ML20095K816
| ML20095K816 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/21/1995 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9512290284 | |
| Download: ML20095K816 (9) | |
Text
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St. llen Support Oscartmsett '
., p.
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. ~~;7 PECO; ENERGY
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g 965 Chestertwook Boulevard Wayne, PA 19007-5691 December 21,1995 Docket No. 50-352 License No. NPF-39 l
U. S. Nuclear Regulatory Commission Attn:. Document Control Desk Washington, DC 20555
SUBJECT:
Limerick Generating Station, Unit 1
. Re'sponse to Request for Additional Information Regarding Technical Specifications Change Request No. 95-03-1 Gentlemen:
l Attached is our response to your Request for Additional Information (RAl),
L discussed in our telephone conversation on December 18,1995 regarding the change in the Minimum Critical Power Ratio (MCPR) Safety Limit due to the planned use of GE13 fuel product line at Limerick Generating Station (LGS),
Unit 1. The new MCPR Safety Limit is the subject of Technical Specifications Change Request No.'95-03-1 which was forwarded to you by letter dated June 19, 1995.
l Using the same methodology described in tne GE report NEDO-24229-1, " Peach Bottom Atomic Power Station Units 2 and 3 Single-Loop Operation," dated l
l May 1980, which was forwarded to you by GE on December 18,1995, the l
resulting MCPR Safety Limit for single loop operation with GE 13 fuel at LGS Unit 1 !s 1.11. The method used for the MCPR Safety Limit calculation for dual loop and single loop operation is identical; the observed 0.02 MCPR difference is due to the increased core flow measurement uncertainty (i.e.,
from 2.5% to 6%) and the increased process computer Traversing in-Core Probe (TIP) uncertainty (i.e., from 8.7% to 9.1%) resulting in a MCPR Safety Limit value of 1.11 for single loop operation.
I 290010 9512290284 951221 PDR ADOCK 05000352
}'
P PDR
i e
Decernber 21,1995 -
Page 2 l
This information is being submitted under affirmation, and the required affidavit is enclosed.
)
If you have any questions, please do not hesitate to contact us.
Very truly yours,
$ YA$lymn G. A. Hunger, Jr.,
Director - Licensing Attachment Enclosure cc:
T.T. Martin, Administrator, Region I, USNRC (w/ attachment / enclosure)
N.S. Perry, USNRC Senior Resident inspector, LGS (w/ attachment / enclosure)
R.R. Janati, PA Bureau of Radiological Protection (w/ attachment / enclosure)
)
l
.l.
COMMONWEALTH OF PENNSYLVANIA ss.
COUNTY OF CHESTER D. B. Fetters, being first duly sworn, deposes and says:
That he is Vice President of PECO Energy Company, the Applicant herein; that he has read the enclosed response to the NRC Request for Additional Information involving the change in the Minimum Critical Power Ratio (MCPR)
Safety Umit due to the use of GE13 fuel product line concerning Technical Specifications Change Request No. 95-03-1 for Umerick Generating Station, Facility Operating Ucense No. NPF-39, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.
'w
. a eh Vice President Subscribed and sworn to before me thisc?/5fday of 995.
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_Rublic m m=, _~
iin/cdE"d3@!a:iVL s
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I ATTACHMENT 1
i LIMERICK GENERATING STATION UNIT 1 l
DOCKET NO.
50-352 LICENSE NO.
NPF-39 EXCERPT FROM NEDC-31300 " SINGLE -LOOP OPERATION ANALYSIS FOR LIMERICK GENERATING STATION UNIT 1", DATED AUGUST 1986 (5 PAGES) i a
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2'.
MCPR FUEL CLADDING INTEGRITY SAFETY LIMIT.-
i
~Except for core total flow and TIP reading, the uncertainties used in the ' statistical analysis to determine the MCPR fuel cladding integrity safety limit are not dependent on whether coolant flow is provided by'one or j
two recirculation. pumps.
Uncertainties used in the two-loop operation
{
-analysis are documented in the FSAR. A 6% core flow measurement uncertainty has been established for single-loop operation (compared to 2.5% for two-l loop operation). As shown.below, this value conservatively reflects the one standard. deviation (one sigma) accuracy of-the core flow measurement system documented in Ref erence 1.
The random noise component of the TIP reading uncertainty was revised for SLO to reflect the operating plant test results ~
given in Subsection 2.2.
This revision resulted. in a process computer effective TIP uncertainty of 6.8% for initial cores and 9.1% for reload cores.
Comparable two-loop process computer uncertainty values are.6.3% for initial cores ' and 8.7% for reload cores.
The net effect of these two revised uncertainties is a 0.01 incremental increase in the required MCPR fuel cladding integrity safety limit.
l 2.1 CORE FLOW UNCERTAINTY 2.1.1 Core Flow Measurement During Single-Loop Operation The jet pump core flow measurement system is calibrated to measure core flow when both sets of jet pumps are in forward flow; total core flow is the sum of the indicated loop flows.
For SLO, however, some inactive jet pumps will be backflowing (at active pump speeds above approximately 40%).
Therefore, the measured flow in the backflowing jet pumps must be subtracted from the measured flow in the active loop to obtain the total core flow.
In addition, the' jet pump coefficient is different for reverse flow than for forward flow, and the measurement of reverse flow must be modified to account:for this difference.
2-1
j s'
In SLO, the total core flow is derived by the following formula:
/TotalCore)j T
Active Loop Inactive L p
(
j Indicated Flowjl
-C Flow Indicated Flow The coefficient C (=0.95) is defined aa the ratio of " Inactive Loop True Flow" to " Inactive Loop Indicated Flow".
" Loop Indicated Flow" is the flow measured by the jet pump " single-cap" loop flow summers and indicators, which are set to read forward flow correctly.
i The 0.95 factor is the result of a conservative analysis'to appropri-ately modify the single-tap flow coef ficient for reverse flow.
If a more exact, less conservative, core flow is required, special in-reactor cali-bration tests can be made.
Such calibration tests would involve:
calibrating core support plate 6P versus core flow during one-pump and i
two-pump operation along the 100% flow control line and calculating the correct value of C based on the core support plate 6P and the loop flow indicator readings.
2.1.2 Core Flow Uncertainty Analysis The uncertainty analysis procedure used to establish the core flow uncertainty for SLO is essentially the same as for two-pump operation with some exceptions.
The core flow uncertainty analysis is described in Reference 1.
The analysis of one-pump core flow uncertainty is summarized below:
For SLO, the total core flow can be expressed as follows (refer to i
Figure 2-1):
1 W
~
C A
I where:
W
=t a core flow, C
W = active loop flow, and W = inactive loop (true) flow.
7 The analytical expected value of the "C" coefficient for Limerick is 0.84.
2-2
3 NEDC-31300 By applying the " propagation of errors" method to the equation above, the variance of the total flow uncertainty can be approximated by:
[
Y,o
+[a 2
z 2
2 2
c
. o
+
t a
+
o W
I~"
N l~"
w C
C sys A
I rand rand where:
uncertainty of total core flow;
=
WC uncertainty systematic to both loops; o
=
gsys random uncertainty of active loop only; o
=
g Arand random uncertainty of inactive loop only;.
o
=
g l
Irand uncertainty of "C" Coefficient; and a
=
ratio of inactive loop flow,(W ) to active loop flow (W )*
a
=
7 A
From an uncertainty analysis, the conservative, bounding values of a
o o
and o are 1.6%, 2.6%, 3.5%, and 2.8%, respectively.
- W878, W^
W C
rand rand Based on the above uncertainties and a bounding value of 0.36 for "a", the variance of the total flow uncertainty is approximately:
l l
l 2
1 2
0.36 on (1.6)2 +
1-0.36 (2.6)2 +
1-0.36 (3.5)2 + (2.8)2 W
=
C l
= (5.0%)2 i
l This flow split ratio varies from about 0.13 to 0.36.
The 0.36 value is a conservative bounding value.
The analytical expected value of the flow split ratio for Limerick is 0.33.
s 2-3
- -. ~
1 i
~
When the effect of 4.1% core bypass flow split uncertainty. at 12%
(bounding case) bypass flow fraction is added to the total core flow uncer-tainty, the active coolant' flow uncertainty is:
0 (5.1%)2 (5.0%9
+
(4.1%)
=
=
ctive g_
2 coolant which is less than the 6% flow uncertainty assumed in the statistical
- analysis, e
In summary, core flow during SLO is njeasured in a conservative way and its uncertainty has been conservatively evaluated.
2.2 TIP READING UNCERTAINTY To ascertain the TIP noise uncertainty for single recirculation loop operation, a test was performed at an operating BWR.
The test was performed at a power level 59.3% of rated with a single recirculation pump in opera-tion (core flow 46.3% of rated).
- A rotationally symmetric control rod pattern existed during the test.
Five consecutive traverses were made with each of five TIP machines, giving a total of 25 traverses.
Analysis of this data resulted in a nodal TIP noise of 2.85%.
Use of this TIP noise value as a component of the process computer total uncertainty results in a one-sigma process computer total effect TIP uncertainty value for SLO of 6.8% for initial cores and 9.1% for reload cores.
e i
L t
2-4
NEDC-31300 CORE b
t k
i
- C W,
"A l.
l W
TOTAL CORE F' OW C
W ACTIVE LOCP FLOW
(
4 W
g INACTIVE LOCP FLOW l
l l
j Figure 2-1.
Illustration of Single Recirculation Loop Operation Flows 2-5
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