ML20211A837
| ML20211A837 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/08/1986 |
| From: | Papanic G YANKEE ATOMIC ELECTRIC CO. |
| To: | Mckenna E Office of Nuclear Reactor Regulation |
| References | |
| DCC-86-157, FYR-86-097, FYR-86-97, NUDOCS 8610170043 | |
| Download: ML20211A837 (8) | |
Text
g YAN,KEE ATOMIC ELECTRIC COMPANY wwho"' (* ") * ' ' 00 TWX 710-380-7619
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A 1671 Worcester Road Framingham, Massachusetts 01701 DCC 86-157
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October 8, 1986 FYR 86-097 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Eileen M. McKenna, Project Manager Project Directorate #1 Division of PWR Licensing-A
Reference:
(a) License No. DPR-3 (Docket No. 50-29)
(b) YAEC Letter to USNRC, dated July 31, 1986 Subj ect:
Technical Specification Governing Operation of the Incore Instrumentation System - Additional Information
Dear Ms. McKenna:
During discussions with your staff regarding Proposed Change
- 200 [ Reference (b)], a request was made for additional information about the technical data supporting the change. Attached is a technical discussion which describes the analysis performed in support of
-this prcposed change. We trust that you will find this information satisfactory. However, should you desire further information, please contact ud.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY m
George panic, Jr.
Senior Project Engineer Licensing GP:kem f
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.8610170043.861008 PDR ADOCK 05000029-l
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F YANKEE ATOMIC ELECTRIC COMPANY TECHNICAL DISCUSSION PROPOSED CHANGE #200 BACKGROUND Technical Specifications require a minimum of twelve (12) incore instrumentation neutron detection thimbles with two per core quadrant for power distribution limit surveillances. At the present time, only 13 instrumentation thimbles are available. Present measurement uncertainties utilizing less than 17"but greater than or equal to 12 thimbles requires an uncertainty of 6.8% to be included in the calculation of the 1) heat flux power peaking factor, F
- 2) nuclear enthalpy rise hot channel factor F AH, and 3) peak full power linear heat generati$n rate, LHGR (kw/f t).
Due to the possible unavailability of additional incore thimbles, thus reducing the number of available thimbles to below required values, a technical specification change for system operability and concurrent application of uncertainties is proposed for the remainder of Yankee Cycle 18 operation.
DISCUSSION Compliance to Technical Specification 3/4.2 is verified every 1000 EFPH (approximately 1400 Mwd /Mtu). A full set of traces based on the available thimble locations cre taken and analyzed with the INCORE computer code. From the measurement, power distribution values are obtained and compared to technical specification limits.
Presently, application of the 6.8% measurement uncertainty used for the operable incore neutron detector thimbles is multiplicative in the calculation of Fq l
l cnd F This 6.8% uncertainty, along with the power level uncertainty and AH.
l
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heat flux engineering factor, is also combined statistically as the " root-sum-square" for the calculation of peak LHGR values. The proposed change wo"1d use the same application of uncertainties but with 8% used to replace the 6.8% when the number of available (OPERABLE) incore neutron detection thimbles falls below 12 but remains greater than or equal to 9.
The requirement of at least 1 OPERABLE thimble per core quadrant would also be imposed.
In order to justify the 8% uncertainty, an analysis was performed in which previous cycle full power measurements were reanalyzed such that only 9 incore traces were represented, but with at least one thimble per core quadrant.
Figure 1 shows the 12 randomly selected patterns of 9 thimble locations. Using the present 13 thimble locations, twelve random patterns with 9 available locations were analyzed and the least conservative Fq, FAH, and LHGR values predicted were compared to previous actual incore measurements.
If the values calculated using 9 incore traces (and 8% uncertainty) were greater than the actual measurements utilizing the total available number of incore thimbles (and 6.8%) then the 8% uncertainty is justified. Table 1 presents Fq, FAH, and LHGR measured values using the 6.8% uncertainty for three Yankee operating cycles (16-18) and the least conservative values obtained using the 8% uncertainty applied when 9 incore thimbles traces are used. As shown, all values utilizing 9 incore thimbles j
sre greater than or equal to actual plant incore runs with the exception of I
cae F value. This exception is deemed insignificant since the F limit aH AH of 1.8 provides a 10% margin.
Previous operating cycle data has been included as requested. The heat flux power peaking factor, Fq, and the nuclear enthalpy rise hot channel factor, v.
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F F33, measured values for Cycles 16-18 are shown in Figures 2 and 3 respectively.
As shown, the values have remained constant from cycle to cycle and have maintained a similar slope as a function of exposure. The peak full power linear heat generation rate, LHGR, is constructed from measured Fq values and a set of uncertainties. The LHGR would therefore show the same trend as the Fq plot if a constant set of uncertainties had been applied over the past operating cycles.
Based on the patterns of 9 instrumentation thimbles examined and past operating consistency, Yankee feels that a minimum of 9 thimbles, one per quadrant, with cn 8% uncertai,nty is appropriate for the remainder of Cycle 18 full power operation.
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COMPARISON OF FAH, FQ. AND LHCR(KW/FT)
FRESH FUEL - CYCLES 16-18 l
FAH TO LHCR(KW/FT)
IN00RE RUN EXPOSURE BASE WORST
% DIFF BASE WORST
% DIFF BASE WORST
% DIFF NUMBER MWD /MTU CASE CASE CASE CASE CASE CASE YR-18-013 1.172 1.600 1.412 0.8 2.342 2.349 0.3 10.137 10.149 0.1 YR-18-028 7.270 1.572 1.577 0.3 2.051 2.057 0.3 9.261 9.268 0.1 i
YA-16-036 13.565 1.511 1.524 0.9 1.855 1.872 0.9 8.900 8.961 C.7 YR-17-012 1.337 1.541 1.546 0.3 2.192 2.205 0.6 9.534 9.572 0.4 YR-17-019 7.000 1.516 1.530 0.9 1.986 2.002 0.8 8.995 9.048 0.6 YR-17-023 11.840 1.474 1.490 1.1 1.906 1.924 0.9 8.990.
9.058 0.8 YR-18-010 1.738 1.628 1.629 0.1 2.287 2.295 0.3 9.683 9.698 0.2 YR-18-014 6.592 1.578 1.587 0.6 2.039 2.045 0.3 8.671 8.677 0.1 l
BURNT FUEL - CYCLES 16-18 l
FAH TO LHGR(KW/FT)
INCORE RUN EXPOSURE BASE WORST
% DIFF BASE WORST
% DIFF BASE WORST
% DIFF NUMBER MWD /MTU CASE CASE CASE CASE CASE CASE YR-14-013 1.172 1.663 1.677 0.8 2.374 2.400 1.1 10.277 10.365 0.9 YR-16-026 7.270 1.592 1.601 0.6 2.042 2.047 0.2 9.220 9.224 0.1 YR-16-036 13.565 1.500 1.512 0.8 1.834 1.843 0.5 8.801 8.828 0.3 YR-17-012 1.337 1.644 1.656 0.7 2.281 2.296 0.7 9.921 9.969 0.5 YR-17-019 7.000 1.598 1.607 0.6 2.056 2.070 0.7 9.311 9.354 0.5 I
YR-17-023 11.840 1.543 1.555 0.8 1.957 1.971 0.7 9.229 9.276 0.5 YR-18-010 1.738 1.828 1.622
-0.4 2.275 2.282 0.3 9.633 9.642 0.1 YR-18-014 6.592 1.578 1.578 0.0 2.014 2.022 0.4 8.567 8.582 0.2 l
BASE CASE : MEASURED WITH 6.8% INSTRUMENTATION UNCERTAINTY.
WORST CASE : MEASURED WITH 8.0% INSTRUMENTATION UNCERTAINTY.
WORST CASE - BASE CASE
% DIFF = --------------------- X 100.0 BASE CASE l
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FIGURE 1 LOCATIONS OF INSTRUMENTATI0ii THIMBLES PATTERNS #1 - #12 i
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I FIGURE 2 YANKEE CORES 16-18 F0 VS. EXPOSURE 3.0 l
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FIGURE 3 YANKEE CORES 16-18 l
F-DELTA-H VS. EXPOSURE l
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+ - CYCLE 18 1.8 : :
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