ML20093C801
| ML20093C801 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/05/1995 |
| From: | James Knubel GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C311-95-2406, NUDOCS 9510130028 | |
| Download: ML20093C801 (7) | |
Text
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e GPU Nuclear Corporation Route 441 South k
@3lggf P.O. Box 480 Middletown. Pennsylvania 17057-04d (717) 944 7621 Writer's Direct Dial Number:
October 5, 1995 C311-95-2406 U. S. Nuclear Regulatory Commission Att: Document Control Desk Washington, DC 20555 Gentlemen:
Subject:
Three Mile Island Nuclear Generating Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Response to Request for Additional Information - Core Reload Methodology NRC letter dated August 23,1995 requested additional information~ regarding GPU Nuclear Topical Report TR-091, Revision 0, " Steady State Reactor Physics Methodology for TMI-1."
This Topical Report was submitted by GPU Nuclear on March 6,1995 for NRC review and approval for in-hobse GPU Nuclear core reload design.
The attachment provides an itemized response to each of the NRC questions, if any additional inforrnation is required, please contact Mr. David J. Distel, GPU Nuclear Licensing at (201) 316-7955.
Sincerely, W v J. Knubel Vice President and Director, TMI i
DJD/ pip Attachment c:
Administrator, Region i TMI Senior Resident inspector NRC Senior Project Manager, TMl-1 1nnnnm 9510130028 951005 PDR ADOCK 05000289 P.
..PDR
{l GPU Nuclear Corporaton is a subsidiary of General Pubhc Utihties Corporation 1
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ATTACHMENT 1.0 QUESTIONS 1.
In section 6.0, Reliability Factors, page 103 of the reference document you state:
"These values are typical of the values used in reload analysis, but they will be evaluated and revised if needed, as more operation data is available."
A.
What type of analyses will be performed on subsequent cycle data and what criteria will you use to decide if reliability factors need revision?
B.
If reliability factors need to be revised what mechanism do you plan to use to affect this change?
RESPONSE
Section 6.0 of TR-091 describes the methodology used to determine various "95/95" reliability factors based on comparisons between measured and calculated values.
Because the current safety analyses (TMI-l FSAR Chapter 14) use bounding values for most key physics parameters, not all reliability factors calculated in Section 6.0 are utilized. The reliability factors for regulating control rod group worth, radial peak pin, and total peak pin are directly used in the determination of Reactor Protection System (RPS) trip setpoints and alarm limits. Their application is described in TR-092, "TMI-l Reload Design and Setpoint Methodology," which will be submitted to NRC in October 1995.
When subsequent cycle data are available, they will be added to the database. The impact of these data on the reliability factors will then be evaluated. It is likely to have some effect on the reliability factors for the Hot Zero Power (HZP) Beginning of Cycle (BOC) parameters due to the small size of the database. These reliability factors will be redetermined using the method described in Section 6.0. However, changes in these reliability factors would not have any impact on the safety limits and core operating limits since these reliability factors are not applied in current safety analyses (bounding values used).
The added data is unlikely to affect the power peak reliability factors because of the large number of data in the database. These power peak reliability factors are generally considered cycle independent. However, if the root-mean-square (RMS) errors of the new cycle's power comparison differ significantly from those of previous cycles (typically less than 2% for the radial power and less than 5% for total power),
the cause of the deviation will be investigated and the impact on the power peak reliability factors will be evaluated.
3 Attachment Page 2 of 4 If the comparisons worsen, the power peak reliability factors will be revised.
However, it is not necessary to revise the power peak reliability factors if the
, comparisons improve, unless more operational margin is desired. Should there be a need to change the power peak reliability factors, they will be redetermined by applying the methodology given in Section 6.0 and will be documented in the cycle's reload analysis calculation package.
2.
Ilow do the reliability factors listed in Section 6 compare with those being used for your current safety analyses?
RESPONSE
Not all the reliability factors listed in Section 6.0 are used in current safety analyses.
The reliability factors for radial pin peak, total pin peak and regulating control rod (CR) group worth are directly used in determining the reactor protection system power / imbalance / flow trip setpoints, power imbalance alarm limits and control rod insertion limits. The reliability factor for control rod worth is the same as the current value. The reliability factors for radial and total pin peak are quite close to the current values. The current values are determined by Babcock and Wilcox (B&W)
Fuel Company based on CASMO-3/NEMO. The reliability factors are compared below:
Reliability Factor TR-091 CURRENT Regulating CR Group Worth
-10 %
-10 %
Radial Pin Peak 1.035 1.038 Total Pin Peak 1.055 1.048 The differences in the peak power reliability factors are due to the differences in the l
computer codes (SIMULATE-3 versus NEMO). Improvement in the total pin peak reliability factor is expected if SIMULATE-3, instead of NEMO, is used to generate the input for the plant process computer.
Attachment -
Page 3 of 4 i
i 3.
. What values of the reliability factors do you propose using to set plant safety limits?
1
RESPONSE
To be consistent with the methodology developed at GPU Nuclear, the reliability factors for the regulating control rod group worth, radial pin peak and total pin peak determined in TR-091 should be used to set plant safety limits. Since the current reliability factor for radial pin peak (1.038) bounds the 1.035 value determined in TR-091, the 1.038 value will be used for conservatism. Therefore, we propose to use j
the following reliability factors to set plant safety limits:
Reliability Factor.
Value Regulating CR Group Worth
-10%
Radial Pin Peak 1.038 Total Pin Peak 1.055 l
As shown in the Table provided in response to Question 2, these reliability factors to 1
be used by GPU Nuclear in establishing plant safety limits are the same or bound those used by Babcock and Wilcox in current reload analysis methods.
i 4.
What effect will the use of these new reliability factors have on existing plant
]
l operating limits?
l
RESPONSE
Since the reliability factors determined in TR-091 are either the same or close to the current values (see answers to Questions 2 and 3), the impact of using the new reliability factors on existing plant operating limits is insignificant. As shown in the attached Figures I and 2, the power imbalance alarm limits and control rod insertion
' limits generated with GPU Nuclear methodology are essentially the same as the
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Attachment 4
Page' 4 of 4 1
vendor results. The Cycle 10 limits are determined using the following reliability factors:
i Reliability Factor GPUN Vendor.
Regulating CR Group Worth
-10%
-10%
1 Radial Pin Peak 1.038 1.038 Total Pin Peak 1.055 1.048 TR-092, "TMI-1 Reload Design and Setpoint Methodology," will document the -
i I
application of the new reliability factors as compared to our current plant operating limits for Cycle 10.
1 a
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4 4
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4 Figure 1 Power Imbalance Alarm Limits (0-to-75 EFPD and 4 Pump Operation) 140 0 Vendor Results a GPUN Results 120 -
100 80 -
E Restricted 89' "
6 Restricted i
h 80 "
Permissible E
Operating W 60 -
Region 5
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40 20 -
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-40
-30 20
-10 0
10 20 30 40 50 Axial Power Imbalance (%)
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'a Figure 2 Control Rod insertion Limits (0-to-75 EFPD and 4 Pump Operation) 140 -
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+ Vendor Limits (LOCA)
-A-GPUN Limits (LOCA) 120
+ Vendor Limits (SDM)
-X-GPUN Limits (SOM)
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100 Not Allowed l
3 80 t!
Restricted E
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0 25 50 75 100 125 150 175 200 225 250 275 300 Control Rod Position (% Withdrawn)
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