ML17320A966
| ML17320A966 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 03/28/1984 |
| From: | Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AEP:NRC:0860C, AEP:NRC:860C, NUDOCS 8404030385 | |
| Download: ML17320A966 (6) | |
Text
INDIANA8 MICHIGAN ELECTRIC COMPANY P.O. BOX 16631 COLUMBUS, OHIO 43216 ig.>l March 28, 1984 AEP:NRC:0860C Donald C. Cook Nuclear Plant Unit No.
2 Docket No. 50-316 L'icense 'No. lDPR-'7'4 Cycle 5 Reload Mr. Harold R. Denton, Director Office=of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Mr. Denton:
By this letter we retransmit responses to verbal questions. received from Brookhaven National-Laboratory (BNL) regarding the Cycle 5 Safety Analysis Report (Exxon Nuclear Co. Report No.'N-NF-83-85 and XN-NR-83-85, Supp.
1, Rev. 1)'hat was submitted to the NRC in support of the Cycle 5 reload application.
This document has been prepared following corporate procedures which incorporate a reasonable set of controls to ensure its accuracy and completeness prior to signature by the undersigned.
Very truly yours, e
c
. Alexich 1 c,c~l Vice President MPA/bjs cc. John E. Dolan W.G. Smith, Jr.
Bridgman R.C. Callen G. Charnoff E.R.
- Swanson, NRC Resident Inspector Bridgman 8404030385 840328
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Mr. Harold R. Denton AEP:NRC:0860C Attachment fl WHAT ROD BOW PENALTY IS BEING USED FOR WESTINGHOUSE FUELS The basic position with respect to rod bow penalties for Westinghouse fuel is that ENC fuel has more limiting power peaks than Westinghouse fuel so that any rod bow penalties for Westinghouse fuel are bounded by the Exxon analysis with respect to the plant transient analysis.
The ENC thermal hydraulic analysis for Cycle 4 (XN-NF-82-37, Supp 1) identifies MDNBR s of 1.42 and 1.68 for ENC and Westinghouse fuel respectively.
These results are for a core overpower condition (118X RTP) assuming that each fuel type is at the maximum power during Cycle 4.
Thus the Westinghouse fuel is seen to have an 18X MDNBR margin relative to ENC fuel.
The maxiaum FA H was calculated to be 1.28 in Cycle 4 and is calculated to be 1.19 in Cycle 5
for Westinghouse fuel. Therefore, the above mentioned MDNBR margin will be even greater in Cycle 5.
This is believed to bound any rod bow penalties which might b'e applicable to Westinghouse fuel.
42 REPORT XN-NF-83-85, SUPP 1
STATES THAT THE THERMAL-HYDRAULICCCNPATIBILITY OF WESTINGHOUSE - EXXON FUEL "IS UNCHANGED WITH 5X STEAM GENERATOR TUBE PLUGGING."
WHAT IS THE REASONING BEHIND THIS STATEMENTP Exxon Nuclear Co. performed an analysis to calculate primary coolant flow reduction as a function of tube plugging using the LOOPT code.
LOOPT is a multiloop hydraulics code which adjusts parallel loop flow'.
Loop flows are adjusted by balancing the pump head against loop flow resistances.
Pressure drop across the reactor vessel is dependent upon the sum of the flows from the individual loops.
From this analysis, it was determined that there will be a l.lX flow reductions for 5X average tube plugging ~
Since the thermal hydraulic compatibility concerns relative pressure drop and flow diversions, the small flow change should have no effect on the thermal hydraulic compatability.
83 WHAT METHOD WAS USED FOR CREEP COLIAPSE CALCULATION, COLAPSX OR XN-NF-82-06 7 Creep collapse calculations are performed with RGDEX2 and COLAPX codes.
The prior creep collapse criterion, that the cladding had to be free-standing throughout its design life, is satisfied for 17 X 17 fuel up to a peak rod burnup of 40,000-MWD/T.
Collapse of the free standing fuel tubing is predicted to occur after this burnup.
Mr. Harold R. Denton AEP:NRC:0860C Attachment The new criterion is mentioned in XN-NF-82%6.
According to this criterion, the combination of cladding ovality increase and creep down are calculated at a rod burnup of 6,000 MWD/T and it is shown that the combined creep down does not exceed the initial minimum diametral fuel-cladding gap.
This will prevent pellet hangups due to cladding creep, allowing the plenum spring to close axial gaps until densification is complete.
This
.criterion justifies a peak rod design burnup of t47p000 MWD/T. It should be noted that neither the COLPAX code nor the irradiation dependent creep model was changed.
f4 PAGE B 3/4 2-1 OF ATTACHMENT 1 TO AEP:NRC:0860 STATES THAT EXCESS MARGIN OF AT LEAST 10X TO ECCS LIMITS WILL MORE THAN OFFSET THE IMPACT OF INCREASED STEAM GENERATOR TUBE PLUGGING."
HOW IS THE 10X MARGIN CALCUIATEDP The Cycle 5 neutronic analysis using the ENC 3-D XTG code shows a peak F
of 1.40 in Westinghouse fuel at around 100 MWD/T.
With the inclusion of a 3X engineeriny factor, a
5X measurement uncertainty and an llX V(Z)
- factor, F
is expected to be 1.68 in Westinghouse fuel.
This is approximatel) 15X less than the Technical Specification limit of 1.97.
85 THE CYCLE 4 SER STATED THAT THE SCRAM CURVE WAS NON-Q)NSERVATIVE.
A MEETING WITH THE STAFF RESOLVED THIS MATTER.
HOW WAS IT RESOLVED'he Cycle 5 transient analysis used the FSAR scram curve (Fig 3-3 in ENC report XN-NF-82-32 (NP) Revision 2).
06 ENC LETTER, G. C.
COOK TO D. WIGGINZON (ENC IETTER NO. GCC:001:83),
STATES THAT "THE FUNDAMENTAL CONSERVATISM OF ENC S DETERMINISTIC TREATMENZ OF UNCERTAINZIES IN ITS THERMAL MARGIN CALCUIATION IS QUANTIFIED IN ATTACHMENT B BY COMPARISON TO THE RESULTS OF A MORE CORRKT STATISTICAL ANALYSIS."
HAS THE NRC APPROVED THIS METHODOLOGY7 The Cycle 4 transient analyses used a flow uncertainty of 2.1X and the referenced ENC letter (GCC:001:83) was the justification used for that uncertainty.
For the Cycle 5 transient analyses, a flow uncertainity of
Mr. Harold R. Denton AEP: NRC: 086 0C Attachment 3.5X has been used as mentioned in the Unit 2 Technical Specifications.
The primary flow used in Cycle 4 and 5 analyses is shown in the table.
1.
Design thermal flow (lb/hr) 2.
Measured flow (lb/hr) 3.
Tech.
Spec. uncertainty 4.
Penalized flow (lb/hr) 5.
Flow reduction due to S.G.
tube plugging 6.
Flow used in the analysis
( lb/hr) 7.
Cycle 4 SER recommended flow (lb/hr)
I Cycle 4 I
I 142.7 X
I I
I I
I I
I I
I I
l I
142.7 X
I I
[
140.6 X
10
- 10
- 10 Cycle 5
I 144.7 X 10 3.5X 139.6 X 10 138.0 X 10
- Design flow was 2.1X less than the Cycle 3 measured flow of 145.7' 10 6 lb/hr.
07 WHAT WAS THE ACTUAL EOC EXPOSURE FOR CYCLE 42 WHAT AFFECT DOES THIS HAVE ON CYCLE 5 DESIGN PARAMETERS AS TO RELOAD ANALYSIS'he Cycle 5 loading pattern is designed for an end-of-Cycle 4 exposure of 13,400
+ 300 MWD/T.
Since the actual Cycle 4 burnup is 13,628 MWD/T, it is anticipated to result in an increase in Cycle 5 power peaking by no more than 1X.
08 K
HAS AN IMPACT ON SHUZDOWN MARGIN+
HOW DOES THE ACTUAL BURNUP AFFECT SR DOWN MARGIN THROUGH Keff The Cycle 5 safety evaluations and hence the shutdown margin calculation remains valid for an end-of-Cycle 4 burnup of 13,400
+ 1,000 MWD/T.
The actual Cycle 4 burnup is well.within the window of 12,400 MWD/T to 14,400 MWD/T.
~
~
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Mr. Harold R. Denton AEP: NRC: 086 0C Attachment 8'9 FIGURE 3.2 IN XN-NF-83-85 SHOWS A 6% DEVIATION FOR ASSEMBLY H-15.
ON PAGE 4,
THE REPORT STATES THAT THE POWER DISTRIBUTION CALCULATH) BY ENC HAS GENERALLY AGREED TO WITHIN + 5X OF THE MEASURED VALUES.
WHY THIS DISCREPANCYP OVER WHAT EXPOSURE RANGE DOES THE + 5X AGREEMENT APPLY?
The average error (X) in the power distribution reported in Figure 3.2 is 1.5X. The RMS average error is 1.9X.
We do not assert that every assembly will agree within 5X of predictions.
Most distributions of data have a
tail+
In this figure, one out of fifty-six assembly powers exceeded the 5X-.
The calculated assembly powers in Figure 3.2 were obtained using the XTG code.
XTG is capable of calculating relative assembly powers at any point in the cycle and obtaining comparable agreement with measurement.
810 LIST THE REMAINING ENC CODES/METHODS THAT NEED NRC APPROVAL.
The following codes/methods require NRC approval:
a)
PTS-PWR b)
Clad-collapse criterion The following methods require a
SER but have been approved for plant specif ic use:
1)
ECCS 2)
Radio log ical as ses sment