ML19341A172
| ML19341A172 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 01/13/1981 |
| From: | PORTLAND GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML19260G481 | List: |
| References | |
| TAC-42281, TAC-43444, NUDOCS 8101220274 | |
| Download: ML19341A172 (8) | |
Text
-
" " " 2) o WES3GHCYSE C ASS 3 TROJ.C CYCLE 3 IMPROVED BOL, HZ?, PCWER DI5*".C3CION PREDICTION Trojan Cycle 3 startup physics tests results indicated larger than expected e
differences between measured and predicted power distributions at 30L, EZP conditions.
These differences have been evaluated by Westinghouse and the results of the evaluation have indicated [
] contributing factors not included in the design predictions which account for a significant part of the difference between =easurenent and prediction.
[
] factors
\\
are l l
1 l
I The attached figures are a comparison of percent differences between "4
measured and predicted assembly powers at 30L, ARO, HZP conditions (MA? 79) i for 1) predictions based on the design model, and 2) predictions based on a model which incorporates the effects of the aforementioned [
] factors.
The comparison of measured versus design model predicted assembly powers is shown in Figure 1.
A similar comparison based on the improved predictions is shown in Figure 2.
Significant improvenent is noted in Figure 2 where i
differences between measured and predicted powers near the [
] of the l
(
core are now within [ ] percent.
The effects are quantitatively esti=ated l
to improve the power by:
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-H C/3 L1J Trojan Cycle 3 Percent Di ference between Measured and Design Predicted
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ENCLOSURE (4)
WiS" AGnC,Si C. ASS a CHANGES TO IMPROVE CYCLE 4 PREDICTIONS Per request of Pot land General Electric, additional information related to the improved Trojan Cycle 3 BOL, ARO, HZP power distribution is provided as follows:
- 1) The revised 30L, ARO, HZP boren concentration is [
]
This a,e value is composed of a calculated [
] boren concentration of [
] ppm which includes the effects of power coastdown in Cycle 2 on peak (samarium] and the effects of measured assembly burnups.
In addition ai
] correction of [
] ppa is added to account for the additional
[
] power distribution effects. This value was determined by comparison of [
] boron concentration calculations with equivalent mesh [
] calculations.
- 2) The measured quadrant pcwer asymmetry at BOL, ARO, EZP based on the revised INCORE constants is:
- a,c i
i
?
]
- 3) The improved BOL, HZP power distribution showed an improvement of up to a,e j
[
]% in the [
] of the core.
In previous E evaluation of l
Cycle 3 startup results, it was estimated that incorporation of the [
]
l effects, measured burnups, and power coastdown effects on peak [ samarium] l M
eo
- j T }lni o D
o Ju. 2. k do i
WESTAGn0lSE C. ASS 3 would result in only a [ ]
i=provement.
The additional i=provement in the a,c revised calculation is a result of the method employed to include.[
] effects in the [
] power distri bution prediction required for DCORE constant generation.
The [ ]% improvement was a conservative estimate based on a summation of the effects of measured [
], improved peak
[
] treatment, and [
] effects which were derived from comparison of changes in power distribution from HFP to HZP conditions in [
] and equivalent mesh [
] calculations.
Incorporation of these effects into UCORE by this method would require [
] modification of UCORE results to include
[
] effects.
Instead, a method was available which incorporates [
] effects into a [
j calculated [
] treatment which was then employed in the [
] model to generate constants for UCORE.
The use of this procedura produced better results than originally estimated.
- 4) With respect to Cycle 4 startup predictions, the following changes are a,e planned to be included at this time:
a)
[
j assembly burnup data from Cycle 3 will be used.
b)
The method of (
] as.smblies from all (
j quadrants in Cycle 3 will be employed in the Cycle 4 loading pattern to
(
) quadrant [
] based on latest available seasured burnup data.
c)
[
] effects will be accounted for in 1) borou concentration ii)
HZP power distribution Improved [
! treatment based on [
l calculations will be used.
l O
WES1XGE0LSi CMSS 3 d)
To the extent that information on Cycle 3 is available, Cycle 3 a,e power coastdown effects on [
] in Cycle 4 will be accounted for.
4 Additional work is planned in the area of improved power distribution predictions, and any new techniques available at the time that Cycle 4 predictions are being generated will be considered for applicstion to Trojan Cycle 4.
i 1
l
ENCLOSURE (5)
TROJAN SHUTDOWN M*RCLL CTCt! 3 The attached table sinmanizes nuclear design informeion for the Trojan Nuclear Plant cycle 3 startup that Portland General Electric received from Westinghouse. The total reactivity control requirement, including technical specifications requirements for steam break was calculated to be 4.11 h and 5.04 2 &t ML and EOL respectively. The available worth of all the control rods minus the single most reactive rod including a 10% allowance for nuclear calculational uncertainty is 4.87h and 5.29L'o at BOL and EOL respectively. This translates into an excess shutdown margin of 0.766 and 0.256 respectively at BOL and EOL.
The Trojan cycle 3 physics startup tests measured a RZP, ARO critical baron concentration of 1452 ppa. The RZP, critical boron concentration with all rods in, except for one rod, was measured to be 886 ppa. Hence.
the measured borou equivalent worth of the reactivity control available is l
1452 ppa - 886 pga = 566 pga.
The comparable prediction was 605 ppa for all rods in less K8, the most reactive rod. Thus, the'amasurement was lov by about 6.4%.
Although the conservativs 10% rod worth allowance includes the measurement error, even if the ARO and ARI-1 boron measurements were both in error by 5 ppa in the conservative direction, the measurements would then be low by about 8%.
It can be seen that the measurement data still vill fall comfortably within the 10% less worth allowance that the designer used in developing the design available shutdown margins of 2.36 h and 1.85 m. Since the av'ailable shutdown margins are required f
to be at least 1.6 2, the identified margins are adequate and an excess margin exists.
It should be noted thac even more shutdown margin techni-cally exists due to the excessive reactivity control allocuent of 0.50:Ac assigned to the rod insertion allowance in the Table. The rod insertion limit at Trojan is 189 steps at full power; at that condition the rod insertion allowance should be closer to 0.25%as.
e 3
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ENCLOSURE (5)
TROJAN NUCLEAR PLANT CYCLE 3 SHUTDOWN MARGIN Reactivity Requirement BOL Worth (tae)
EOL Worth ("Ao)
Doppler 1.10 1.01 Rod Insertion Allowance 0.50 0.50 Variable TMcD 0.41 0.98 Redistribution 0.50 0.95 2.51 3.4A Steam Break Tech. Specs L 60 1.60 Total Requiremenc 4.11 5.04 Availabiliev Requirement Worth (tae)
Vorth less 101 BOL, H:?,
5.41 4.87 All rods in - 1 rod EOL, HZP 5.88 5.29 All rods in - 1 rod Design Available Margin BOL :.a 4.87 - 2.51 = 2.36 EOL Zao 5.29 - 3.44 = 1.35 BOL (%as)
EOL (%4c) l i
Excess Shutdown Margin 4.87 - 4.11 =
5.29 - 5.04 =
Beyond Required Margin l
Iseluding Tech Spec 0.76 0.25 Requirements f
l l
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