ML19276F783
| ML19276F783 | |
| Person / Time | |
|---|---|
| Issue date: | 03/26/1979 |
| From: | Hodges M Office of Nuclear Reactor Regulation |
| To: | Rosztoczy Z Office of Nuclear Reactor Regulation |
| References | |
| 790320, NUDOCS 7904120096 | |
| Download: ML19276F783 (15) | |
Text
.
ch UNITED STATES Oh 4
NUCLEAR REGULATORY COMMISSION jy~ M. j WASHINGTON, D. C. 20655
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MEMORANDUM FOR:
Z. R. Rosztoczy, Chief Analysis Branch, DSS THRU:
L. E. Phillips, Section Leader, Reactor Analysis Section, Analysis Branch, DSS j 7J;( p g69 FROM:
M. W. Hodges, Reactor Analysis Section, Analysis Branch, DSS
SUBJECT:
SUMMARY
OF MEETING WITH EXXON A meeting was held on March 12, 1979, with representatives of Exxon Nuclear Corporation, to discuss the new data base for the XN-2 CHF correlation.
Copies of the slides presented at the meeting and a list of attendees are enclosed.
The Exxon presentation discussed plans for a new procedure for calculating mininum critical power ratio (MCPR) safety limits and sumarized the new data base for the XN-2 CHF correlation.
The new procedure for calculating MCPR limits will involve a statistical combination of monitoring uncertainties in which errors are propagated by a Monte Carlo method and probabilities of rods in boiling transition are sumed for the reactor core for each Monte Carlo trial. A topical report describing this procedure is to be submitted by early fall. The staff cautioned Exxon that the procedure should include identifiable margin as insurance against potential reduction of calculated safety margin due to problems which are unanticipated at the time of core design.
The XN-2 CHF correlation calculates critical assembly power from asserrbly average fluid conditions. The XN-2 was developed from data on 6 foot length heated rods with uniform axial heat flux. The Tong factor was adopted for use with non-uniform axial power distribution.
The new expanded data base shows that the XN-2 is applicable to full length heated rods and to non-uniform axial power distributions.
Exxon plans to submit a topical report on the XN-2 within about 30 days.
They requested an expeditious review because the outcome of that review will impact their core design procedure. To facilitate a rapid review, Exxon provided a draft copy of the report to the staff in December,1978 and several discussions of required modifications have been held between Exxon and the staff.
The 7904120ON
Z. R. Rosztoczy staff has also contracted for Georgia Tech. to compare the correlation to the data base and that work is in progress. Because of Exxon's coopera-tion in the early stages of this review, the review can probably be completed by late sumer.
Wayne Hodges Analysis Branch Division of Systems Safety cc:
R. Mattson R. Tedesco a ing Attendees PDR
Meetino with Exxon on March 12, 1979 Wayne Hodges NRC/ DSS /AB Stuart Rubin NRC/ DOR /RSB Frank Coffman NRC/ DOR /RSB T. W. Patten ENC - T.H.E.
C. E. Leach ENC - T.H.E.
Thomas L. Krysinski ENC - T.H.E.
John White ENC - Licensing Gary Holahan NRC/ DSS /AB Andrew Hon NRC/RES Brian Sheron NRC/ DSS /AB George Sofer ENC Mike McCoy NRC/ DSS /AB Larry Phillips
- NRC/ DSS /AB
- Part-time
GENERATION OF REACTOR MCPR SAFETY AND OPERATIONAL LIMITS MCPR SAFETY LIMIT PROTECTS 99.9% OF RODS IN REACTOR CORE.
MCPR SAFETY LIMIT DEFENDS UPON POWER MONITORING STRATEGY, MEASUREMENT UNCERTAINTIES AND CRITICAL POWER CORRELATION.
CRITICAL POWER OPERATIONAL POWER MONITORING CORRELATION UNCERTAINTIES STRATEGY STATISTICAL
~
COMBINATION V
MCPR SAFETY LIMIT MCPR SAFETY LIMIT + aMCPR DUE TO TRANSIENT ANALYSIS =
OPERATIONAL LIMIT.
STATISTICAL COMBINATION OF MONITORING UNCERTAINTIES ERRORS ARE PROPAGATED BY MONTE CARLO METHOD.
INDEPENDENT VARIABLES OF CPR MONITORING STRATEGY ARE ALLOWED TO DEVIATE ACCORDING TO APPROPRIATE FREQUENCY DISTRIBUTIONS.
PROBABILITIES OF RODS IN BT ARE SUMMED FOR REACTOR CORE FOR EACH MONTE CARLO TRIAL.
DISTRIBUTION OF THE RESULTS OF ALL MONTE CARLO TRI ALS IS ANALYZED TO YIELD MCPR SAFETY LIMIT.
-e
XN-2 CRITICAL POWER CORRELATION
~
CALCULATES CRITICAL ASSEMBLY POWER FROM ASSEMBLY AVERAGE FLUID CONDITIONS COMPARES HOT ROD HEAT FLUX TO CRITICAL HEAT FLUX TONG FACTOR FOR NONUNIFORM AXIAL POWER DISTRIBUTION ITERATIVE SOLUTION FOR CRITICAL POWER SUPPORTED BY DATA BASE OF 574 TEST POINTS MODEL CPR PREDICTION AS NORMAL DISTRIBUTION
XN-2 DATA BASE MAX.
ilUMBER LENGTH AXIAL LOCAL DATA TEST GROUP FT.
PROFILE PEAKING H,IN.
POINTS ENC-I A1, A2, B1 7
UNIFORM 1.28 0.525 82 B2, C1, C1, E 7
UNIFORM 1.28 0.525 146 D
7 UNIFORM 1.25 0.525 23 HB 6.5 UNIFORM 1.20 0.531 35 ENC-II 12 C0stse 1.22 0.472 90 (1.50 MAX)
ENC-III 12 U SINE U 1.24 0.472 78 (1.47 MAX)
CISE B
12 UNIFORM 1.02 0.524 30 C,D,E,F 12 UNIFORM 1.20 0.524 74 G
12 UNIFORM 1.26 0.524 16 TOTAL 6.5-12 UNIFORM &
1.02-0.472-574 NONUNIFORM 1.28
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LOCAL PEAKING CONFIGURATIONS IN Xil-2 DATA BASE ENC-I TEST SECTIONS r
3 r
3 1.20 1.00 1.20 1.00 1.02 1.28 1.10 0.88 1.00 1.10 1.10 1.20 1.28 1.00 0.88 1.00 1.00 0.60 0.89 1.20 1.00 0.53 0.88 1.00 1.10 0.89 0.52 1.00 1.07 0.89 1.00 1.19
(
(
TEST SECTION HB TEST SECTIONS A1, A2, & B1 fiAx F
= 1.20 max F
= 1.28 L
L F ' = 1.048 F ' = 1. 043 L
L
(
)
r 3
1.03 1.28 1.09 0.92 1.01 1.06 1.07 0.90 s
1.01\\0.90 1.28 1.03 0.92 1.00 1.06 0.98 1.00 0.53 0.88 0.99 '
O.98 1.25 0.86 0.97 (0.99 1.07 0.88 1.19 1.04 0.87 0.97 1.06 L
j TEST SE:TIONS B2, C1, C2 & E TEST SECTION D iiAX F
" 1.28 MAX F
= 1.25 L
L F '=.1.049 F '= 0.995 L
L
LOCAL PEAKING CONFIGURATIONS IN XN-2 DATA BASE (CONT.)
r
~
a r
3 1.06 1.06 1.22 1.06 1.04 1.04 1.24 1.04 0.84 0.84 1.06 1.22 0.89 0.89 1.05 1.23 0.84 0.84 0.84 1.06 0.89 1.04 0.89 1.04 0.84 1.06 1.06 1.06 0.89 0.89 0.89 1.03
(
(
-~iTSECTkONENC-II TEST SECTION ENC-III TE max F
= 1.22 MAX FL = 1,24 L
F ' = 1. 036 F '= 1.039 L
L r
3 r
3 1,20 ) 0.93, 1.02 1.00 1.00 1.02 0.9 (1.20 )
j
~ J' 1.00 1.00 1.00 1.00 0~. 93 0.93 0.93 0.93 1.00 1.00 1.00 '
O.93 0.93 0.93 0.93 v
( '
1.02
.1.02 1.00 1.20 0.93 0.93 1.20 t
)
CISE TEST SECTION B CISE TEST SECTION C MAX FL = 1.02 MAX F
= 1.20 L
F ' = -1. 00 F '= 1.00 L
L
LOCAL PEAKING CONFIGURATIONS Ill XN-2 DATA 3AsE (CONT.)
F 3
(
3 0.93 0.93 1.20 0.93 0.94 0.94 0.93 0.94 0.93 0.93 0.93 1.20 0.94 1.20 0.93 0.93 0.93 0.93 0.93 0.93 1.20 1.20 0.93 0.93 1.20 1.20 0.93 0.94 0.93 0.94 0.94 N
^ ^ ~
^
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CISE Test SECTI0r4 D CISE Test SECTION E MAX F
= 1.20 MAX F
= 1.20 L
L F(=1.01 Fg=1.02 r
3 r
3 0.94 0.93 0.93 0.94 0.99
.97 0.97 0.99 0.94 0.94 0.93 0.99 1.00 1.00 0.97 1.20 1.20 0.93 0.93 1.26 0.37 0.97 0.97 1.19 1.20 0.94 0.94 1.25 1.26 1.00 0.99 L
CISE TEST SECTION F CISE Test SECTION G MAX FL = 1.20 max F
= 1.26 L
F[=1.09 F '= 0.99 L
e m-
- *w h-,,%e, STATISTICAL APPLICATION OF Xii-j2 OvERALL WEIGHTED MEAN DETERMINED FROM MEANs VARIANCE AND NUMBER OF DATA POINTS FOR EACH TEST GROUP.
OVERALL STANDARD DEVIATION INCLUDES WITHIN-GROUP AND BETWEEN-GROUP CONTRIBUTIONS.
OVERALL MEAN = 1.0024.
OVERALL STANDARD DEVIATION = 0.0448.
EXPERIENCED FEWER BTS IN " TAILS" THAN FITTED NORMAL DISTRIBUTION.
30 i
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XN-2 PREDICTIONS 70 NORMAL DISTRIBUTION 60 7
S O 50
/5 d
\\
$C C5g 40 g
5g
\\
Q 30 e
$s=
2C 10 q
n
- 0. 10 n.35 0.90 0.95 1.0 1.05 1.10 1715 1.20 CPR GROUP
SUMMARY
OF XN-2 CORRELATION CPR PREDICTED AS NORMAL DISTRIBUTION.
FULL LENGTH NONUNIFORM AXIAL DATA PRE-DICTED WELL.
PROTOTYPIC LOCAL PEAKING DISTRIBUTIONS FOR UNCONTROLLED ASSEMBLIES ARE INCLUDED IN DATA BASE.
XN-2 IS CONSERVATIVE FOR TRANSIENTS.
XN-2 DATA BASE FOR TRANSIENT OPERATING CONDITIONS TWENTY-ONE (21) TRANSIENT DATA POINTS.
FULL LENGTH ASSEMBLY WITH U SINE U AXIAL PROFILE.
POWER INCREASE.
FLOW DECAY.
LOCA POWER AND FLOW DECAY.
XN-2 CONSISTENTLY UNDERPREDICTS THE TIME To BT.
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