ML19345E985
| ML19345E985 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 01/30/1981 |
| From: | Widner W GEORGIA POWER CO. |
| To: | NRC COMMISSION (OCM) |
| Shared Package | |
| ML19345E986 | List: |
| References | |
| NUDOCS 8102060486 | |
| Download: ML19345E985 (12) | |
Text
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,p NRC DOCKET 50-366 OPERATING LICENSE NPF-5 EDWIN I. HATCH NUCLEAR PLANT UNIT 2 OPERATING LIMIT MCPR Gentlemen:
Georgia Power Companf hereby amends our Unit 2 Reload 1 submittal of October 17, 1980, by providing revised Technical Specification values for the Operating Limit MCPR.
The initial values submitted are based on the results of the.
ODYN analysis performed for Unit 2 Reload I with no adjustment.
However, one of two options must be chosen to adjust-the results of the ODYN analysis.
One method, Option A, provides for a multipli? r to the calculated ODYN values.
The other method, Option B,
utilizes improved performance based on the actual scram times achieved by the unit.
The attached proposed Technical Specifications are based on use of Option B.
Also attached is a summary of the methodology and basis for use of Option B and a derivation of the Operating Limit MCPR values.
The proposed change to the Te:chnical Specifications has been reviewed by the Plant Review Board and the Safety Review Board and has been determined not to involve an unreviewed safety question.
A fee has been previously paid for the Unit 2 Reload 1 revi! w.
Very truly vuurs l
l 2fd.W h l
W. A. Widner RDB/rb Attachments l
Sworn to ano subscribed before me this 30th day of January,1981.
h I
Natary Public.fGptpapyS9tstaligge My Commission Expires Sept. 20,1983 xc:
M. Manry
',,.,,R. F. Rogers, III gg2060 k t
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i HATCH 2 CYCLE 2 MCPR OPERATIf;G LIMIT DETERMINATION MCPR Operating Limit-Background The MCPR limit for each class of fuel historically has been determined by using largest MCPR obtained from analyzing the following transients: loss of 1000 feedwater heating (LOFH), turbine trip / load rejection without bypass (TT/LRWOBP), and feedwater controller failure (FWCF).
The MCPR resulting from the LOFH transient is still based on a REDY analysis, and the method of cal-culating the MCPR has not changed. The pressurization transients TT/LRWOBP and RfCF are now based on ODYN analyses, and the NRC has required that additional conservatism be applied in calculating MCPR (0ption A).
However, the NRC has also allowed the plants to take advantage of the fact that actual control blade scram times to 20% insertion are typically faster than the scram time assumed in the licensing analyses.GE has developed generic adjustment factors based on ODYN analyses run using a scram time based on measured data obtained from several operating plants.
The MCPR operating limits calculated using these adjustment factors (Option B) are less limiting than those calculated using Option A; however, the plant must show that its measured scram times are con-servative with respect to those used in the generic analysis.
Georgia Power has elected to use Option B for determining the MCPR operating limits for Hatch 2 Cycle 2.
EPR Operating Limit Based on LOFH Transient The LOFH transient is analyzed using REDY and neither the Option A penalty
~
nor the Option B adjustment factor is used in calculating the operating limit.
Tne following equation is used:
=
LOFH w'ere n
SL = 1~.07,the MCPR Safety Limitl ACPR = 0.14 (8X8R)
, ACPR resugcing from REDY analysis of the 0.14 (P8X8R) transient Pressurization Transients Option A The NRC requires that an additional 4.4% penalty be added to the operating limit to account for model uncertainties.3 The method of applying the uncertainty, as defined by the NRC,4 is given below:
MCPRA (1.044)(ICPR)
(2)
=
(
and SL =
1.07, MCPR Safety Limit ACPR = 0.17 (8X8R) for LRWOBP 0.17 (P8X8R) 0.15 (8X8R) for FWCF
., ACPR resulting from ODYN 2
analyses of the transient 0.16 (P8X8R)
2 Pressurization Transients (Continued)
Option B The generic adjustment factors used in determining the Option B MCPR's were developed by GE for each class of plant using average scram times to 20% insertion calculated from data collected from several operating plants. Tiae adjustment factors for E0C analyses of BWR 4/5's with RPT are:
-0.024 for TT/LRWOBP.5 5
+0.016 for R4CF The adjustment factors are given in units of ACPR/ICPR, and 'should be added to the ACPR/ICPR calculated based on equation 3.
This relationship is given by the equation:
1 ACPRg ACPR 6
, 4p MCPRB ICPR (4)
Where adjusted ACPR which takes into account the -
ACPRg
=-
adjustment factors, MCPRB = option B MCPR operating limit, ACPR resulting from 0DYN analyses of the ACPR
=
transient, given in reference 2, SL + ACPR, as defined in ' equation 3, and -
=
GE statistical ' adjustment factor described AF
=
above.
Equation 4 may be solved for ACPR, yielding the expression:
B SL[ACPR + AF]
'( }
ACPR B
1-[fCp
+ AF]
PR MCPRg must then be calculated according to t.he. equation:
MCPRB= SL + ACPRB (6)
If-the expression in equation (5)L is substituted in equation (6) for ACPR '
~
B the expression for MCPRB becomes-llCPRB.
'p) 1-' [
R + AF]'
This equation is used for calculating MCPR
- B
~
3 MCPR Operating Limits for Hatch 2 Cycle 2 Equations 1, 2, 3, and 7 were used to calculate the operating limits for 8X8R and P8X8R fuel for the three transients using Option A and Option B as appropriate.
The results of these calculations are given in Table 1.
TABLE 1 MCPR for Hatch 2 Cycle 2 i
LRWOBP FWCF LOFH Unadjusted MCPR (Eqns 1 and 3)
I 8X8R 1.24 1.22 1.21 1
P8X8R 1.24 1.23 1.21 Option A MCPR (Eqn 2) 8X8R 1.29 1.27 NA P8XSR 1.29-1.28 NA Option B MCPR (Eqn 7) 8X8R 1.21 1.24 NA P8X8R 1.21 1.25 NA Implementation of MCPRg and MCPR _
3 i
Both Option A and Option B results have been presented because the Option B limits may be used only when the average measured scram time is less than or equal to the conformance limit TB defined in the Tech Spec.
If the measured average exceeds TB, then the MCPR limits must be determined by. linearly interpolating between MCPRB and MCPRA for each transient. The maximum value of MCPR obtained becomes the MCPR operating limit.
Scram Time Conformance Limit Tg_
The general expression for the conformance limit TB is given by:
TB = -p + 1.65 [n 1
o (8)
I Nj i=1
~
Where p= ' ' average scram time calculated by'GE based on operating plant data o=
standard deviation associated with 'the average scram p;
.provided by GE N1 =. number of control rods measured ~ in initial. scram.
time surveillance at B0C Ng = number of control rods measured in the ith! surveillance test
-n=
number of surveillance tests.
. ~
Scram Time Conformance Limit Tg (Continued)
The values of p and a have been calculated by GE based on data from operating plants and depend on the actual measurement location used by the Plant.
Because the licensing and generic analyses were performed by GE using scram times corresponding to 20% insertion, and 20% insertion is not equivalent to any given notch position, a notch position near 20% insertion must be used.
Because the scram time surveillance Tech Spec for Hatch 2 specifies that surveillance is required at notch 36 (instead of 20% insertion), the conformance pandafornotch36:gfornotch36.
GE provided the following values of limit TB is also defi p=
0.834 sec o=
0.059 see These values correspond to the pick up point of the scram time measurements and are the most conservative (i.e., smallest) values for notch 36. Therefore, the conformance limit will be defined in the Hatch 2 Tech Specs by:
TB 0.834 + 1.65 [ n
]
(0.059)
(9)
=
r Nj i=1 y3 - Scram Time Corresponding to Option A Analysis Ta is defined as the scram time from the 67B scram curve used in the 0DYN deterministic analysis.
This-value is equivalent to the average scram time limit for 20% insertion as defined in the scram time surveillance Tech Specs. Be-cause the Hatch 2 scram time surveillance Tech Specs require a measurement at notch 36 instead of 20% insertion, the scram time limit given in' the Tech Specs is 1.096 sec.
To be consistent with the scram time surveillance Tech -Specs and the definition of the TB conformance limit, Ta = 1.096 sec.
Average Measured Scram Time Tave To determine whether the option B MCPR operating limits can be used, the plant staff must calculate the average scram time to notch 36 using all scram time.
measurements made throughout the cycle to satisfy the scram time surveillance Tech Spec. Thus Tave is a cumulative average over the cycle and is given by:
n 5
E NjTj Tave " "1 (10) n i
N i=1 ;
Where.
number of control rods measured in.the i th -surveillance' tes t.
N
=
j Tj average scram time 'to notch 36 calculated from all measure-
=
ments in the ith surveillance test number of surveillance tests performed to date during the -
n =
cycl e-
5 Definition of the MCPR Operating Limit Over The Range in to rg If the average measured scram time Tav is less than or equal to the conformance limit TB, the operating limit is the maximum value of MCPRB calcu-lated for the three transients.
For Hatch 2 Cycle 2:
1.24 for 8X8R fuel and MCPR
=
1.25 for P8X8R fuel MCPR
=
If Taye is greater than TB, linear interpolation between MCPRB and MCPRA is required.
Figures 1 and 2 show the behavior of the MCPR for each transient over the range TB to TA for 8X8R and P8X8R fuel. As the figures in-dicate, the limiting transient is feedwater controller failure for both fuel types if Tave 1 TB.
However, at some point between TB and TA, the lines cross and LRh'0BP becomes limiting. For Hatch 2, LOFH is never the limiting transient.
As the graphs show, the MCPR operating limit for each fuel type is defined by a single curve composed of two intersecting straight lines.
This curve gives the maximum MCPR for the three transients for any Tave greater than or equal to TB and less than or equal to Ta.
Because the value of TB changes after each scram time surveillance, determining the correct scale to use for the r axis is a difficult task.for the operator.
The alternative of linearly interpolating between MCPRB and MCPRA for each transient and choosing the largest result is also cumbersome in practice.
The third alternative, which is included in the Hatch 2 Tech Specs, is a graphical representation of the linear interpolation calculation.
The equation which would be used to linearly interpolate between the.
two points is:
5
( 'j
- _
8)(MCPRA - MCPR ) + MCPR (11)-
=
B B
where all quantities have been previously defined.
When Tave = TB, MCPR = MCPR, and when.Tave = Ta, MCPR = MCPR -
B A
If we define the parameter Tave - TB 7 =
Ta - TB and plot MCPR as a function of r, we remove the dependence of the, x-axis scale s
on the value of. TB.
Thus the range of the graph is 0 to 1 instead of TB to i.
n
= 1, MCPR = MCPR. In effect, the graphs in When T = 0, MCPR = MCPRB and when T A
figure 3 and 4 tabulate the MCPR for each transient as a function of the parameter used to interpolate between Ta and TB.
Note the similarity to figures 1 and 2.
Figures 5 and 6 show only the limiting MCPR.as a function of T.
These graphs are included in the proposed Tech Spec changes for Hatch 2 Cycle 2. The operator needs only to calculate r and read the new MCPR operating limit directly from the graph.
6 Summary The above discussion documents the calculation of all MCPRs used in determining the MCPR operating limits, the equations used in all calculations, and all constants used in the calculations or defined in the Tech Specs. These results are based on GE recommendations and on our understanding of the current NRC requirements for the implementation of ODYN. While the preceding discussion of the equations, constants, and procedures for determining the MCPR operating limit graphs are complex, we believe the resultant Tech Specs give the simplest method for implementing Option B.
N N
REFERENCES 1.
"Edwin I. Hatch Nuclear Plant Unit 2 Technical Specifications" Appendix A to License No. NPF-5, Georgia Power Company.
2.
G. Zanardi, " Supplemental Reload Licensing Submittal for Hatch Nuclear Power Station Unit 2 Reload 1," Y1003J01A10, General Electric Company,1980.
3.
Letter from R. P. Denise (NRC) to G. G. Sherwood (GE), dated January 23, 1980.
4.
R. T. Hill, personal communication, January 5,1981.
5.
Letter from R. G. Buchholtz (GE) to P. S. Check (NRC),
" Response to NRC Request for Information on ODYN Computer fbdel," dated September 5,1980.
6.
Letter from R. T. Hill (GE) to N.S. Folk (SCS), "0DYN Adjustment Factor Application," dated December 30, 1980.
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=
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ir T
1.21 T
TB A
Tave MCPR LIMIT FOR 8X8R FUEL AT RATED FLOW FIGURE 1 e
1.29
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l.26 e'
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'MCPR LIMIT FOR P8X8R FUEL AT RATED FLOW FIGURE 2
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mm m
9 9
9 S.k a
ve o
ng:,
1.29
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1.27
..'s'
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7 Xb' 1.26 1.25 f
, /
1.24 [
/
1.23 1.22 1.21 0.0 0.2 0.4 0.6 0.8 1.0
~
T MCPR LIMIT FOR 8X8R FUEL AT RATED FLOW FIGURE 3 L
1.29 gy
,L.
/
1.28 fe w
,pe 1.27 1.26
,/
1.25 =
1.24
. 1.23 a
1.22 2
mf
^ 4*
1.21.'
O.0 0.2 0.4 0.6
- 0. 8 -
-1.0 1
MCPR LIMIT FOR P8X8R FUEL AT RATED' FLOW
~
FIGURE 4-
^
S
.a t-1.29
/=
/
1.28
,/
/
1.27
,/ -
1.26
,[.
/
2 s'
1.23 N
1.24 7' -,
-1.23 1.22; 1.21 _2 0.0 0.2 0.4, 0.6 0.8 1.0 i
MCPR LIMIT FOR 8X8R FUEL AT RATED FLOW FIGURE 5 L
1.29
,1 1.28 1.27
/
I'.26
/
2 1.25 rf
~
M 1.2A 1.23
~
1.22 1:21
~0.0' 0.2-0.4 0.6 0.8.
- 1. 0' r
MCPR LIMIT FOR P8XBR FUEL AT. RATED FLOW
' FIGURE 6
-