ML20039A145
| ML20039A145 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/08/1981 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8112160271 | |
| Download: ML20039A145 (7) | |
Text
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SOUTH CAROLINA ELECTRIC a GAS COMPANY
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December 8,1981 wu pu.,=c... o.oo, cuco t G, Q uan. o 4
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$_,6, [D Mr. Harold R. Denton, Director V,
Office of Nuclear Reactor Regulation Ty U. S. Nuclear Regulatory Cmrtission 1
Washington, D. C.
20555
Subject:
Virgil C. Sununer Nuclear Station Docket No. 50/395 Technical Specifications
Dear Mr. Denton:
In the review of the draft Technical Specifications for the Virgil C. Smmer Nuclear Station the NRC Technical Specification reviewer requested documentation be subnitted to support the 1.75%
measurenent uncertainty value for reactor coolant flow in Technical Specification 3.2.3 (page 3/4 2-8).
Originally, a value of 3.5% was subnitted, however, the reduction is justifial by the performance of a flow measurement calorimetric to determine total reactor f1cw instead of using an elbow tap reading. his eliminated the 1.5%
error allowance associated with elbow tap repeatability. %c remaining.25% error reduction was accmplished by statistically combining errors. Statistical cmbination of errors is justified by WCAP-8567 (acceptal by NRC on 4-19-78 by letter from Mr. John Stolz to Mr. Clem Eicheldinger of Westinghouse.)
Specification 3.2.3, RCS Flow Rate and Nuclear Enthalpy Rise Hot 01annel Pactor, in the Standard Technical Specifications requires that total reactor flow (total flow through the vessel frm all loops) be above some minimum value and if above that minimum value allows a trade off between rod bow penalty and reactor flow. We minimum flow value is thermal design flow corrected for flow measurement uncertainties. Historically, the uncertainty has been specified as 3.5%.
Flow measurement uncertainties nuch less than this can be achieved however by using modern statistical error combination techniques and a calorimetric flow measurement method.
We accuracy claimed for this technique depends primarily on the measurement Irocedure snployed and on how well the instrument errors are understood and controlled by plant persor.nel. We calorimetric flow calculation, the measurements required ard the measurenent uncertainty analysis are described in the follow!rg paragraphs and tables.
Reactor coolant loop flow is determined from the' steam generator thermal output, corrected for the loop's share of the net pwp heat 00f
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input, and the enthalpy rise ( a h) of the coolant. 'Ibtal reactor flow is the sun of the individual'1oop flows. Table 1 lists the 5
calorimetric equations and defines the terms.
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'Mr. Harold R. Denton
% r 8, 1981-Page 2 To establish the overall flow measurement uncertainty, the accuracy and relationship to flow of each instrument used for the -
calorimetric measurements (see Table 2) nust be determined. In most cases, there are several components (transducer, converter, isolator, readout device, etc.) which contribute to the overall uncertainty of the measurement. Table 3 provides a list of typical cmponents involved in the calorimetric loop flow measurement,' a corresponding conservative instrument error allowance and the effect of the instrment-error allowance. on the calculated power or flow value.
'Ibe overall loop flow measurement uncertainty.is the statistical cmbination of the individual uncertainties and appears at the bottcm of Table 3.
Total reactor flow measurement uncertainty,'which is the statistical cabination of the individual loop flow uncertanties, also appears at the bottm of Table-3.
In summary, individual loop flow is determined by performance of a calorimetric and these values are surrmed to arrive at total reactor flow. The measurement uncertainty is determined by statistically cmbining individual cmponent and loop uncertainties. A calorimetric flow measurement nust be performed to take credit for
-this particular measurement uncertainty.
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Mr. Harold R. Denton December 8,1981 Page 3 1
TABLE 1 RFJCIT)R COOLANT IOOP FILW CAICULATICN-g = 8.02
[Qg + (Q /N g)] / [h -hl
'Y H
e c
Where:
W
= Loop flow (GIN) g Q
= Steam generator thermal output (BN/hr.)
SG Q
= Primary system net heat losses (BIU/hr.)
N
= Number of loops O
= Reactor coolant pump heat adder (BW/hr.)
p h
= Hot leg enthalg. (Bm/lb.)
H h
= cold leg enthalpy (BW/lb.)
c v
= cold leg specific volume (Cu. Ft./lb.)
c (0 /N-O ) = -3.4 x 10 BW/hr.
3 p
Q
= (h -h)W SG s
f p
Where: h
= Steam enthalpy (BN/hr.)
s h
= Feedwater enthalg (BW/hr.)
p W
p A P)
W = K F, (Pp p
Where: K
= Feedwater venturi flow coefficient F
= Peedwater venturi coiMon for thermal expansion a
P
= Feedwater density (LB./cu._ft.)
p AP
=Feedwaterventuripressuredrop(inchesIg0)
Mr. Harold R. Denton Wwr 8,1981 Page 4 TABLE 2 MEASUREMENTS REQUIRED 1
Parameter Instrument Ebnction 1.
Ebedwater venturi Barton gauge Ebedwater flow Iressure differential 2.
Ebedwater tmperature RrD Feedwater enthalpy and density Venturi thermal expansion 3.
Steam pressure Transducer Ste m enthalpy 4.
Feactor coolant T Narrow range RID RCS hot leg enthalpy 5.
Reactor coolant T range M RCS cold l g oold enthalpy Rm specific volume 6.
Reactor coolant pressure Transducer RCS enthalpy and specific volume Other information required for the calculation is as follows:
7.
Ebedwater venturi coefficient frm vendor calibration.
8.
Steam generator blowdown secured during the measurement.
9.
Primary systs heat losses and psnp heat input obtained frm calculations. This quantity is the difference between.the NSSS Power 2,785 E and h Rea m h r 2,775 W
- t t
Mr. liarold R. Denton December 8,1981 Page 5.
TAntE 3 CAII)RIPETRIC ETM PEASU15ENT UNCFRfAINTIES Uncertainty-Instrunent
%~ Power or Caponent Uncertainty
% Flow Pbedwater Flow Venturi K 10.5% K 10.5%
'Ihermal Expansion coefficient
'Ibmperature
- 12. 0' F Material 15.0%
10.06%
Density
'1bmperature 12.0'F 10.09%
Pressure 160 psi DP Cell Calibration 10.5%'
10.39%
DP Cell lealing Uncertainty 11.0%
10.78%
Ebalwater Enthalw
'Ibmperature 12.0*F 10.28%
Pressure 160 psi Steam Enthalpy Transducer Calibration 118 psi 10.07%.
Isolator Calibration 118 psi 10.07%
Moisture Carryover 10.25%
10.22%
Primary Enthalpy RfD 10.2*F 10.38%
R/E (bnverter 10.6*F 11.13%
Italout 10.1*F 10.19%
l Temperature Streaming 11.2*F 12.27%-
Pressure Effect 130 psi 10.24%-
RfD 10.2*F 10.31%
R/E Converter 10.6'F 10.94%
lemlout-10.1* F 10.16%
Pressure Effect 130 psi 10.06%
Net Pump Heat Addition -
'120%
10.085%-
l l Total Icop' Flow Uncertainty.
([e) f2.974%
Total Ikactor Flow Uncertainty l.
4-loop 11.5%
3-loop.
11.75%-
f 2-loop 12.1%1
Mr. Harold R. Denton December 8,1961 -
Page 6 TABIE 3 '(Continued)
ASSUMPTIONS
'1he values in Table 3 are based on same specific assumptions about the instr ments and readouts.
1.
Beedwater flow is obtained from several readings of Barton differential pressure gauges installed on the feedwater venturi.
- 2.. 'Ihe measurement is performed soon after a calibration eliminating consideration of instrment drift.
3'.
Credit was taken for the 3 tap scoop RPD bypass loop in reducing uncertainties due to streaming.
1
5 'i 4 3-
~Mr. Harold R.-Denton Deceber 8,1981 Page 7
'Ihis information, W11ch should be trovided to the Technical Specification reviewer and the Core Performance Branch, should be sufficient to justify this change for our plant.
If you have any
- que_ scions, please let us know.
.Very truly yours,
/1.
T. C. Nichols, Jr.
i RBC 'IEN:Ikb cc:
V. C. Sunner T. C. Nichols, Jr.
G. H. Fischer H. N. Cyrus H.'T. Dabb D. A. Nauman M. B.14titaker, Jr.
W. A. Williams, Jr.
O. S. Bradham R. B. Clary M. N. Browne A. R. Koon-G. J. Braddick
.J. L. Skolds.
J. B. Knotts, Jr.
B. A. Bursey J. C. Ruoff L. D. Shealy J. B. Cookinham NPCF File 4
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