ML19345E493
| ML19345E493 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/31/1977 |
| From: | Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Desiree Davis Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8102040677 | |
| Download: ML19345E493 (11) | |
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> ConSum8f8 L power Company Gehecal OM ces: 212 West Micnigan Avenue, Jackson ocnegen 49:01 e Area Code S17 788-OSEO
'i Aschst 31,~1977 sf YMT/(
Mik st-Director of Nuclear Reactor Regulation Att: Mr Den K Davis, Acting Branch Chief Operatir.s Reactor Branch No 2 US Nuclear Regulatory Co==ission Washington, DC 20555 j
DOCKET 50-155 - LICENSE DFR BIG ROCK FOINT "LAUT -
CFAIIGE III MCHFR LIMITS Enclosed is an Exxon Nuclear Corporation study which provides a synthesiced Hench-Levy Minimum Critical Heat Flux Ratio (MCEFR) limit which ensures that a Minimum Critical Pcver Ratio (MCFR) limit cf 1.32, as derived by the X'i-2 Critical Fover Correlation, vill net be violated at Big Rock Point. This ctudy is forverded in response to your letter of August 3,1977
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David A Bixel Nuclear Licens'.ng A inistrator CC: JGKeppler, USHRC a
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HENCH-LEVY MCHFR LIMIT FOR THE BIG ROCK POINT REACTOR SUFMARY Jg
?- A minimum critical heat flux ratio (MCIFR) limit of 2.15 as determined by M
th4 ENC synthesized Hench-Levy critice] *1 eat flux correlation has been shown to be conservative in the assessment of thermal margins i'or the Big Rock Poirt-Reactor. The 2.15 MCHFR limit was determined to conservatively provide nonpene-tration of the 1.32 minimum critical-power ratio (MCPR) as determined by the XN-2 critical power correlation.
The analysis, performed with the XCOBRA computer
- code, considered the effects of variations in power / flow, essen.bly local peaking, axial power distribution and nominal expected conditions. The 2.15 MCHFR limit was deter =ined to be applicable for the limiting assembly and envelopes the anticipated operating rar.ge of axial power distribution, inlet enthalpy, local peaking, and mass velocity for " ele 15 ar.a future cycles.
f The 2.15 MCHFR limit ye shown to be' applicable for conditions of reduced reactor flow as long as the nominal power-to-flow relationship is mainta'.ned;
'that is the MCPR was determined to be greater for the partial power / partial flow cases than the full power / full flow case.
The analysis assumes that the l
reactor is operated such that a reduction of reactor flow is accompanied by a proportionate reduction in reactor power.
THERMAL HYDRAULIC ANALYSIS The analysis presented here is necessitated by the desire to relate the
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)D{ as determined by the ENC synthesized Hench-Levy critical heat flux correlation with the MCPR as determined by the NRC approved XN-2 critical power
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correlation. The analysis consists of several sensitivity studies which estab-lish an MCHFR limit that conservatively provides nonpenetration of the 1.32 XN-2 MCPR limit.
.f' A power-flow sensitivity was performed to determine the most limiting con-dNons for Cycle 15 and subsequent cycles in terms of full pcwer/ full flow or
%I partf al power / partial flow at the reactor operating design conditions shown in Table 1.
As shown in Table 2, the most limiting condition was determined to be full power / full flow. The additional sensitivity studies were then per-formed at conditions equivalent to those given in Table 1 to establish the required Fench-Levy MCHFR limit value which envelopes anticipated operating conditions for Cycle 15 and subsequent cycles.
An assembly local peaking sensitivity study was performed assu=ing the most adverse anticipated conditions af assembly local peaking and asse=b"ly axial t
power distribution as well as 50% variation in inlet subcooling enthalpy.
For each value of inlet enthalpy and mass velocity, those fuel assembly powers which resulted in an XN-2 MCPR of 1.32 were determined. The Hench-Levy MCHFR for each case was then calculated using the conditions obtained above. As is shown in Table 3, the maximum Hench-Levy MCHFR so obtained was 2.11.
Thus, for additional conservatism a Hench-Levy MCHFR limit value of 2.15 is proposed.
The sensitivity of the Hench-Levy MChTR limit to axial pmr distribution was determined in this study. This se. sitivity is shown by comparison of the local peaking sensitivity results (Table 3) with the results of a similar set o'f calculations which assumed an axial peaking of 1 5 at X/L = 0 5 All other l
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aIppembly conditions were identical to those used in the local peaking sensitivity st,udy.
The determination of the MCPR limiting assembly power and corresponding -
Hench-Lery MCHFR values was identical to the procedure used in th_e local
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. peaking study.
As shown in Table k, the highest Hench-Levy so obtained was 2.06 and j
further illustrates that the proposed value of 2.15 conservatively envelopes anticipated Cycle 15 and subsequent cycle conditions.
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~i The nominal expected conditions study was performed to assess the con-
.L Efvatism of a 2.15 ENC synthesized Hench-Levy MCHFR limit at the conditions indicated in Table 1.
An ENC synthesized Hench-Levy MCHFR limit of 1.60 was found to be adequate, further demonstrating the acceptability of the proposed
-2.15 limit. The results of this sensitivity study are shown in Table 5.
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4 T3EE 1 ASSUMED OPERATING CONDITIONS Reastor Power 8122% Overpower, W 'h 292.8 t
1k Ef96ctive' Reactor Flow Rate, 10 lb/hr 99 i
. Inlet Subcooling, Btu /lb 22.8 t
Opere.4 4.ng Pressure, psia 1350 Hot Assembly Opere. ting Conditions
- Hot Assembly Flow Rate, lb/hr 123,100 Radial Feaking 1.h5 a,
Local Peaking 1.20 Assembly Power 8122% Overpower, W 5 05
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SENSITIVITY OF THERMAL MARGINS
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TO PARTIAL POWER / FLOW. OPERATION Hot ' Assenhly Theraal Dic. gin Reactor Power Effective Reactor ENC-Hench-Levy-
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Percent of Rated Power / Flow th 6
122/100 292.8 9.9 x 10 1.86 1 52 6
100/100 240-9 9 x 10 2.63 1.87 6
75/75 180 7.4 x 10 3 55 2.25 6
50/50 120 5 0 x 10 5.40 2.80 i
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SENSITIVITY OF THERMAL MARGINS
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Assembly Mass Velocity-(1b/hr-Assembly Flow Inlet Enthalpy Assembly Power Hench-Levy XN-2
'ft2)
(1b/hr)-
(Btu /lb)
(MW)
'560 3.66 2.00 1.32 6~
0 91 x 10 148,600 570 3 57 2.03 1.32 6
1.12 x 10 182,800
.580 3.40 2.11 1.32-4 d
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1 70 axial peak @ 0 7 of core height.
1.60 local peaking factor.
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TABLE 4-
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,f SENSITIVITY OF THERMAL MARGINS TO m ** - r ASSBfBLY AXIAL PEAKING CONDITIONS 1
Assem'.,.y Mass XN-2 Velocity (1b/hr-Assembly Flow Inlet Enthalpy Assembly Power Hench-Levy' MCPR ft2)
(1b/hr)
(Btu /lb)
(MW)
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. 0 79 x 10 127,900 560 k.22 1 94 1.32 6
0.91 x 10 148,600 570 4.10 1.97 1.32 6
1.12 x 10 182,800 580 3.88 2.06 1.32 T
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2 151 axial peaking 8 0 5 of core height.
. 1.60 local peaking factor.
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l'ABIA 5 SENSITIVITY OF THERMAL MARGINS AT NOMINAL ASSEMBLY CONDITIONS t
Assembly Mass Peak Assembly Inlet Enthalpy Hench-Levy XN-2'
()y* locity b/hr-ft2)
Flow (1b/hr)
(Btu /lb)
MCHFR*
MCPR*
0.65 x 1 106,200 560 1.60 1.h5 0.70 x 10 11k,h00 570 1.60 1.h7
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0 77 x 10 124,700-580 1.60 1.h8 i
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'Carresponding to reactor operation at 122% overpower as shown in Table 1.
1.51'axisl peaking at.5 of core height.
f 1.20 local peaking factor.
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e REFERENCES 1.
XN-75-3h, "The XN-2 Critical Power Correlation," Revision 1 (1975).
2.
XN-NF-77-43, "XCOBRA Code Operating Manual" (1977).
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NRO DISTRIBUTION na PART 50 DOCKET MATERIAL l
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FROM: Consumers. Power Co.
D*TE C' 00C#8NT l
l Mr. Don K. Davis Jackson, Michigin 49201 08/31/77 a
i David A. Bixel DA7gggtlgo e
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ENCLOSU RE Consists of Exxon Nuc. Corp. study si providing synthesized 11ench-Levy Minimum Critical IIcat Flux Ratio limit.
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