activation time and the time at which the PCT occurs.
For this analysis the fan coolers are active for approximately 80 seconds before PCT occurs.
During this.time the 'containment backpressure has been re-duced by about 10% due to the factor of four increase in fan cooler capacity.
The revised limiting br'eak calculation using ENC WREN-IIA produced a
calculated PCT of 1938'F.
Using the interim UPI model previously dis-
~
cussed resulted in a PCT of,1 928'F.
These calculations were performed
't a
peak iinear heat generation ra:e of 14.03 kw/ft (p
= 2.32) for ENC fuel (102% of 13.76 kw/ft).
- 3. 0 COH CLUSI OH The limiting peak clad temperature analysis for the Ginna= plant had to be reanalyzed when it was realized that the existing analysis was non-conservative.
This was because the post accident containment heat removal systems were not assumed to be operating at their maximum capacity.
The revised calculations used methods that have previously been found acceptable by 'the staff.
The peak clad temperature of 1928'F is below the limit of 2200'F found in 10.CFR 50.46, Based on our review of the
'icensee's submittal we find the reanalysis of the peak clad temperature to be acceptable.
4.0 REFEREHCES 1.
LER 81-22 for Ginna.
Transmitted from Rochester Gas and Electric Corporation to NRC (John E. Maier to Ronald C.
Haynes) dated
~
January 4, 1982.
2.
Letter from Rochester Gas and Electric Corporation to NRC (John E.
Maier to Dennis M. Crutchfield) dated May 20, 1982.
3..
Letter.from NRC to Exxon Nuclear Company (T. Ippolito to W. Necggdom),
'ER for EHC WREM-IIA Evaluation Model dated Harch 30, 1979.
5;0.
ACKNOllLEDGEMENTS This Safety Evaluation Report was prepared by D. Pickett.
Da'te:
October 27, 1982
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