ML20126D283
| ML20126D283 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 12/18/1992 |
| From: | GENERAL PUBLIC UTILITIES CORP. |
| To: | |
| Shared Package | |
| ML20126D280 | List: |
| References | |
| NUDOCS 9212240117 | |
| Download: ML20126D283 (20) | |
Text
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CRITICALITY SAFETY ANALYSIS REPORT EOLTHE THREE MILE ISLAND UNIT 2 REACTOR VESSEL 9212240117 921218 PDR P ADOCK 05000320 PDR .
_. ]
h..a _ e. , - . + . - 4,_ ,_ 4
- 4
- I TABLE OF CONTENTS ,
SECTION f%QE
1.0 INTRODUCTION
1 2.0 RESIDUAL FUEL CRITICALITY CHARACTERIZATION 1 2.1 STEADY STATE CRITICALITY CHARACTERIZATION 1 ;
2.2 ACCIDENT CRITICALITY CHARACTERIZATION 2
3.0 CRITICALITY EVALUATION
S 3 .
3.1 CRITICALITY METHODOLOGY 3 3.2 STEADY STATE CRITICALITY EVALUATIONS 5 3.3 ACCIDENT CRITICALITY EVALUATIONS 6 4.0
SUMMARY
OF RESULTS 7 4.1 STEADY STATE CRITICALITY EVALUATIONS 7 4.2 ACCIDENT CRITICALITY EVALUATIONS 8
5.0 CONCLUSION
S 9
6.0 REFERENCES
10 TABLES 11 FIGURES 15
CRITICALITY SAFETY ANA1.YSIS REPORT FOR THE TMI-2 REACTOR VESSEL
1.0 INTRODUCTION
The purpose of this report is to provide the results of the Three Mile Island Unit 2 (TMI-2) Reactor Vessel (RV) steady state and accident criticality safety reanalyses performed by the Nuclear Engineering Applications Department (NEAD) of the Oak Ridge National Laboratory (ORNL) (References 2 and 3).
The analyses were performed using conservative criticality models which were designed to bound the most credible fuel configuration. The upper bound of the mass of residual fuelin the TMI-2 RV has recently been quantified using a passive neutron measurement techn!que (Reference 1). The ORNL analyses demonstrated that the TMI-2 RV will remain subcritical by a substantial margin for both the steady state and accident configurations even with the conservative criticality models.
2.0 RESIDUAL FUEL CRITICALITY CHARACTERIZATION The previous " original" criticality safety analysis (References 4 and 5) was performed based on a visual estimate of the residual fuelin the TMI-2 RV. The upper bound fuel mass quantity for the TMi-2 RV, obtained from the passive neutron measurements program, will be documented in a forthcoming TMI-2 Post-Defueling Survey Report. For the passive neutron analysis, the TMI-2 RV was divided into nine horizontal zones as shown in Figure 1. Neutron measurernents were made as the RV water level was dropped from zone to zone. The resulting set of simultaneous equations was solved to determine the quantity of residual fuel (i.e., UO2) on a per zone basis. The criticality safety analysis presented here conservatively used those results which are viewed as the upper bound of the fuel remaining in the TMI-2 RV. Fuel that is enriched to less than 5 wt% Uranium-235 cannot be critical without an interspersed moderator (Reference 10). The originai TMi-2 core contained fuel enriched in 2.96 wt% U-235, i.e., less then the 5 wt% limit. Therefore, for the purposes of this analysis, it is conservatively assumed that the TMI-2 RV is completely filled with unborated water.
2.1 Steady State Criticality Characterization A comparison of the visual estimate and the upper bound fuel estimate from the passive neutron measurement is provided in Figure 2. The following discussion examines the upper bound residual fuel estimate by zone and characterizes the contribution of each zone to a potential steady state criticality in the TMI-2 RV.
The Zone 1 upper limit is approximately 10 kg of residual fuel. Ten kilograms of UO2 is much less than the Safe Fuel Mass Limit (SFML) of 1
140 kg (Reference 5). Furthermore, the zone is neutronically separated from the other zones (i.e., approximately 30 centimeters (12 inches) of water (Reference 10)). _ Lastly, the conservative criticality model developed by ORNL for Zones 2,3, and 4 as described below more than adequately accounts for this residual fuel. Therefore, this zone was not considered further in those analyses.
Zones 2 through 4 upper limits are 225 kg,150 kg, and 99 kg, respectively. Since two of these quantitles exceed the SFML and there is no directly applicable analysis, a new bounding steady state criticality analysis was performed by ORNL as described below.
Zones 5 and 6 represent the Upper Core Support Assembly (UCSA). The upper limits are 154 kg and 387 kg of residual fuel in Zones 5 and 6, respectively. Both Zone 5 and Zone 6 extend vertically for approximately 6.9 feet. The residual fuel in Zone 5 is primarily-comprised of extensive crusting (approximately 1 mm thick) on the outboard surfaces of the baffle plates. This crusting and the rest of the residual fuelis assumed to be aqually distributed at a radius of about 5.5 ft. (167 cm) from the RV conterline (i.e., at the radius of the baffle plates). The residual fuel in Zone 6 is primarily located adjacent to Zone
- 7. There is approximately 188 kg UO2 in the one inch annular gap between the core barrel and the thermal shield which extends from the bottom of Zone 6 vertically for less tnan six inches. An additional 67 kg is located in the orifice holes and on top of the lower grid rib assembly yielding a total of 255 kg for that part of Zone 6. The rest of the fuelin Zone 6 (i.e., approximately 132 kg)is assumed to be equally distributed at a radius of about 5.5 ft (167 cm) from the RV centerline. A negligible neutronic coupling over the nearly 14 vertical feet of Zones 5 and 6 is indicated from the original ORNL steady state analyses (Reference 2) which allows Zone 6 to be considered neutronically decoupled from Zones 7, 8, and 9.
Zones 7 and 8 represent the Lower Core Support Assembly (LCSA);
Zone 9 represents the Lower Head. The upper limits for the residual fuel in Zones 7, 8, and 9 are 113 kg, 89 kg, and 95 kg, respectively. As_
discussed below, the original criticality analysis remains valid for these zones.
2.2 Accident Criticality Characterization As stated above, the original criticality safety evaluation (References 4 and 5) for both the steady state and accident conditions was performed based on visual estimates and physical examinations of the residual fuel in the TMI-2 RV. As such, these evaluations not only identified the l location of residual fuel but also the fuel deposits' physical characteristics Using the data from these examinations and applying the 2
results of the passive neutron measurements, a conservative amount of loose fuel was estimated to relocate to the bottom head of the RV. This value bounds any credible reconfiguration of the remaining fuel deposits that exist in the TMI-2 RV (Reference 8). Table 3 reports these results by Zone and shows that a grand total of 620 kg of loose fuel is estimated to non-mechanistically relocate to the bottom of the RV.
3.0 CRITICALITY EVALUATION
S Two criticality evaluations were performed. The first evaluation used two different models to bound the RV fuel configuration for steady state conditions.
The second analysis evaluated the reconfiguration of the fuel following a non-mechanistic relocation of the loose residual fuel to the lower head of the RV. 1 The criticality methodology, including computer codes, cross sections, and pertinent modelling assumptions, are described for each of the evaluations J l
below. ]
3.1 Criticality Methodology i
l- 3.1.1 Computer Codes ;
1 '
3.1.1.1 XSDRN-PM i XSDRN PM is a computer code that was developed as part of the -
ORNL SCALE package (Reference 6) which, as a system of codes, performs criticality evaluations of complex critical systems.
XSDRN-PM is a one dimensional discrete ordinates neutron transport code that solves various eigenvalue problems ranging from determining the k-offective (k,,,) of a given system to i
performing a search for the critical dimension for a given k,,,. It is this latter mode that ORNL utilized for this study. An inherent foeture of the one dimensional analyses done with XSDRN-PM is-that all systems are also treated as infinite in height.
3.1.1.2 KENO V.a KENO V.a, another module of the ORNL SCALE system, was developed to analyze complex three dimensional geometries.
KENO V.a utilizes the Monte Carlo solution technique- for the neutron transport. This code was used in previousTMI-2 criticality evaluations, and most recently in the TMI-2 Defueling Ccmpletion Report (DCR) (Reference 5).
3.1.2 Cross Sections Cross section preparation was done with the same modules of the SCALE system as previously reported in Section 5.5.1.2 of 3-
Reference- 5. However, for _ this analysis it was decided to conservatively use the enrichment of 2.67 wt% U-235 associated '
with burned batch 3 fuel for all the modeled fuel. For the steady state _ case, the optimized ' unit cell' used to create the. cross sections was conservatively based on-the standard sized fuel pellet model with the dodecahedrallattice structure described in Reference 5 and an optimized fuel volume fraction of 0.28.
For the design basis accident case the optimized unit coll'used an optimized fuel fraction of 0.26 with 0.009 wt% boron in the unit-cell's fuel region. For all cases, steady state and accident,-
unborated water.was assumed to exist for the unit cell. For the ' q steady state case, no structural poisons (e.g., boron, zircaloy, or.- H stainless steel) were assumed. in the unit cell's fuel ' region. '
However, for the accident case a parametric evaluation 1was-performed in which the weight percent of boron and particle size were varied. See Table- 1 for a summary of the criticality methodology for the steady state case, i 3.1.3 Computer Code Benchmarking -
Section 5.5.1.3.4 of Reference 5 describes the basis for the analytical bias of 2.5% Ak, which includes the KENO V.a -
statistical uncertainty As noted the bias was used to establish a conservative margin for the highly borated water during .the defueling phase of TMI 2. However, for the present analysis, the water regions as noted in Section 3.1.2 containEno boron. t Therefore, the use of this benchmarking uncertainty is an additional conservatism for these analyses because the bias for !
unborated systems has been found to be considerably sma!!sr, i.e., on the order of one percent (Reference 7).
3.1.4 Summary of Conservatisms-As noted abovt, there were several significant conservatisms built i into the criticality evaluations. These are summarized below to',
emphasize the defense-in-depth concept inherent in these criticality evaluations: M
- The unit cells were constructed such that the fuel was in a 1 uniform geometric lattico composed of whole fuei pellets except for those accident analys cases where the fuel was considered-as infinitely dilute.
- No credit was taken for int'insic poisons, e.g., boron, stainte ;s steel, zircaloy, and control od debris except for the parametdc accident analysis cases. i i
s
- The residual fuel was assumed to be of the highest U- 135 enrichment, i.e., ba+ch 3 burned to 2.67 wt% U-235.
- For the XSDRN-PM analysis, the geometry was treated as if it were infinite in height.
- A calculational bias of 2.5% Ak was applied based on the highly borated defueling water even tnough pure unborated water was used for the moderator regicas in the analyses.
- The fuel region of the KENO V.a model was assumed to extend 360 around the periphery of the RV.
3.2 Steady State Criticality Evaluations 3.2.1 XSDRN-PM Steady State Evaluation An XSDRN-PM model was created by ORNL to determine the required thickness of an infinitely high annular shell of fuel to yield i a k,,, of 0.945 including the calculational uncertainties referred to above in Section 3.1.3. This k,,, value was chosen to be the same as the value that was determined in Reference 5 for the model of the fuel in the lower core support assembly. The outer radius of the shell was also constrained to 67.5 inches which was in agreement with the past ORNL analysis in Reference 5. This particular geometry for an annular shell was initially choser to depict the geometry of Zones 2 through 4. The thesis was. to show that the resultant thickness predicted by the XSDRN PM exceeded any known or postulated fuel deposits in those zones. _
Further, the results could be applied to other areas depending on the resultant thickness. For example, the thickest known fuel deposit outside of Zone 8 is the one inch gap between the thermal shield and the ; ore barrel. This gap also represents the largest -
physical annular region wherein residual fuel is known to exist.
As such, it would bound the maximum credible fuel deposit outside of Zone 8.
The XSDRN-PM analysis showed that the fuel thickness required to achieve a k,,, of 0.945 was 9.85 cm or 3.88 inches. This is equivalent to an axiallineal density of 29.7 kg/cm or 905 kg/ft of UO2.
3.2.2 KENO V.a Steady State Evaluation As stated previously, the original criticality safety evaluation (References 4 and 5) was performed based on a visual estimate of the residual fuel in the TMI-2 RV. The benefit of the video 5 !
evaluation was not only in' identifying where fuel deposits were .
located but also in identifying where no fuel deposits existed. -
Thorofore, a conservative criticality. model :was developed ~ that ~
bounded the observed conditions believed to be extant in theLTMI-2 RV. As discussed in Section _4.1.4, the computer:inodel and -
criticality evaluation which yielded the k ,, of 0.945 remains valid.
However, as an additional check for the steady state condition,-
ORNL reviewed the previous KENO V.a calculations (Reference 3),
i.e., the analyses that yielded the k,,, of 0.945 mentioned above.
The intent was to determine the amount of fuel that was modelled -
in the most reactive region of that KENO ;V.a model. In this instance, the controlling mass for criticality was the trapezoidal shaped region just under the lower grid forging (LGF) of the LCSA (See Figure 3). ORNL calculated (Reference 3) that this region would contain 986 kg of UO, assuming the entire trapezoidal region is filled uniformly throughout the entire 360 degree azimuth of the model. This amount exceeds the 838 kg of residual fuel estimated by the passive neutron measurement to ex1st in Zones 6 through 9.
3.3 Accident Criticality Evaluations 3.3.1 Criticality Criterion for Accidents -
A design basis value for k,,, of 0.99 was chosen for the present-accident analysis. This is consistent with the past TMI-2 licensing bases. For example Reference 5, Section 5.5.2.1.2, utilized th:::
criterion for the evaluation of accident conditions for the assumed-relocated fuel in the bottom RV head. Prior to that, Refere'nce 9-used the 0.99.value as the design basis k,,, to support recovery.
activities through RV- head removal for _ postulated accident conditions.
3.3.2 Criticality Model for Accident Conditions As discussed in Section 2.2, 620 kg of loose fuelis assumed _to non-mechanistically relocate to the bottom head of the RVa This -
value (i.e.,620 kg) was used for the actual KENO V.a computer analysis (Reference 3), in order to form the-final fuel / moderator matrix, pure water is assumed to be mixed with the . fuel in an optimized fashion. For the design basis accident unit cell, the wnole pellet (dodecahedron model) was assumed along with an intrinsic 0.009 wt% B in the fuelitself with an optimized volume fuel fraction of 0.26. The use of 0.009wt% boron is based on TMI-2 debris sample data (Reference-5). All samples collected contained impurities; the minimum quantity of boron found in any-sample was 0.01 wt% For additional conservative representation 6
and to account for moasurement uncertainty, this quantity was t reduced by 10% No other impurities were assumed to exist in the residual fuel.
3.3.3 KENO V.a' Accident Evaluations ;
in order to evaluate the suberiticality for the above accident model, several additional parametric sensitivity analyses were -
performed using KENO. V.a. The results of ti;ese analyses are summarized in Table 4 along with the design basis. case._The parameters varied were particle size and boron content. The effect '
of . size was studied by the use . of. whole pellets and' a -
homogeneous mixture of fuel and water. The intrinsic poison,
-(boron) concentration was varied over the following values: 'O 0 ~
wt%,0.009 wt%, and 0.072 wt% Figure 4 displays the actual-geometry modelled. This is the same basic model used previously -
in Section 5.5.2.1.2 of Reference 5 to conservatively account for relocation of fuel debris to the bottom of the RV head. Region 1,-
height L i , contains the optimized fuel /unborated water matrix containing the 620 kg of fuel. Region 2, height L ,2 contains about _
500 gallons of unbarated water which represents an essentially ,
infinite water reflector. '
4.0
SUMMARY
OF RESULTS 4.1 Steady State Criticality Evaluations Table 2 summarizes the results of the steady state criticality evaluations =
discussed'in Section 3.2. The following sections present additional rationale to justify the steady state subcriticality_in..the regicns of.the TMI-2 RV that contain more than the SFML of 140 kg. ,
4.1.1 Zones 2 through 4 The major quantities of residual fuel in Zones 2 through 4 are at or near the hot and cold leg nozzles-(Reference l8). The largest quantity exists as a " pile" of fuel in the "2A" cold leg nozzle that is less than three inches deep; however, its density and UO f-percentage have been determined to ba less than " normal" loose; fuel material. In terms of UO 2, a three inch depth of this~ material is equivalent to a J.4 inch depth of normal loose l material, i.e.,
less than the one inch thickness of loose fuel in the. annular gap between the core barrel and thermal shield (Zone 6). Therefore, the XSDRN-PM analysis resulting in a k,,, = 0.945. for al fuel thickness of 3.88 inches bounds the maimum - residual fuel quantities that exist in Zones 2 through 4.
7
'4 4.1.2 Zone 5 As discussed in Section _'2.0,- the residual fuel in Zone 5 is-primarily_ comprised of a 1 mm thick crust on the baffle plates.
Therefore,'.the- XSDRN-PM analysis also bounds the maximum -
residual fuel quantity that exists in Zone 5.
4.1.3 ' Zone 6 The one inch annular gap between the core barrel and the thermal shield in Zone 6 contains ' residual fuel that extends circumferentially for a height of about six inches. 'Except for a resolidified mass underneath the LGF, the annular gap represents the largest discrete volume of residual fuel in the RV..The visual-examinations of the TMI-2 RV verified that there are no other significant masses of residual fuel in Zone 6. Therefore the XSDRN-PM analysis bounds the maximum residual fuel quantities that exist in Zone 6.
4.1.4 Zones 6 through 9 The complex geometry of the LCSA dictated the usage of the KENO V.a ' computer code. Figure 3 (Figure 1 of_ Reference'4)-
depicts the computer model for the steady ' state case as presented in the original criticality analysis. Table 2 (Table 2 of Reference 4) compares that model to the estimated residual fuel-masses as' of April 1990. Asistated in Section. 3.2.2, the controlling mass for criticality in the original steady state criticality -
analysis was a trapezoidal region located under the' LGF. This mass equaled approximately 986 kg (Reference 3), in the passiv~e neutron measurements program, the demarcation line between Zones 7 and 8 was the top of the LGF. Th1 he steady state criticality controlling mass is in Zone 8.-The quantity of residual fuel in'the visual estimate for Zone 8 was 133 kg. The passive neutron measurement upper. bound estimate for that zone is 89 kg. Therefore, the original computer model used in ~the steady state criticality analysis conservatively bounds the maximum quantity of fuel estimated to' be located in Zone 8; thus, the -
original analysis remains valid for Zones 6 through 9.
4.1.5 Zones 1 through 9 The final steady state subcriticality argument involves the entire -
TMI-2 RV.- Except for the " lump" of residual fuel under the LGF, nowhere does there exist an annular ring of residual fuel approaching 3.88 inches thick. Thus, completion of the TMI-2 Defueling Program (i.e., excision of an eight-foot diameter cylinder 8
e a from the center of the RV) has precluded the possibility of the-existence of an annular ring of fuel 3.88" thick. - Therefore, the combination of the XSDRN-PM . annular ring of _ fuel analysis and -
the KENO V.a analysis (Section 4.1.4) bound the residual fuel quantities extant anywhere in the entire TMi-2 RV.
4.2 Accident Criticality Evaluations Table 4 reprises the results .of the parametric KENO V.a criticality.
evaluations. As shown, the design basis case meets the design k,,, limit-of 0.99. The trend of k,,, decreasing with particle size for optimized fuel volume fraction is the same as in Table 5-9 of Reference 5. -
5.0 CONCLUSION
S Based on the criticality evaluations and suberiticality arguments,it is concluded' that the core debris that remain, in the TMI-2 RV is subcritical both for steady state and accident conditions. Furthermore, because of the inherent '
conservatism in the analyses used in this evaluation, there is a.significant-defense-in-depth safety margin built into all of the evaluations in this report.
i l-9
6.0 REFERENCES
- 1. TMI-2 Reactor Vessel Fuel Assay, C. Distenfeld, M. Haghighi, and B. Brosey, dated September 18,-1992.
- 2. a. ORNL letter, C. V. Parks to R. E. Rogan, date'd July 14,1992.-
- b. ORNL letter, C.~-V. Parks to R. E. Rogan, dated July 24,1992.
- 3. a. ORNL letter, C. V. Parks to R. E. Rogan, dated September 8,1992.
- b. ORNL letter, C. V. Parks to R. E. Rogan, dated September 24,1992.
- 4. GPU Nuclear letter 4410-90-L-0026, "Results of Post-Lower Head Sampling Program Cleanup," dated April 12,1990.
- 5. TMI-2 Defueling Completion Report.
- 6. NUREG/CR-200, L. Petrie, et al., " SCALE: A Modular Code System'for Performing ' ;
Standardized Computer Analyses for Licensing Evaluations," USNRC, Revision 3,-
December 1984.
- 7. GEND/071, R. M. Westfall, et al.,"TMI Criticality Studies: Lower Vessel Rubble and Analytical Benchmarking," DOE, May 1986.
~
- 8. GPU Nuclear calculation C312-7370-92-008,"TMI 2 Criticality Safety Analysis : ;
Model," Revision 0, April 1992, 1
- 9. J._ R. Worsham lli, " Methods and Procedures of Analysis for TMl-2 Criticality- I Calculations to Support Recover y Activities Through Head Removal " BAW-1738, June 1982.
- 10. Nuclear Safety Guide, TID-7016, Revision 2, J. T. Thomas, Ed., June 1978.
1 10
,7 cj
-ThBLE 1.
SUMMARY
OF STEADY STATE CRITICALITY EVALUATION MODEL' j 1
4 4
STEADY STATE WT% U-235 2 '.- 6 7 PARTICLE SIZE STANDARD PELLET FUEL VOLUME FRACTION 0.28; COMPUTER CODES' XSDRN-PM & KENO V.a WTt BORON O-OTHER POISONS' -NONE-- 2 l MODERATOR PURE WATER' K-EFFECTIVE < 0.945 l- I 11 l
. . ~ . _ . , - . _ . . , . . . - _ . . . . . . --
m-Table 2. Summary of Results of Steady State Criticality Evaluations .
Fuel Ouantity (kc)
Covered Zones Criticality'Model PNM* Upper Bound Estimate Model Estimatt 2-4 XSDRN-PM 476 9413 5 XSDRN-PM 154 6245.
6 XSDRN-PM 387 6245' 6-9 KENO V.a 684 2910 1-9 XSDRN-PM 1322 36,655 t
PNM is Passive Neutron-Measurement-12-
._, , - - _ _ . _ . . - . . - . = - _ _- -a
t
- Table 3. Summary of' Loose Fuel Estimates for Accident Criticality Evaluation Zones Loose Fuel Estimate'(kct) 1 10 2 225 3 -' 150 4 99 5 45 6 29 7& 8 :3' 9 59 TOTAL '620 m
I -'
a l,
I.
l p 13
JAB _kE 4.
SUMMARY
OF TMI-2 ACCIDENT CRITICALITY EVALUATION TASK MODELS, ACCIDENT ACCIDENT ACCIDENT ACCIDENT ACCIDENT ACCIDENT I' II3 III IV' V! VI ,
WTt U-235 2.67 2.67 2.67 2.67- 2.67 2.67 PARTICLE SIZE STANDARD STANDARD STANDARD . INFINITELY INFINITELY INFINITELY PELLET PELLET PELLET DILUTE DILUTE DILUTE COMPUTER CODE KENO KENO KENO KENO KENO KENO-WT%' BORON 1 0.009 0.072 0 0.009 0.072 0 OTHER POISONS NONE NONE NONE NONE NONE NONE MODERATOR PURE PURE PURE PURE WATER PURE WATER PURE WATER WATER WATER WATER FUEL VOLUME 0.26 0.26 0.27 0.24 0.23 0.26 FRACTION L i (cm) 18.67 18.31 18.31 19.44 19.87 18.67 L, (cm) 37.22 37.58 37.58 36.45 36.02 37.22 K-EFFECTIVE 2 0.981 0.735 1.023 0.948 0.719 0.984
+
8 The boron is assumed to be integrally mixed in the fuel region of the cell model, not in the external water.
3 Values for K-effective include the 2.5%AK in benchmarking uncertainties.
l l
i.
l 14 e , - - . . . .- - ew m y a .
FIGURE 1.
a l Internals h E
! I
! Indexing Core Il Support. - -
~ J (Fixture llF)
Assemolylg hl (CSA)s
! b fW" f '-
1- 4 ] @
h <i i
1 Core A ! Support W,
Shield b
w ; c q
v N@ ?;R
- Q . t 1- j g Reactor Downcomer i =
i Vessel Region ,= .
J
.=
@ ! j 3 Upper
! Core s' _
3 Support
{
_ -~
l' Assembly
.) (UCSA)-
@ =
i!
L
- t Lower
.\ 1,1 t m ' n ' '$ , r @ ) Core
\ gl,1) !zg yy ; an'I[J#$/,_ /@ Support
,7 7=- , - '
]
Assembly Bottom g .) (LCSA)
{ '- .) '
eg on Reactor Vessel Cutaway View 15
Possive Vsual Neutron
- Estimate Estimate
] " # D (Kg) (Upper Bound) 0 N 10 10 Zone 1 RX1URE j
62 s.s Zone 2 g 225 ;
J N '
f- -
o --
150 Zone 3 J 46 3 y . . r g 1.9 Zone _
4 27 A _ 7 6.9 UPFER 8 154 Zone 5 3Ise$Iy y
6.9 Zone 6 244 387
~
93 113
[4 - Zone 7 CoYE SUPPORT 89 #8"8#
133 1.2 Zone
~
- 8) y 97 - Zone 9
/
29 95 LOVER g HEAD 652 kg 1322 kg Totals Figure 2. Comparison of RV Fuel Estimates 16
, , , , . - -. . . ~
as e 67.5 inches (171.5 om) -
- f. ,. .
i
'l VEsstL' CL '. ? IJreoroted Water - -0.10*--
(Infinite Thickness)
Debris l 10'*0" Detris 0 1"-' '
Grid Elb 501 Water los as 5.25" 5.0" -Infinite Thickness-Debris tJrtorated -
---0.1 = 5.0" Water Reflector 0.1* Eaternal
.To vesset ,,
Distributor Piete 1.0*
d = 5.0* 45% Water 551 as Debris k 5.0*
Note: Drawing is --0.1" j.
not to scale 0.1" Lower Grid Forging- -l 50% Debels 501 ss 6.0"!
4. 0"
/4M . S.
l ,.
Unborated Weter / Debris
- 7=-- a= -
- 2.0"-
SS 0.5==
ms TaapezoioAL REGmN coNTuns TH: see ma.
AA = 20" Incore Cufde Tthe -
J l
Sipport Plate 2.0*
Urborated Water 40% Water 60% $$
(Infinite thickness) ' l .'
de 2= Debris 1.5" D 8" Steet 3 0.15" thickness e Reactor venet Is Welt
~ l J
m #. ore l:
f l
VisstL CL
.i i i FIGURE 3. STEADY STATE i.
KENO V.a MODEL-
-* - 1 FIGURE'4. ACCIDENT RV BOTTOM: HEAD MODEL l
e -
/\
Void Above Water
/ \
) .
l
'L2 4L \
r1 r2 =a L1 -
v 8" of- steel s
.unborated water "
infinite thickness-t p
r1 - 217.678 cm r2 - 237.998 cm 11 - he'ight of fusi region (620 kg U0 )2mixed with unborated water -
L2- height of remaining quantities of unborated water (total of '500 gallons unborated water) .
See Table 4 for specific values of Lg and L2 ,
18
.