ML20082A639

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Review of Technical Issues Related to Long Term Solution I-D 'Regional Exclusion w/Flow-Biased APRM Scram.'
ML20082A639
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 09/30/1994
From: Marchleuba J
OAK RIDGE NATIONAL LABORATORY
To:
Office of Nuclear Reactor Regulation
Shared Package
ML20082A345 List:
References
CON-FIN-L-1697 ORNL-NRC-LTR-93, ORNL-NRC-LTR-9323, NUDOCS 9504040165
Download: ML20082A639 (18)
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.

N ORNL/NRC/LTR-93/23 Contract Program: Technical Support for the Reactor Systems Branch ,

(L1697/P2)

J l

Subject of Document: Review of Technical Issues Related to Long Term Solution

- I-D " Regional Exclusion with Flow-Blased APRM Scram" l

Type of Document: Technical Evaluation Report Author: Josd March-12uba Date of Document: September 1994 l

NRC Monitor: T. L. Huang, Office of Nuclear Reactor Regulation l

l Prepared for U.S. Nuclear Regulatory Commission ,

Office of Nuclear Reactor Regulation I under i DOE Interagency Agreement 1886-8169-7A l NRC JCN No. L1697, Project 2, Tasks 11 & 12 l l

Pmpared by Instrumentation and Controls Division OAK RIDGE NATIONAL LABORATORY managed by MARTIN MARIETTA ENERGY SYSTEMS, INC.

for the U.S. DEPARTMENT OF ENERGY under Contract No. DE-AC05-840R21400 9504040165 950331 ENCLOSURE 2 i PDR ADOCK 05000271 '

P PDR l

  • . l l

S13 DIARY  ;

This report documents our review of Option I-D for long term solution of the boiling water reactor (BWR) stability issue. The main conclusion from this review is that Option I D, as l described in the licensing topical report NEDO-31960' and its supplement 1,2 is conceptually '

an acceptable long term solution for small-core plants with tight core inlet restriction and unfiltered flow-biased scram. A number of issues, however, have not been completely resolved yet by the utilities involved in this option, and must be provided by individual utilities seeking to implement Option I D. Specifically, (1) AdministrOtive procedures must be developed to establish power distribution controls that will guarantee that the reactor operating conditions are within the bases assumed for the exclusion region calculation.

(2) Calculations must be provided showing that the unfiltered flow-biased scram provides .

protection for the core-wide instability mode inside the administratively-enforced exclusion region. These calculations are dependent on BWR Owners' Group analyses that are due the (purth quarter of 1994 and are aimed at defining a critical gwer ratio correlation for unstable power oscillation conditions. *

(3) Reload confirmation procedures to ensure the validity of the exclusion region for each reload core must be provided.

INTRODUCTION This review is based on data compiled from a number of sources. The principal source is the licensing topical report NEDO-31960' and its supplement 1,2 which describe the bases for Option I-D. Report NEDO-31708 documented3 a study of fuel thermal margin during power oscillations and concluded that large oscillvions may violate specified acceptable fuel design  ;

hmits without automatic scram protection. A main sourcc of information for this review has l been a number of meetings between the BWR Owners' Group and Nuclear Regulatory ,

Commission (NRC) staff; dates for Option I-D specific meetings are 8/10/94,12/16/93, and i 3/4/93. In addition, the BWR Owners' Group has submitted a proprietary licensing topical report GENE-637-018-0793 DRF-A00-04021, entitled Application of the " Regional Exclusion with Flow Biased APRM Neutron Flux Scram Stability Solution (Option I-D) to the Vermont Yankee Nuclear Power Plant", which describes the application of the Option I-D concept to the lead plant (Vermont Yankee). Vermont Yankee has also submitted for NRC review a letter report

  • that contains answers to a request for additional information and the proposed j modifications to the technical specifications.

NRC staff has reviewed Option I-D along with the other long term solution options and l issued an SER., This SER referenced an ORNL technical evaluation report that revie'ved the licensing bases for the long term solutions. The staff SER 3asked a number of specific i 2

%-- +- * -- _ __ --- - . - - - _ --.m_ __-_-___ __._______.__

questions that would need to be answered before Option I-D would become an acceptable long term solution. Most of those questions were answered in the letter report of ref 4.

KEY OPTION I-D FEATURES Compliance to General Design Criteria (GDC) 10 and 12 is accomplished within the Option I-D solution by demonstrating that instabilities are unlikely and if they occur, specified acceptable fuel design limits (SAFDL) are satisfied for the expected operating conditions.

The arguments for Option I-D compliance with GCD 10 and 12 are as follows:

(1) An exclusion region is enforced by administrative procedures. Instabilities are demonstrated by analyses to be very unlikely outside this region. Intentional entry into the exclusion region is not allowed. Upon unintentional entry, the operator is instructed to exit the region immediately.

(2) In case the reactor is operated inadvertently inside the exclusion region, the unfiltered flow-biased flux scram provides protection for the most likely mode of oscillation, which is demonstrated by analysis to be the core-wide oscillation mode.

(3) Automatic protection for the out-of-phase mode (which is unlikely to occur) is only provided if the average power and flow are close enough to the scram setpoint for the flow-biased flux scram. The likelihood of out-of-phase instabilities is demonstrated by analyses to be low.

(4) Administrative controls are provided inside a conservatively-defined restricted (or buffer) region to enforce power distribution controls that guarantee that the reactor operating conditions are within the bases used to calculate the exclusion region.

Intentional operation inside the restricted region requires power distribution controls.

Upon unintentional entry, the operator is instructed to establish power distribution controls or exit the region immediately.

There are two main requisites for applicability of Option I-D to a particular plant:

(1) The plant must have an unfiltered flow-biased scram that provides protection in case a core-wide oscillation is developed at any operating condition inside the exclusion region.

(2) Out-of-phase oscillations must be demonstrated to be highly unlikely by analysis. To satisfy this criterion, the plant must have a tight core inlet orifice to maximize the single-phase pressure drop, and it must have a small size core to maximize the eigenvalue separation between neutronic modes.

3

' mr ~t.3ng Q3 CONCERNS We have two main concerns with Solution I-D:

(1) Given enough operating time, instabilities will happen in Solution I-D plants because of unintentional entries into the exclusion region (e.g. a LaSalle type event). If they occur, it will be up to the operator to reccgnize them and to terminate the oscillations by inserting control rods (unless the oscillations grow large enough to trigger the flow-biased flux scram). The exclusion region in Solution I-D is only controlled administratively; therefore, unintended entries into tpe region (for example, by automatic recirculation pump trip such in the LaSalle event) cannot be avoided. i 1

(2) If an out-of-phase instability were to occur at operating conditions with significant l margin to the scram setpoint (an unlikely event), the local power oscillations can grow large enough to cause violation of specified fuel design limits (SAFDL) before l the operator can recognize and terminate the event, or the flow-biased flux scram is l triggered. l Concern number (1) above is not really a technical concern, but a regulatory one. If Option I-D solution is approved, we are recognizing that instabilitie: (though unlikely) may occur.

The regulatory position here is that if instabilities were to occur they can be easily detected and suppressed as long as they are not of the out-of-phase typs. Thus, there is a good technical argument to state that General Design Criteria are satisfied for in-phase oscillations.

Concern number (2) above is a technical concern, and the basis for the acceptability of Solution I-D. The only way for Solution I-D to satisfy the General Design Criteria is if out-of-phase instabilities are demonstrated by analyses to be extremely unlikely. Based on our review of data presented by the Boiling Water Reactor Owner's Group (BWROG), and our own calculations using the LAPUR code, we conclude that small-core plants with tight inlet orifices are more likely to exhibit in-phase instabilities thn out-of-phase instabilities as long as " reasonable" axial and radial power shapes are maintained.

Our own analyses indicate that out-of-phase instabilities are possible in small-core, tight-inlet-orifice plants, but this requires highly peaked axial and radial distributions that can be precluded by administrative procedures during startup and low power maneuvers (see appendix A). Thus, the acceptability of Solution I-D from a technical point of view is dependent on these administrative procedures for power distribution control inside the restricted region.

Operation at full power reduces the available degrees of freedom to select highly peaked power shapes because the reactor is constrained by critical power ratio limits. Operation at low power, however, allows the operator the freedom to select a number of highly peaked power distributions that are detrimental to the system stability. Within the Solution I-D 4

I framework, unintended entries into the exclusion region are only likely to occur from high j power and be caused by loss of recirculation flow. Thus, unintended exclusion region entries

{

are likely to have " reasonable" power shapes and not result in out-of-phase oscillations. An l

unintended entry with the highly peaked power shapes typical of startup conditions would '

require the uncontrolled withdrawal of control rods (a highly unlikely event) or a severe feedwater temperature transient.

]

l REVIEW CONCLUSIONS

= l From a purely technical point of view, the arguments presented by Solution I-D plants have value, and we agree that in-phase instabilities are significantly more likely than out-of-phase instabilities in this type of plants. *Ihus, if instabilities occur, they are likely to be detected and suppressed by the unfiltered flow-biased scram system.

The proposals presented so far, however, do not provide for any documented controls on:

(1) reload confirmation analyses, or (2) power distribution controls during startup and low power maneuvering. We recommend that power distribution control requirements and reload confirmation analyses similar to those required in Solution I-A plants be required in Solution I-D plants. These include specifically:

(1) Reload confirmation analyses to confirm the validity of the exclusion region for the i new core loading.

(2) Administrative procedures to maintain power distribution controls in a " restricted" l region significantly larger than the exclusion region. These procedures must I guarantee that the reactor operating conditions are within the bases assumed for the exclusion region analyses, i (3) Stability analyses showing significant margin must be required to load Lead Use Assemblies (LUAs), which could lead ta local thermohydraulic instabilities for which Solution I-D does not provide any protection. I Power distribution controls that are technically acceptable include:

i (1) Maintaining a core-average saturated boiling boundary greater than 1.2 m (4 ft). This

, power distribution control has been reviewed for Solutivu i-A plants and found acceptable.'

(2) The use of a stability predictor. A predictor is essentially a qualified stability code that is cotpied to the plant computer. There are two types of predictors:

(a) On-line predictor. In this case, the time response should be adequate to 5

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provide timely information to the operator of the stability condition of the plant during startup and low flow operation maneuvers inside the restricted region. The predictor information should be available to the operator beforc major rod withdrawals and other transient operations such as recirculation pump upshift.

(b) Off-line predictor. Tnis is the case of precalculated startup sequences, where the power distributions and reactor stability are calculated off-line prior to  ;

startup or low-flow maneuvering. In the case of an off-line predictor, administrative procedures must be providui to ensure that the power distributions achieved are similar to those assumed in the off-line analyses.

1 l

(3) The use of an on-line stability monitor that measures the reactor stability. The l stability monitor must be qualified for both, the core-wide and out-of-phase stability modes. As with the on-line predictor, the stability monitor must have an adequate  ;

time response to provide timely information to the operator of the stability condition ,

of the plant before major control rod withdrawals or transients such as pump upshift. l Extremely fastjime response (of the order of seconds) is not required for this l

.gjdcation because power distributions controls are intended for startup and low-flow

  • maneuvers, which do not have a fast time constant.

i Long term solution I-D relies more heavily than other options on computer calculations to define the exclusion region and to insure that the expected oscillation mode is core wide. In stability calculations, input preparation is the major source of error; therefore, to maintain the t0.2 accuracy assumed in the core-channel decay ratio criterion map, any new calculations must use procedures similar to those used in the qualification bases. To insure tha: input errors do not compromise the accuracy of the calculations, we recommend that exclusion-region and region-confirmation calculations follow the input-generating procedures described in NEDO-31960. The input must then be reviewed to guarantee that the following minimum 2equirements are satisfied:

(1) The core model must be divided in a minimum of 24 axial nodes (2) The core model must la k ided into a series of radial nodes (i.e., thermal-hydraulic regions or channels) in un a manner that (a) No single region can be associated with more than 20% of the total core power generation. This requirement guarantees a good description of the radial power shape, especially for the high power channels.

(b) The core model must include a minimum of three regions for every bundle type that accounts for significant power generation.

6

(c) The model must include a hot-channel for each significant bundle type with the actual conditions of the hot channel.

(3) Each of the thermal-hydraulic regions must have its own axial power shape to account for 3-D power distributions. For example, high power channels are likely to have bottom peaked shapes.

(4) The collapsed 1 D cross sections or point kinetics parameters must represent the actual conditions being analyzed as close as possible, including control rod positions.

I 4

1 7

4

l REFERENCES

1. General Electric Company, BWR Owners' Group Long-Tenn Stability Solutions Licensing Methodology, NEDO-31960, May 1991,
2. General Electric Company, BWR Owners' Group Long-Tenn Stability Solutions

, Licensing Methodology, NEDO-31960 Supplement 1, March 1992.

. 3. General Ele'ctric Company, Fuel knnal Margin During Core hrmal Hydraulic Oscillations in a Boiling Water Reactor, NEDO-31708, June 1989

4. Letter, Vermont Yankee' Nuclear Power Corporation to USNRC, " Proposed Change .

No.173, BWR Thermal Hydraulic Stability and Plant-Information Requirements for BWROG Option I-D Long Term Stability Solution", BVY'94-36, March 31,~ 1994

5. Letter, USNRC to L.A. England (BWROG), Acceptance for Referencing of Topical Reports NEDO-31960 and NEDO-31960 Supplement 1. "BWR Owners' Group Long Term Stability Solutions Licensing Methodology" (TAC No, M75928), July 12,1993.
6. . ORNLiNRCILTR-92115, Licensing Basisfor Long-Tenn Solutions to BWR Stability Proposed by the BWR Owners' Group, Jose March-Ixuba, ORNL letter report.

August 1992 e

8

APPENDIX A LAPUR STUDY OF POSSIBILITY OF OUT-OF-PHASE INSTABILITIES IN SOLUTION I-D PLANTS '

To evaluate the possibility of out-of-phase instabilities in Solution ID plants, we have performed a number of LAPUR calculations for a representative Solution I-D plant (Ver.nont Yankee) using axial and radial power shapes from actual instability events. -In particular, we have used the power shapes of the WNP2 instability event of August 1992, and the Ringhals event of 1989. -

~

Ihe results indicate dat out-of-phase instabilities .cannot be precluded by analyses unless significant restrictions in power shapes are imposed. ' Our LAPUR calculations indicate that .

if Vermont Yankee were operated with the power distribution of WNP2, the plant would be.-

unstable and the oscillations mode.would be undetermined (i.e., it could be either in-phase or out-of-phase). -If Vermont Yankee were operated with the power distribution of Ringhals, the plant would be unstable and the oscillation mode would be clearly out-of-phase.

Figures 1 and 2 show the axial power shapes used for the above two cases. The radial power distribution is shown in Tables I and 2. The main results of the LAPUR analyses are summarized in Tables 3 and 4 and Figure 3. As it can be observed, using these power distributions, we cannot preclude out-of-phase instabilities in _ Vermont Yankee either using -

the LAPUR out-of-phase stability methodology or the BWROG core versus channel decay ratio methodology (see Figure 3).

I 9

Table 1. Radial Power Distnbution for WNP2 case Region # Number of bundles Relative Power (%) Relative Flow (%)

1 8 192 84 2 33 163 92 3 100 136 100 4 . 60 101 109 5 56 80 113 6 56 60 115 7 55 40 68 Table 2. Radial Power Distnbution for Ringhals case Region # Number of bundles Relative Power (%) Relative Flow (%)

1 4 157 92 2 24 143 96 3 930 123 102 4 102 119 104 5 59 99 109 6 42 41 112 7 41 31 61 10

Table 3. Summary of LAPUR-calculated decay ratios for WNP2 power shape Power (MW) Flow (Mlb/h) Decay Ratio Core Wide Out-of-phase Hot channel p = -$1.00 700 15.4 (32 %) 0.55 0.71 0.65 860 15.4 (32 %) 0.85 0.99- 0.95 860 19.2 (40 %) 0.38 0.61 0.61 1000 19.2 (40 %) 0.70 0.% 0.87 Table 4. Summary of LAPUR-calculated decay ratiet for Ringhals power shape Power (MW) Flow (MlblS) Decay Ratio Core Wide Out-of-phase Hot channel p = -$1.00 700 15.4 (32 %) 0.74 0.62 0.57 860 15.4 (32 %) 1.08 1.14 0.89 860 19.2 (40 %) 0.68 0.55 0.54 1000 19.2 (40 %) 0.90 0.91 0.76 1100 19.2 (40 %) 0.98 0.97 0.95 1200 19.2 (40 %) 1.04 1.07 1.13 l

11

Table A,1 LAPURX Input Detk for %M2 Case 7, l. I, l, l. 1, 1. I W , Tess 2 $se set Es . WNP2 Sepus 17 I I all 29 10m., M0., ese., t5 alin 0.ca, 0 0,0 63, 8 A i0 2 i DI.m 7, 4, 0, I, 0, 0,0, I,0 19 5 1 802.00

& 35, 26 30, 24 38 M 3 e i 102 00 15 m,13 SB. IS.4L 13.38,15 88, ISE IS 5 21 ISE 13.5, ISA 155,15 m,15 80, IS 5 8 l.M ISJa, IS.M. IS.m, ISE LSE 13.38, 15 5 22 134 ISA B5.5, t5.8, 843 1 0.1 ISE ISA ISAR,134 13AB,ISA ISAB D (SAI,135,13.5,13JE, IS.at,13.5, ism I 0.1 15.88, 43Js,154134 IS.at, IS AR,15.38 34 ISJB, ISAB, IS.at, IS.as,143 3 tJ 85 08, 15.88, 13 4 ISA ISA ISAR, ISJB D ISA 434 ISS. ISA ISA IS.as, ISAS I etl25 IS at,18J0, tS EB, ISE ISA R$ se, ISJs 3s 95 SB,13 3. ISA 134 tem 7 I, I, I, I, 5, I, i la as, 85 m, ISE ISA ISS,15 m, IS aB 27 IS 5,15 5,154 ISE L3.5, ISE 13 m i 10.42 IS 5. 83 05,15.a8, IS es, t$ at, ISJa,15 at 3 ISM,83as,ISA 1580,642 e i cent ,

IS E 15 m,il 5,152,ISJB,la88,13al 29 15 m,155 le a, ISA 13 38. ISAR. IS.m 8 0.SSee 15 m, ISJa, aSE IS St. IS at,13.m, l$10 30 15.80,15 m, ISE IS m, 543 1 0.0373 ISEISAISA 15.5 , 13 4 IS E ISJe 31 15415 m,15 5,15 IB, IS.M.15 m, lim 1 0ABIS IS m,15 ER,15 m, 65 ER, Ism, ISJE, ISJB 32 ISE 13.s8, IS.as,13 Es, lem 1 0.1336 5 33 0.344 IJ18, lJ23, l.M3,1.0t3. I.7% 1.827 l 0 0tle 1.4% i J15, l.275, 8.188, I Ask I A28,0.950 34 0 m3, 0.E34, 0.706,OJBee, O GN,0.3dL 6.49 7, I, 1 I, l. I, I, 1 0.45,0.330,0.83A 024, GA 33 0348, 8.3e1, IJER, 0.985,1.81% 1 Jed, IJN I I l.413, IJ25,1.2SA l.190,1.14 l AB0, I A3B 36 0.tEI,0.ml,0.ast 0.1e8,0. set 0. AIL 4.343 eli2 0 45% 0.344 0.133,GADI, to 37 0.31% IJ34, l.103, l.818, l.dm. IJ33, l.at$ t .e I.ms, l.341.2141.3% l.tSt 1.44, i ADt 53 i A27,0.841,0 892, SJ13. 0.7% 0.a13,0.3s7 t .E.2 1.E.2 1 E.2 2 E.S l .E-3 i E.9 l.E.2 S.E4 0.410, SJ77,0.140,0.0e% GA $4 0 415,1.3m, IJa$. I.ms, I es1, l. Set, l. des t 25 1 #7, l.334, l.253,1.36,1.las t 010, t 413 36 0 953, SJee 0.817, 0.am, 6,.. w.de1, 0.30s il 52 13 0 0.388, 4 ele. 0.312. 0.6 te, 04 0 0 413, l.335, 8.714,1,7% l.13. I.coe, 8.41 1.3E3,1.293, l.229,1.192, l.140, imi, l Alb 0.964, 0 89L 4.833, 0.7en, 0.488, 0.527, 0.533 0 478,0.3?a,0714,0.1% 04 0.ms,1327, l.se, 3.135, i.ee, IJlf, l.as IJ:L 3.363, l.229, IJuk 8.173, 3.133, I A77 i At3, e te, SJae,0.883, 0.737, 0.ast, GLSes e soi, e anB, eso, 0.8 64, GA 7

7, I, L 3. A S, A 6 0

7, 13.1 33.3, 135., MA, as a, 13 4, 22.0 to 1, GA GO S, e,A, 40, SA 4A 190 4 Il

7. O GIS, 0 800, O GIL 0 duk 0 000, 0.858, e allB IS 7 S., G., 0., 0., G., G., 8.

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^ Table A.2 LAPURW Input Deck for WNP2 Case L

' W . Tem 3 fm Ase ID k

I k

' 7. l. I 2

s, 3A - see, es, mg . ss 3  !

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4 e.x .. i s

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- 41.1054, 0.188 3. Issa,1.835 3, 6.2884,2.2154 e

i 4 sale 0Alad, 0.llit, eIslew 8.13st 3 Ales '

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  • to I e.0 11 1 5 12 0 . e.es.3 17 3.M Em te l 1, t le 1.1.1. 4. 8.1. I N

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$JA SJo,11.el. 87.le, le $2. 3.E 214 J2 at GA s.30, e.38, e4 e.as, e g e.se e 33, e4 04 048, s.4 e4 Im 23 ei I 8 I I eeeeeeee eeeeeeee 34 1.1.1.1. l. f.1, l. 3.1, 8 3

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Table A.3 LAPURX Input Deck for Ringhals Case 7, t. . 4 I, 1 f. 4 YY. Tem ) for Sal D . Itsalmis P,etasse . t7

  • I I 418.29 199 Seo 940.. l$ ded. 0.85,0.0,0 43,1 A 18 2 l 234.96
1. 48, 0,1. 8. O, 0, t, e t9 1 5 102 00 4 28 28 23 23 28 28 2 4 l 102.03 is.36 85D 15. 2 IS 34 is 24 15.34 15.34 21 f f.34 IS.38 liN 13.34 15 34 IS 24 19 34 4 1.M 15.34 15.34 13.34 13.M 13 M 15.34 IS M 22 l$.34 15.M 15.34 IS *.4 35.24 45 2 8 0.1 IS M t$.34 ISD *1'5 34 65.24 13.34 15.24 23 ISD 15.34 13.34 ISD 15.34 t$ 34 13.34 1 0.8 I S.M IS M 13 38 13.38 13.34 15.34 .5 34 M 83.2 IS 3s $3 34 ISD (SD 45.33 1 1.3 13.34 85.24 13.34 1134 15.24 ISD 15.34 25 1$Je LS M 15D 15 34 l3.34 15 34 15.34 1 0.125 t$.M 4$ 34 15 34 15 34 l$.34 15.34 ISD 28 15 34 ISD 45.24 ISD 13.24 49.33 7 1 l. 1. l. l. l. I IS.M is.M 15 34 15.24 15.34 IS M 13.24 27 15.34 15.24 la.34 IS 24 15 34 4134 1$ 24 I 10.42 35.34 ISD 15 34 45 34 19 24 113e 83.24 3 13 34 tim 19 34 13.24 t$ 34 43.33 I 1.040s 15 W 1134 11 34 la M i3 34 IS 34 13.34 29 l 13.34 13D 15.N :3 34 , 15.24 15.34 IS.24 4 0.3106 l 83J4 IS 34 13.34 ISD ' If Je IS 34 11 24 N g 15.34 63.34 15.34 11.34 15.34 45.53 t OA373 113e IS.M 15 3 15 34 13.34 IS 24 15.24 31 11J4 13.34 15 34 15.34 15 34 tim 1134 1 0.5 13 15.34 11 2 13 24 15 34 15.34 15 34 15.34 32 11.34 15 34 13.34 13.34 ISJe 43.53 1 0.1336 5 33 el 1.19 SAF 3.3 2.10 2D 2.25 1.06 1 0.0114 las 1,74 8.43 IJ2 f .42 ID ID M 1.22 8.10 B.12 LAB t es ON 0 95 7 1 t. 1 l. 1 8. l SD 0.3 00 0 35 0.as 13 62 1.t2 2J2 2.04 2.35 2.12 t .92 1.16 I I tm IJD t .44 1.32 1.24 8.19 1.13 M tm 1A3 0 99 0 96 0.99 05 0.0. 4t tD 0.10 0 et 0.M 0.35 em 31 63 O ss 20s 2.M 2.12 t 99 1.03 1.s i.e 1.54 B .43 1.33 1.27 1.19 1.44 ist 33 1A4 0 99 0 es 0 95 0.M 0 $$ 0 si 1.02 1.E 2 l .E.2 2.E.$ t .E.) I .E.9 t .E.1 SE4 0.18 0.m 0.33 0.M 0 00 M 64 0.10 1 83 2.00 2.01 1 87 8.71 1M i 25 1.43 1.M l.38 1.19 8.83 1.12 1.10 M 1A8 t .02 0 99 0.9s 0 95 ON 16 12 13 0 O SS 0.71 0 37 0.35 OAD 0 j abrS 0 00 2.30 2.32 1m 1.83 l ed 1.30

- 1.)? 1.25 8.E I.13 t ot 1 41 0 97 0 92 0N 0 $$ e 22 0.79 0.73 0.72 0 47 0 30 08 0 30 0.tJ etre 0.31 0 61 0m e e6 0 10 0.m 0 e6 0 43 0.e2 0# 0.3B 0.M 0.33 0.53 0.33 0.32 0 St OD 0.48 0 47 4 48 0 43 039 0.32 0.21 0 09 7

f, l. 2, 3. 4 S. 4, 6 9

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le I, 4, 27 93, 102, $9, 42, 41 IS 1, 42, 02, 42, 42, 62. 62, 42 le 14

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  • Table A.4 LAPURW Input Deck for Ringbals Case . [

VY . Tess 3 lar Sol ID % y g.

7. I. I

> 2 i 4, 27 fl. let. - - Se, 42. el 3- .

All A0  !

4 0.36, OR 3

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4 4A134, 8018% 0.181% ORML I.813, 3 815 .

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12 1 4.08 5-17 2.44843 it

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l. 8. l. I,1. B. I 3

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l 15

WNP2 POWER SHAPES A 2. 5 -

X -

cs- 1 I i . CH- 2 A 2

--V- CH- 3 L -.

O cn_4 P q.5 -.

/

'A\,, s, m cs- 3 O -y ^

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P E O

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0 5 10 15 20 25 30 NODE #

Figure 1. WNP2 axial power shapes 16

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AINGHALS POWER SHAPES A 25 X =

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I r . . ,

i CH- 2 2

A L g ,( cs-3 v CH-4 P q.5 -- -

' s' X cs-s O

W 4 x m

v CH- 6 gy .

E

+- cs-7 R :s l?

S --

g 0.5 A

P

~~

E O 0 5 10 15 20 25 30 NODE #

Figure 2. Ringhals axial power shapes 17

~

n.~. ,

I' Vermont Yankee. Using Instabiiity Event Power Distributions 1.2 C

O O

....-O.

R 1

___g..

E ,

,g .

9 0.B ,- ,

E o- '

C g_g - ,.-

~ '

A .. -

y Power Distrabution ,

,/

=

O.4 -

Ringhals / 33% Flow <

R ~~-*-~

Ringhals / 40% Flow A m 0.2 - v WNP2 / 33% Flow T

' - I+ - ' WNP2 / 40% Flow l

O g i i i i O O.2 0.4 0.6 0.8 1 1.2 HOT-CHANNEL DECAY. RAT 10 Figure 3. Core versus hot-channel decay ratio map for Vermont Yankee conditions 18 -

+

_ . . _ . - . . - _ . . - . . . . . ... .,.. - - - . . . , . . ,

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