ML20086D791
| ML20086D791 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 11/20/1991 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML20086D789 | List: |
| References | |
| NUDOCS 9111260261 | |
| Download: ML20086D791 (9) | |
Text
A p,
e adas Aa
.p Su 4Ju J=.M---2+4i-e A#e A.
44
-m---M-<h>4.-4Gw4. ae> 4 + A-64r
-ictda Ae >M A *e # 44hM, 4444-a_Wve.u-+r4--2..s,a.J A-mm 4
-w asa_mm4 m
44.-
.14,,
p 4
O e
4 e
t W
w 1 i
h e
l-9111260261o$00$$-
411,
^
ng TABLE 2.2.-1
^'
REACTOR TRIP SYSTEM INSTRlMENTATION TRIP SEIPOINTS
\\,
TOTAL SENSOR
\\
^
E ALLOWANCE ERROR Y
3 FUi4CT10NAL UNIT
[TA)
Z (S)
TRIP SEIPOINT Att0WABLE VALUE l
s 1.
Manual Reactor Trip N.A.
N.A.
N.A.
N.A.
N.A.
l 2.
Power Range, Neutro..% ux a.
High Setpoint
- 7. 5 5.92 0
1109% of RIP
- 1110.9% of RTP*
b.
Low Setpoint 8.3 5.92 0
$25% of RTP"
$27.1% of RTP*
i 3.
Power Range, Heutron Flux,
- 1. 6 0.5 0
$5% of RTP" with
$6.3% of RTP* with l
High Positive Rate a time constant a time constant i
-. 2 seconds
> 2 seconds.
4.
Power Range, Neutron Flux,
' 1. 6 0.5 0
15% of RTP* with
$6.3% of RIP
- with High Negative Rate a time constar.t a time constant 32 seconds 32 seconds 1
5.
Intermediate Range, 17.0 8.4 0
(25% of RTP*
<31% of RIP
- Neutron Flux i
6.
Source Range, Neutron Flux 17.0 10 0
$105 cps
$1.4 x 10 cps 5
7.
Overtemperature AT L6eS81 IMl lJef21 See Note 1 See Note 2
[1.7 8.
Overpower AT 4, 9 1.24 See Note 3 See Note 4 y
9.
Pressurizer Pressure-tow 4.0 2.21 1.5 31945 psig 31938 psig***
10.
Pressurizer Pressure-High
- 7. 5 0.71 0.5
$2385 psig
$2399 psig ua 11.
Pressurizer Water Level-High 5.0 2.18 1.5
<92% of instrument <93.8% of instrument
{[
span span
??
12.
Reactor Coolant Flow-Low 2.92 1.48 0.6
~
>90% of loop 388.9% of loop f
ininimum measured minimum measured flow"*
mm A4B M Wir 14 3 0 ret U.J r 1 4 80
- 2. s 2. foa des er-I ggowna o cn 22 6.9 @
er 2-7.2_. Fog drbr 2.
A.ao 2.7 rat d.J er 2.
oa ta?
- RTP = RATED THERMAL-POWER
- Loop minimum measured flow = 96,900 gpa (Unit 2), 96,250.gpa (Unit 1) ws"" *** Time constants utilized in the lead-lag controller for Pressurizer Pre: sure-t ow are 2 seconds for lead and I second for lag.
Channel calibratiori stiali esistare that triese time coristasits ase adjonsted to these values.
i
k TABLE 2.2-1 (Continued)
~
TABLE NOTATIONS (Continued) gi s
7 N0iE 1:
(Continued)
T'
$ 590.8'F (flominal T,yg allowed by Safety Analysis);
d 0.001189; K
=
3 g
Pressurizer pressure, psig;
[
P
=
2235 psig (Nominal RCS operating pressure);
P'
=
Laplace transfora operator, s 8; j
5
=
and f (AI) is a function of the indicated difference between top and bottom detectors of the 3
power-range neutron ion chambers; with gains to be selected based on measured instrument response during plant STARIUP tests such that:
y (1)
For q g between -22.5% and -6.5%,
g b
f (61) = 0, where qt and q are percent RATED TiiERMAL POWER in the top and bottom b
halves of the core respectively, and q
+g is total TilERMAL POWER in percent of b
NATED TilERMAL POWER; (11)
For each percent that the magnitude of q q
is a re negative than -22.5%, the b
((
AT Trip Setpoint shall be automatically reduced by 3.151% of its value at RATED yy TifERMAL POWER; and Is # r positive than -6.5%, the AT. Trip ae SS (iii)
For each percent that the magnitude of qt qb ff Setpoint shall be automatically reduced by of /ts value at. RATED lilERMAL POWER.
ll.64f % 4e oder i 1.4t+ % r.e od e 2 l o,.
The channel's maximum Trip Setpoint "shall not exceed its computed Trip Setpoint by I
c2 m NOTE 2:
en EE more thart t 3 % ree ode 4 l l 3.07, M od.r I asc>
g
l 4
l i
+
D F
)
1 i
i 4
I'.
i Attachment III l-e I
y.
2 k
?
l.
W t
4 P_roposed Revisi_op to Technical Specification Table 2.2-1 This proposed Tecanical Specification revision changes the slope value for the positive wing of the axial offset band, which was determined to be potentially nonconservative for Catawba Unit 2, such that it will conservatively provide the necessary margin to DNB.
In addition, the unit specific values for Total Allowance, Z,
S and Allowable Value are added since a now, more restrictive, Allowable Value was calculated for Unit 2.
Technical Justification The overtemperature AT (OTAT) reactor trip is designed to protect the reactor core from DNB over a range of temperatures and pressures.
The setpoint for the OTAT trip is variable depending upon RCS temperature, pressurizer
- pressure, and axial flux difference.
Due to a potential nonconservatism discovered in the methodology used to calculate _the F-Delta I (f(AI)) reset portion of the OTAT trip function, it was determined that the positive side of the axial offset band was non-conservative for Catawba Unit 2.
The f(AI) reset portion of the trip function is designed to lower the trip setpoint when axial flux dif ferences exceed predetermined i
l limits.
Since the limiting margins to DNB occur as the result of highly skewed power distributions, a slope change to the positive wing on the axial offset band is necessary in order to prevent the DNB limits from being exceeded.
Therefore, an evaluation was performed using the Improved Thermal Design Procedure to determine a new value for the slope of the positive side of the axial offset l
band which conservatively bounds this operating region.
This new l
slope value will be included as a Catawba Unit 2 specific value in the Technical Specifications.
For Catawba Unit 2, Westinghouse calculates the OTAT f(AI) reset function, which is presented in the Technical Specifications, based on axial offset limits and core thermal limits.
The current methodology, the Improved Thermal Design Procedure, uses a linear extrapolation beyond 118%
power to generate the f(AI) reset function.
However, since (depending on the DNB correlation used) the axial offset limits are not independent of power (the deadband and slope of an 118% power curve are not similar to those of an 80%
power curve), that calculation may be non-conservative for some plants.
Specifically, the calculated slope of the positive wing of the f(AI) reset function may not be as high as it would be if calculations were performed using actual axial offset limit data at the higher power levels (the negative wing is not adversely affected because of the typically large negative AI band and since the axial power shapes with negative axial offsets are typically l
not limiting),
t j.
Since the positive wing slope provides the gain values for the f(AI) setpoint penalty, an uncertainty in this penalty would be multiplied by this gain to translate it into an uncertainty in the
_.____m..-
K, term of' the OTAT setpoint. Therefore, the change in the positive wing of - the axial offset band necessitates a change to the Allowable Value and Z value for Catawba Unit 2.
Also included in the Z value change is an increase in the uncertainty associated with the incore flux map accuracy.
The previous value used for this uncertainty was 11.2%AI span; however, as a result of recent re-calculations the now value for this uncertainty was determined to be slightly higher at 11.3%AI span.
This now flux map accuracy uncertainty of 1.3%AI span has been included in Z along with the change rouulting from the increased positive wing slopo of the c.xial ofiset band.
A now, more restrictive, Allowable Value was calculated as a result of the change in the positive axial offset wing slope.- The Total Allowance, Z and S values are also changed as the result cf the uso of Westinghouse methodology, which includes the Al '.ncertainties in the K t.orm of the OTAT setpoint i
as opposed to leaving the uncertainty allowances out of K and using i
them to adjust the f(AI) trip reset function breakpoints.
Therefore, the Total Allowance, Z,
S and Allcwable Value are to be l.
given as unit specific values to replace the dual unit values in the current Technical Specifications.
In summary, the Technical Specification changes described above are required to ensure adequate DNB protection for the Catawba Unit 2 reactor core during plant operation.
These changes are Catawba Unit 2 specific and do not affect the values for Unit 1 since the uncertainty _ allowances for :' nit 1 were determined using an approved non-Westinghouse methodology.
i l
.s
G 4
s Attachment IV s
e
l NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT
]
CFR 50.92 states that a
proposed amendmr'nt involves no significant hazards consideration if operation in accordunce with the amendment would not:
1)
Involve a
significant increano in the probability or consequences of an accider.t previously evaluated; or 2)
Create the possibility of a new or different kind of accident from any accident previously evaluated; or 3)
Involve a significant reduction in a margin of safety.
This proposed Technical Specification revision chcnges the slope value for the positive wing of the axial offset band, which was determined to be nonconservative for Catawba Unit 2, such that it will conservatively provide the necessary margin to Dt1B.
In addition, the unit spccific values for Total Allowance, Z,
S, and Allowable Value were calculated for Catawba Unit 2.
These proposed changes to the Technical Specifications do not involve a significant increase in the probability or consequences of an accident previously evaluated.
Due to a
potential nonconservatism discovered in the methodology used to calculate the f(31) reset portion of the OTAT trip function, it was determined that the positive side of the axial offset band was non-conservative for Catawba Unit 2.
The f(31) reset portion of the trip function in designed to lower the trip setpoint when axial flux differences exceed predetermined limits.
Since the limiting margins to DNB occur as the result of highly skewed power distributions, a s] ope change to the positive wing on the axial offset band is necessary in order to prevent the DNB limits from being exceeded.
Therefore, an evaluation was performed to determine a new value for the slope of the positive side of the o
axial offset band which conservatively bounds this operating region.
Since this change ensures that the DNB limits are not exceeded the probability or consequences of an accident previousl evaluated are not increased.
The changes to the Z and Allowable Value reflect the change in the positive wing of the axial offoot band.
As discussed in the Technical Justification, included in the Z value is an increase in the uncertainty associated witn flux map accuracy.
The Total Allowance, Z,
and S values also change as a result of using Westinghouse Methodology to calculate the values instead of Duke methodology which was used to calculate the current values.
Since these changes ensure that DNB limits ar e not exceeded, and systems used to mitigate an accident are not affected, the probability or consequences of an accident pceviously evaluated are not increased.
As discussed above the proposed changes to the Technical
4 4
Specifications are being made to ensure that DilB limits are not exceeded.
Because this change conservatively ensures that Dt1B limits are not exceeded, and because the operation of other plant systems are not
- affected, this change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
As discussed in the Technical Justification it has been determined that the positive side of the axial offset band was non-conservative for Catawba Unit _.
This change ensures that the non-conservatism in the Westinghouse Methodology is accounted for, therefore increasing the margin of safety.
Environmental Impact Statement The proposed Technical Specification change has been reviewed against the criteria of 10 CFR 51.22 for environmental considerations.
As shown above, the proposed change does not involve any significant hazards consideration, nor increase the types and amounts of effluents that may be released offsite, nor increase the individual or cumulative occupational radiation exposures.
Based on this, the proposed Technical Specification change meets the criteria given in 10 CFR 51.22 (c)
(9) for categorical exclusion from the requirement for an Environmental Impact Statement.
l
___.___ _ __._