ML20065M475

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Forwards Summary of Crbr/Nrc Hypothetical Core Disruptive Accident Energetics 820921 Meeting Re Plenum Fission Gas Compaction,Role of Structures in Energetic Termination & Fuel Removal & Energetic Potential
ML20065M475
Person / Time
Site: Clinch River
Issue date: 10/15/1982
From: Longenecker J
ENERGY, DEPT. OF
To: Check P
Office of Nuclear Reactor Regulation
References
HQ:S:82:105, NUDOCS 8210210273
Download: ML20065M475 (51)
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Department of Energy 9 Washington, D.C. 20545 Docket No. 50-537

-(3 HQ:S:82:105 0CT 151982 r

Mr. Paul S. Check, Director CRBR Program Office , . ,,

Office of Nuclear Reactor Regulation -C U.S. Nuclear Regulatory Commission ,

Washington, D.C. 20555 -s

Dear Mr. Check:

v

SUMMARY

OF HCDA ENERGETICS MEETING HELD ON SEPTEMBER 21, 1982 The meeting agenda, attendance list, and viewgraphs distributed at the subject meeting are enclosed as Enclosures 1, 2, and 3, respectively. The formal presentations and general discussion focused on clarification of technical issues associated with the CRBRP/P0 response to formal NRC questions. Presentations were made by both the NRC and CRBRP consultants. As a result of the meeting, the Project will undertake the actions listed in Enclosure 4.

Sincerely.

J n R. Longe ker Acting Directo , Of fice of the Clinch River Breeder Reactor Plant Project Office of Nuclear Energy Enclosures cc: Service List Standard Distribution Licensing Distribution 8210210273 821015 pol PDR ADOCK 05000537 A PDR

LNLLUbOHL 1 Pogn 2 of 2 Ar.CHDA citBi1P/IIRC llCDA Energetics liceting .

Sr pte.niber 21, 1982 Argnnne. Ib tional I.cbora tory Building 207 Con ference Poom DA-126 1..

Introductory rcuarks, (unc/CRBRP, is mi.n). .

2. TO.P cncrgetics potential (pin internal fuel motion, sweapout, inccher-nn c e ) , (CRDEP, 15 min - NRC, 15 min).
3. 1.0F-d-TOP potential (sodima void worth and other uncertainties), (CRBRP, 30 min - Rnc, 30 min).
4. Plenum fi s: ion Das compact. ton (energetics potential, clad relocation,

. :4 initiating powcr phase histories), (CABRP, 30 min - /mC, 26 min). ~

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5. Fuel remuval and cuerget ler. rotont.f al in connect.lon wit.h mci tout /ai nular.

pool phctu s (CRDRY, GO v1f *! - UliCa GO mist). -

G. Pole of struct.ui-es in energetic teminction, (CN?iRP, 25 min - luiC, .10 r:d n) .

7. Conc 1uding rnnneht., (CRUn!', 30 miss - VRC, 30 min 1 I

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ENCLOSURE 2 Y

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EELOSURE 3 CEBRP HCDA EllERGETICS MEETillG INITI ATING PHASE ASSESSMENTS 1

PRESENTED BY DAVID P. WEBER SEPTEMBER 21, 1982 ARGONNE NATIONAL 1.ABORATORY ARG0llNE, ILLINDIS 60439' 4

e e 6

1 CRBRP HCDA ENERGETICS MEETIllG INITIATING PHASE ASSESSMENT

  • TOP ENERGETICS POTENTIAL

= LOF'n' TOP POTENTI AL a PLENUM FISSION GAS COMPACTION 6

e

ASSESSMENT OF WHOLE CORE IMPLICATIONS OF MIDPLANE PIN FAILURES IN SLOW RNiP TOP IN HETEROGENEOUS CORE CRBRP WITH SAS/PLUT02 o EOC-410&/SEC SCENARIO

  • FAILURE MELT FRACTION, CAVITY PRESSURE, AND PARTICLE i

SIZE CHOSEN TO SIMULATE W2 EXPERIMENT

  • ALL FUEL PINS ASSUMED TO Fall C0HERENTLY
  • LEAD CHAN!!EL FAILURE (6) LEADS TO LOW PEAK POWER (4 5 Po) AND LIMITED POSITIVE REACTIVITY (10&)
  • LIMITED PLUTO-2 PREDICTED SWEEPOUT LEADS TO MORE RAPID POWER REC 0VERY THAN E0C-4 TOP CASE 2 (GEFR 523)
  • SUBSEQUENT DRIVER ASSEMBLY FAILURES AT LOW REACTIVITY STATE IMPLY SUB-PROMPT CRITICAL EXCURSION AND SUBCRITICALITY (PEAK POWER = 5 7 Po )
  • EOC-310C/SEC SCENARIO a E0C-3 CHANNEL. POWER FACTORS USED WITH EXISTING E0C-4 DATA

? SEC0llDARY ASSEMBLY FAILURES (Cal 11 AND 7) DELAYED Ill TIME (66 AND 82 MSEC) PREVENT SUPERPOSITION OF POSITIVE FUEL FEEDBACKS

= SIGNIFICAllT NEGATIVE FUEL REACTIVITY FROM LEAD CHANNELS WITilIN 300 Msec (~ 45) .

.A t t PLUT02 APPLICATIONS TO IN-PILE TESTS e PRE-TEST AND POST-TEST ANALYSES OF TREAT TESTS E8, H6, AllD L8 WITH PLUTO AllD PLUT02 o TREAT TEST E8

  • $3/SEc TOP FFTF SIMULATION
  • LOW PUMP PRESSURE AND INITIAL SODIUM VELOCITY

= FAILURE LOCATION ABOVE MID-PLAllE

= CONSIDERABLE EARLY SWEEP 00T WITH EXPERIMENTAL RESULTS FASTER AND LARGER THAN PLUTO CALCULATIONS o TREAT TEST H6

  • 50&/SEc TOP FFTF SIMULATION i a PROTOTYPIC PRESSURE DROP AND IlllTIAL S0DIUM VELOCITY a SEVERAL EVENTS SEPARATED BY MORE THAN 100 MSEC

\

o CALCULAT10ll AllD H0DOSCOPE SHOW SIGNIFICANT EARLY SWEEP 00T (10s WITHIN 30 MSEC AllD 28s WITH 90 MSEC) e TREAT TEST L8

= LOF'n' TOP SIMULATION FOR CRBRP A0M0GEllE00S CORE o DEGRADED POTEllTI AL FOR FUEL SWEEP 00T t

a FUEL MOT 10tl REACTIVITY NEGATIVE 20 MSEC AFTER R0D l

FAILURE.

a CALCULATED SWEEP 00T LAGGED MEASUREMEllTS l

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e CRBRP HCDA ENERGETICS MEETING INITIATING PHASE ASSESSMENT

= TOP ENERGETICS POTENTIAL

o PLENUM FISS10!! GAS C0KPACTION 4

e 9

VOID WORTH Ul1 CERTAINTY IMPLICATI0!ls ON LOF'o' TOP POTENTI AL o SAS3D MODELING ASSUMPTIONS BEST ESTIMATE SODIUM VOID REACTIVITY WORTHS PROVIDED BY AHL/AP SODIUM VOID "0RTH UNCERTAlllTIES BASED 011 AllL/AP ZPPR EXPERIMEllTAL RESULTS AND ANALYTICAL METHODS AllD DATA BASE USED Ill CRITICAL EXPERIMEllTS FUEL MOTION ASSUMPTI0llS IN SLUMPY BASED 011 RECENT AllL/ RAS L6/L7 AllALYSIS e KEY MODELillG P0iHTS i

i =

MAXIMUM POSITIVE COOLANT VOIDillG REACTIVITY PLUS TWICE UllCERTAlllTY RESULTS IN $219 VOIDING REACTIVITY l

=

EXPERil1ENTALLY C0llSISTENT FUEL NOTION MODELING PLAYS l ,

IMPORTANT ROLE IN ANY LOF'n' TOP ' ASSESSMENT l

l l.

l _ _ _ - - - _ _ _

V0ID WORTH UNCERTAlllTY IMPLICAT1011S ON LOF'n' TOP POTENTI AL o SAS3D WHOLE CORE RESULTS COOLANT BOILING IN ALL DRIVER ASSEMBLIES BEFORE LEAD CHANilEL (CH. 6) FUEL MOTION COMPLETE CORE VOIDING IN DRIVER ASSEMBLY CHANilELS 2,4,6,7,9,10 AllD 11 AT TIME OF CHAllllEL 6 FUEL MOT 10ll a PARTIAL VOIDING IN CHAllllELS 12, 13, 14 AND 15

  • POWER LEVEL IS LOW (~ 10 P o ) A!!D FAILURE C0!!DITI0lls ARE FAR FROM BEING MET IN LOW POWER CHAllllELS.

C00LAllT BOILING IN INTERilAL BLANKETS TAKES PLACE AFTER FUEL DISRUPTION AND GROSS DISPERSAL IN CHAllllELS 6, 2, 4 AND 7 o C0llCLUS10N l EVEN USING C0!1SERVATIVE ESTIMATE'S OF THE UllCERTAINTIES 111 C00LAllT V01DillG REACTIVITY,110 THRESHOLD FOR LOF'n' TOP EVEllTS WAS FOUllD WHEll EXPERIMEllTALLY VERIFIED FUEL MOT 10ll BEHAVIOUR WAS BKPLOYED i

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~~

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CRBRP HCDA EllERGETICS MEETIllG INITIATil1G PHASE ASSESSMENT o TOP ENERGETICS POTENTIAL

  • LOF'o' TOP POTENTI AL o PLE110M FISSION GAS COMPACTION 6

e O

POTEllTIAL FOR AUT0 CATALYSIS DUE TO PLEl10M FISS1011 GAS INDUCED FUEL COMPACTION

=

INITIAL ASSESSMENT (BASED ON GEFR-523 EOC-4 LOF BASE CASE 1A) SHOWED COMPLETE BLOWDOWil IN EARLY ASSEMBLIES BUT POTEllTIAL FOR CGiPACTION IN LATER ASSEMBLIES a

AUTOCATALYTit BEHAVIOR WAS AFFECTED BY C0llSERVATIVE MODELING OF EARLY FUEL MOT 10H e

TREAT LOF TESTS, ESPECIALLY L6 AND L7, WERE IDENTIFIED AS THE MOST RELEVAllT DATABASE AllD EXTENSIVE SAS3D/SLUMPY ANALYSES WERE PERF0miED o

FISSION GAS AVAILABILITY AND DISTRIBUT10ll WERE DETERMl!JED WITH FRAS3 CODE e

WHOLE CORE AllALYSES WERE PERFORMED WITH EXPERIMENTALLY CONSISTEllT FUEL DISPERSAL MODELING, LEADING TO ELIMINATI0ll 0F CollCERll FOR PLElluM GAS COMPACT 10!l e

FISS10!! GAS MODEllilG WITH FRAS3

  • TECHillCAL APPROACH VAllDATION OF FRAS3..MODELING BY COMPARISON OF PREDICTED AllD MEASURED GAS RELEASES Ill FGR TESTS WHICH MOST CLOSELY REPRESEllT CRBR C0!!DIT10lls PREDICT 10lls 0F THE FRACT10110F THE INITIAL FISSION GAS COUCEllTRATIONS RETAlllED AT TIME OF FUEL MOT 10!l IN L6 AllD L7 TESTS FOR USE IN SAS3D/SLUMPY PREDICT 10lls 0F GAS C0llCEllTRAT10llS FOR EOC-4 LEAD

' CHAllllEL 6 WITH LOF GEFR-523 BEST ESTIMATE THERMAL HISTORY a C0llCLUS10llS 011 GAS RETEllTION t

PERCEllT RETAltlED PERCEllT RETAlHED IN GRAlllS ON GRAIN BOUNDARIES L6 24 -

95

. L7 64 47 CH 6 54 47 l

SAS3D/SLUMPY ANALYSIS OF L6 AND L7 TREAT TESTS e TECHNICAL APPROACH PROCEDURE FOLLOWED FOR HEAT BALANCE AND TEST SIMULATIONS

=

STEADY-STATE SIMULATION OF 1RRADIAT10N HISTORY a

20-SECOND TRANSIENT TO SET INITIAL THEmiAL-HYDRAULIC CONDITION

FISSION GAS PARAMETERS BASED ON FRAS3 ANALYSIS FRACTION OF GRAVITY SET TO 0 2 o VERY LITTLE COUPLING BETWEEN COOLANT VAPOR STREN4, AND FUEL MOTION (0 SODOM = 0 02)

! o EFFECTIVE FUEL VISCOSITY ENHANCED TO ACC0llNT FOR PRESENCE OF PARTIALLY SOLID FUEL (VISFU = 10000)

I o FUEL MOTION INITIATED ON 50% FUEL MELT FRACTION i

i o TEST RESULTS a

SATISFACTORY SIMULATION OF BOTH L6 AND L7 TESTS l

WHOLE CORE AllALYSIS AllD PLEllUM GAS COMPACT 10!! ASSESSMENT WHOLE CORE POWER AND REACTIVITY RESULTS LEAD CHAullEL REACTIVITY STAYS POSITIVE FOR 146 MSEC, WITH PEAK POWER OF 4 7 Po a

REACTOR DRIVEN SUBCRITICAL ON LEAD CHANilEL FUEL MOTIO BY 406 MSEC a

ASSESSMENTS PERFORMED ON SUBSEQUEllT FAILURES AND TIM

=

POTEllTI AL FOR COMPACTION OF FUEL o

PIPFLO MODEllllG IN SAS3D AND 1400 C CLADDING TEMPERATURE FAILURE CONDITION USED l

o TIME C0llSTANT FOR BLOWDOWil CALCULA ED TO BE LESS THAN 250 MSEC a

ALL DRIVER CHANilELS HAVE SEVERAL TIME C0llSTAllTS TO BLOWD0l!!1 PRIOR TO FUEL MOTION INITIATION

  • C0!!CLUS10ll .

4 AUTOCATALYSI,S BY PLElluM GAS COMPACTI0ll 0F pills IS HIGilLY UllLIKELY i

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S0DIUM VOID WORTH ALTERNATIVE METHODOLOGIES 0 USE STATE-OF-THE-ART METHODS AND. CROSS SECTION DATA FOR CALCULA-TIONS. DETERMINE UNCERTAINTIES FROM " KNOWLEDGE" 0F UNCERTAINTIES IN METHODS / DATA.

0 USE INTEGRAL DATA BASE TO DERIVE AN " EXPERIMENTAL"'VALUE. UNCER-TAINTIES FALL OUT OF ANALYSIS O

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I BIAS FACTOR METHOD e SINGLE BIAS FACTOR P=aC e Two FACTORS (LEAKAGE AND NON-LEAKAGE) .

9 P = $N + il I

-E MIN [ (P 'I I)2 '

I 4

COMPUTATIONAL MODEL o ENDF/B-IV DATA 2

o MC -2/SDX PROCESSING TO 20 ENERGY GROUPS

~~

e THREE-DIf4ENSIONAL DIFFUSION THEORY 5 : ,.

1 e CORRECT FOR STREAlilNG USING BENOIST DIRECTIONAL DIFFUSION i$

COEFFICIENTS ,

, o EXACT PERTURBATION THEORY e

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9W Ratios of Calculated to tieasured Reactivities for Sodium Voiding C/E Before . Standard Devia-

., Cases Biasing tion After Biasinga CRBR-EMCb BOC-1, positive part of core 0.98 10

. 'CRBR-EMC EOC-4, positive part of core 1.23 6 101 mixed zones -

1.08 12 Axial blankets without control rods 0.91 1 Axial blankets with control rods 1.23 2 Core zones with negative reactivity signals- 1.02 9 a

Separate' bias factors applied to positive and negative components of reactivity. For any subset, the average C/E is 1.0 after biasing.

b Engineering mockup critical experiments foc sodium-void reactivity in CRBR; reactor geometry and composition closely matched.

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Ratios of talculated to Nessured Reactivities for Sodium Voiding C/E Before  % Standard Devia-Cases Biasing tion After Biasinga CRBR-EMCb BOC-1, positive part of core 0.98 10 CRBR-EMC EOC-4, positive part of core 1.23 6

, 101 mixed Jones -

1.08 12 Axial blankets without control rods 0.91 1

Axial blankets with control rods 1.23 2 Core zones with negative reactivity signals 1.02 9 aSeparate bias factors applied to positive and negative components of reactivity. For any subset, the average C/E is 1.0 after biasing.

b Engineering mockt? critical experiments foc sodium-void reactivity.in CRDR; reactor gc00 try and composition closely matched.

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Bias Factors and Uncertainties for Sodium-void Reactivity in CRBR Calculational Bias Factora Uncertainty,b%

Zone BOC-1 EOC-4 BOC-1 EOC-4 Central core 1.0 0.82 10 6 /

External core 1.0 1.0 10 10 Axial blankets 1.0 1.0 20 20

. Internal blankets 1.0 1.0 20 20 "to be multiplied times the calculated value.

b to be added in quadrature with uncertainties from other sources.

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Bias Factors and Uncertainties for Sodium-void React.vity in CRBR Calculational Bias Factora Uncertainty,bg Zone BOC-1 EOC-4 BOC-1 EOC-4 Central core 1.0 0.82 10 6 External core 1.0 1.0 10 10 Axial blankets 1.0 1.0 20 20 Internal blankets 1.0 1.0 20 20 a

to be multiplied times the calculated value.

b to be added in quadrature with uncertainties from other sources.

4 e

i Additional Uncertainties in CRBR Sodium-void Reactivity

. Uncertaintya ,

Source  % of Total Reactivity BOC-1 EOC-4 Fuel pins instead of plates 0 0 4 Sequence of voiding 3.5 3.5 Temperature distribution 2.5 2.5 Fission products 0 3.0 a

To be added in quadrature with the values of

" experimental" uncertainty.

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a Best Estimate Sodium Void Reactivity Worths ($)b ,

BOC-1 EOC-4 Driver Assemblies Core -

0.256 1.528 Lower Axial Blanket -0.225 -0.160 Upper Axial Blanket -0.177 -0.177

Total -0.146 1.191 Internal Blanket Assemblies Core 1.381 1.593 Lower Axial Extension 0.008 -0.020 Upper Axial Extension -0.007 -0.006 Total 1.382 1.567 a

Void Flowing Sodium (81.8% driver, 72.6% Blanket) b

= .0032 4

e 9

I i

! FUEL REMOVAL AND ENERGETICS POTENTIAL IN CONNECTION WITH MELT-0VT/ ANNULAR POOL PHASE e

PRESENTED BY:

MICHAEL EPSTEIN FAUSKE t. ASSOCIATESs INC.

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QUESTIONS CS760.178B5, -C.6, -C7

-B5, What is the basis for maintaining continuous subtriticali-ty in the high heat loss environment of early melt-out phase?

What are the fuel-losses (quantified), taking into account uncertainties in removal path geometries, driving pressures and freezing mechanisms?

-C6.

What degree of subtriticality is required to prevent pool recriticality from tilermal and fluid dynamics upset conditions? What is your position on the potential for small recriticalities to amplify? What is the Justifica-tion for your position?

i

-C7.

In assessing benign termination from the boiled-up pool, t

Justify the fuel removal mechanisms and rates, in par-ticular, assess the potential for, upper pool sodium entry via rapid condensation of steel vdpor pressure.

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.. l GENERIC ISSUES COVEREll 1.

DEFINITION OF MELT-0UT PHASE.

2.

DURATION OF MELT-0UT PHASE AND SENSITIVITY CONDITIONS (POWER LEVEL).

3.

RECRITICALITY AND RELATED PHENOMENA.

4.

FUEL FREEZING MECHANISMS AND REMOVAL PATHS.

5.

FUEL REMOVAL REQUIREMENTS FOR PERMANENT S ~

6.

SODIUM RE-ENTRY VIA STEEL VAPOR CONDENSATION.

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POOL DEFINITIONS ,

1.

Melt-Out/ Annular Pool Phase -

Merging of molten driver '

fuel assemblies while the inner blanket fuel assemblies remain intact.

2. Large Scale Pool -

Configuration after the melting Of the inner blanket assemblies.

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O Fuel Assemblies O Alternate Fuel-Blanket-Assemblies g Blanket Assemblies g Centrol Assemblies A:

Ilff SCALE OF THE_tlELT-00T/Al#10LAR POOL PHASE: Ball 1

1. POWER LEVEL BOUNDED BY 50% OF NOMINAL TO PRECLUDE RECRITICALITY ON AN ASSEMBLY SCALE.
2. ADIABATIC HEATUP OF INTER BLANKET FUEL ASSEMBLIES:

E0C-4 BOC-1 TIME = 46 SEC 150 SEC

3. MOLTEN DRIVER FUEL ENTERS INNER BLANKET FUEL ASSEMBLIES':

E0C-4 BOC-1 TIME = 35 SEC 46 SEC

4. CHOICE OF THE POWER LEVEL IS NOT IMPORTANT SO LONG AS LARGE l RAMP RATE RECRITICALITIES CAN BE PR"ECLUDED, i -

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NEUTRONIC EVENTS DURING THE MELT-00T/ ANNULAR POOL PHASE

1. }F RECRITICALITIES SHOULD OCCUR THEY ARE MILD AND DO NOT

, AMPLIFY.

2. ASSEMBLY WALL / FUEL MIXING IS MINIMAL DUE TO FUEL CRUSTING AND MELT LAYER STABILITY.
3. MECHANISM (S) FOR SODIUM RE-ENTRY HAS EQI BEEN IDENTIFIED.

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16L ANALYTICAL CONSIDERATIONS; ID vs. 3D

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IERMINATION OEJELI:OllI/mg!LAR POOL PHASE 1,

FUEL REMOVAL PATHS ARE AVAILABLE, 2,

FUEL REMOVAL IS SUFFICIENT TO ASOU CRITI'CALITY EVEN WHEN ASSESSED ELS. WITH C B

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Schematic of Prbna2'y Control Assembly.

4 Indicates niel Melt Path.

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Normal Sodium Out1ct

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" Absorber Bundle at

- - Operational Level Duct -

Mel't'-Thr5'u gh -

, 777771 -l-I Lower Seal Ring Core Midplanc;- --

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l 81 cm - . 7 Cuide Tube Bottom of LABF---l ,

56'cm- l

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,- Low Pressure Vent

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g Kosepiece Orifice 3-  ;

Normal Inlet Flow h} -

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Vent Outlet to Core Barrel Cooling SstmW of SCA .F7ou PcL7:s for F:tc1.

Re.moval (not to scale).

REQUIREMENTS FOR PERMANENT SUBCRITICALITY AD b

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e REACTIVITY LEVELS FOR VARIOUS DISRUPTE6 CORE CONFIGURATIONS AT BOC-1 Case Description of Core Configuration Reactivity ($)

1 43% of total fuel inventory removed from -1.4 the core. The remaining fuel in the annu-lar regions is hoinogenized in the core and fully compacted with IB and CR assemblies intact.

2 Sace as Case 1 except that only 33% of +10.2 total fuel inventory is removed.

3 Same as 2 except fuel boils up with a linear / 3]

uniform void fraction.

4 41% of total inventory removed from core. The -10.5 remaining fuel, the IB and CR (except B C) 4 assemblies are homogenized and fully compact.

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% Driver Fuel Inventory -

l-Upper Axial 1 l Power Level end Time Interval Blanket and Between Melt-Out/ Annular. Pool g

Location Radial Interassembly Control Rod Phase and Homogeneous Fool

, Blanket Gaps Assemblies Phase **

!  ; i .

. 1 1 Carly* < 10% > 40% = 10%

  • i BL Fuel l Removal Based on Rate of Removal = 150 sec 0j Limited Opening is Fuel Melt
in Clad Bkg. Limited ,

C ' - - - - - - - - - -

! Later* = 20% 15% > 40% Time Interval Reduced by 1/4 i l Fuel No fuel Pene- Based on BFM Due to Driver Fuel Penetra-tration into and BOC Gaps tion into Bkt. Assembly I 1 *l Removal UAB - RB only [ ,

= 35 see Early* > 25% > 40%

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, ' Fuel -

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i Removal . Based on Exp.. Rate of Removal 0% = 46 see 10 l Data Limited is Fuel Melt i l 1 Cla'd 'Bkg. Limited C ---------------------------l---------------- - - - - - - - l - - - - - - - -

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Later* > 40% i > 10% > 30% Time Interval Reduced by 1/2

. Fuel Based on BFM Based on BFM Due to Driver Fuel Penetra-

,4 Removal in UAB (25%) and EOC Caps tion into Bkt. Assembly '

I Plus (20%) in * = 23 see -

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to RB  !

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' Relative to the annular pool phase time interval.

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l Defined by loss of inner blanket fuel assemblics structural integrity. .

POTENTIAL FOR LOSS OF FUEL INVENTORY PRIOR TO .

HELT-OUT OF INNER llLANKET ASSEHilLIES L

EFFECT OF SODIUM IMPEDANCE ON FUEL EENETRATION INTO GAPS _

~

~1.

CONDUCTION MODEL:

PENETRATION LENGTH IS REDUCED B MOST 40%.

THIS REDUCTION DOES NOT ALTER THE FUEL REMOVAL INVENTORY.

2.

Butx FREEZING MODEL_:

NO EFFECT ON PENETRATION LENGT O

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RADIAL SHIELO RAD!ilBLANKET 1 A Ok P ACLP)

S CtiOn to Na g Ai Flow at ACLP)

CORE REGION

$ $' . L55tr.'8LY Pi1CH: 12.1 CM ED W Las Y .hh /,Y hkc?Yhhh, '

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I N N N N N N lutEI noault N Sketch Showing the Inicrstitial Gaps Outside and Below the Core Rcgion.

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_ - _ . - - _ . - -.-. _ -. = - . - - - r. - .- - - - -- - .

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CONSIDERATION OF P0OL S0DIUM ENTRY VIA RAPID CONDENSATION OF STEEL VAPOR PRESSURE l

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SUMMARY

RESPONSE TO QUESTIONS 1,

Once molten fuel mild becomes available on on assembly b recriticality events asis, may be possible but they are limited in amplitude and do not amplify, 2.

Multiple paths for fusl time scale, assemblies.

relative to the melt-outremoval of internal blanket are Correspondingly, fuel removal is not overly sensitive to fuel penetration model escape impedances. assumptions and fuel 3.

There is always time for sufficient fuel removal , 1,.e. about 40% of the driver fuel, to achieve permanent cality subtriti prior to loss Of the annular inner blanketer,barri 4.

The accident sequence will terminate benignly without the development of a homogeneous large scale _

phase confined poo as defined in (Ref, QCS760,178BS-1),

  • 5.

Sodium out re-entry on the basis via steel vapor condensation ruled can be of excessive sodium vaporization when llould sodium comes into contact with steel vapor ,

ROLEOFSTRUCTURESDURINGENERGETIC. TERMINATION e INTERNAL STRUCTURES ACT TO ABSORB, PARTITION AND REDUCE THE LEVEL OF CORE EXPANSION FORCES ON THE PHTS BOUNDARY.

e THE UIS PLAYS AN IMPORTANT MITIGATING ROLE VIA BOTH HYDRODYNAMIC AND HEAT TRANSFER OROCESSES e FINITE ELEMENT ANALYSIS INDICATES THAT A FORCE OF 6.5 MILLION LBF IS REQUIRED TO BUCKLE THE UlS SUPPORT COLUMNS, AND THEREBY REDUCE ITS MITIGATING ROLE.

e THE MAJOR UNCERTAINTY IN THE ABOVE ANALYSIS OF UlS

, COLUV.N BUCKLING IS IN THE YlELD STRESS:

-20 TO +100%.

e INTRAASSEMBLY BLOCKAGES IN UCS ARE STRONG RELATIVE TO EXPECTED CORE PRESSURES, WITH THE BLOCKAGE TEMPERATURE THE CONTROLLING FACTOR.

e OVERALL EFFECT OF STRUCTURES IS TO REDUCE THE PHTS

~

LOADS BELOW THOSE CALCULATED VIA AN ISENTROPIC CORE EXPANSION PROCESS.

ENCLOSURE 4 ACTION ITEMS FOLLOWING THE SEPTEMBER 21, 1982 CRBRP/NRC HCDA ENERGETICS MEETING HELD AT ARGONNE NATION AL L ABORATORY The following action items will be completed and submitted to NRC w i th i n two month s.

1. Provide concise statement on TOP Initiating ramp rates.
2. Provide EOC-3 neutronics data (data type transmitted to ANL will suffice).
3. Provide results of SAS sensitivity eval uation of best parameters for L6 and 17 in-pile tests.
4. Provide SAS 3D input deck with SLUMPY parameters used in response to QCS.760.
5. Recalculate plenum fission gas effects f or EOC-4 w i th new sodium void worth.
6. Provide SAS 3D corrections made to complete item 5.
7. Provide TREAT test R-8 fuel pin data.
8. Provide analysis supporting fuel freezing upon entry to inner blanket assemblies.
9. Provide resul ts of the GAP tests being perf ormed at ANL when av ai l abl e.

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