Text

Preliminary Sequoyah Nuclear Plant,Integrated Containment Analysis,Idcor Task 23.1,Final Rept
	ML20108D133
Person / Time
Site:	Sequoyah
Issue date:	12/31/1984
From:	; TENNESSEE VALLEY AUTHORITY
To:	;
References
	NUDOCS 8412110214
	Download: ML20108D133 (250)
	v • d • e

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. .- i.

I SEQUOYAH NUCLEAR PLANT INTEGRATED CONTAINMENT ANALYSIS IDCOR TASK 23.1 . ,g v c_

%l; v FINAL REPORT 's.

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TENNESSEE VALLEY AUTHORITY NUCLEAR ENGINEERING BRANCH KNOXVILLE, TENNESSEE d

DECEMBER 1984 p.: _

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8412110214 841231 PDR ADOCK 05000327

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47g 4.0 Sequences Analyzed m' ate n.

Considerations of the dominant accident sampling sequences leading to potential core damage as given in the draf t report of IDCOR Task 3.2, resulted in six small LOCAs and two transient initiators, comprising 94.4 percent of the likely core damage initiators. These sequences were-developed by reviewing the Sequoyah RSSMAP study with some regrouping of sequences. The AD accident sequence was added to determine the plant response to a 10 inch diameter LOCA. Translation of these sequences into the Sequoyah reference plant input model include the following assumptions:

1. All LOCA sequences incorporate manual reactor coolant pump trip via operator action subsequent to reactor scram.

2. Credit is taken for the full complement of emergency safeguards for accident sequences where they are available unless otherwise specified.

Table 4.0-1 illustrates the status of both primary and containment sys tems for each accident sequence used in the analysis. The sequences analyzed are:

1. SD 2

- Small LOCA with loss of ECCS injection,

2. SH2

- Small LOCA with loss of ECCS recirculation,

3. S2HF - Small LOCA with loss of ECCS and containment sprays in the recirculation mode,

4. TMLB' - Loss of all AC power and auxiliary feedwater,

5. T 23ML

- Transient with loss of auxiliary feedwater and loss of charging pumps, and

6. AD - Large LOCA with loss of ECCS injection.

IDCOR.4 4.0-1 NEB - Nov. 20, 1984

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e 2d$;. -l-PRI M ARY SYSTEMS STATU,.5' S J...O.#

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( EVENT S2H S2D S2HF TMLS' T23ML AD RCP COASTDOWN X X X X X X UPPER HEAD X X X X X X INJ ECTI ON CHARGIN G X X

^

PLMPS SAFETY INJ X X PLMPS RHR PUAPS X X COLD LEG X X X X X X ACCLMULATORS ECCS RECIR C ECCS HT XCHNG N%IN FEEDWATER AUX FEEDWATER X X X X CONTAINMENT SYSTEMS STATUS EVENT S2H S2D S2HF TMLB' T23ML AD AIR RETURN X X X X X FANS SPRAY X X __ . X X X l

SPRAY REClR C X X X X SPRAY HT. XCHNG X X X X I GNIT ORS X X X X X L'

14. O~2

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4.1 Sequence No. 1 - S'2 D d -J 13 4.1.1 Accident Sequence Description S2 D consists of a small LOCA initiator with' subsequent failure of the ECCS in the injection mode. The ECCS continues to be unavailable in the recirculation mode. Containment safeguards systems lice condenser, sprays, air return fans, and Igniters) are available throughout the accident.

4.1.2 Reactor Coolant System Response Upon initiation of a 0.0218 ft2 cold leg break, the reactor is scrammed, followed by reactor coolant pump coastdown and auxiliary feedwater startup at five seconds. Figures C.1-1 through C.1-5 illustrate the variables of ~ interest. Immediately following break initiation, the primary system pressure decreases to approximately 1250 lb/in2a . At 1

this time (approximately 0.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months ) the UHI rupture disk fails and relatively ' cool water injection is initiated. The rate of inventory loss out of the break is partially offset by the injection of UNI water. The primary. system depressurization continues as decay heat is being transferred to the steam generators and lost through the break. This gradual depressurization continues until 0.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months at which time the core begins to uncover. As the water level in the core continues to drop, the o

cladding temperature begins to increase. Approximately 0.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months after core uncovery the metal-water reaction initiates hydrogen generation.

l The primary system pressure continues to decrease as the remaining water from the UHI is injected (UHI water depletes at 2.02 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months ). At approximately 2.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months , the primary system pressure has dropped below the 415 lb/in2 a set point for the cold leg accumulators and cool water injection begins. At the time of injection initiation the reactor vessel IDCOR.4 4.1-1 NEB - Nov. 28, 1984

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water level is about 10 feet which indicates the bottom of the active -

core is uncovered. The ef fect of this " bottom to top " reflood is to

' initially quench the lower nodes of the core. However, this quenching is not maintained and the heat-up of the injected water supplies steam to the cladding-water reaction and hydrogen production is restarted. As t

core nodes reach the melting temperature, the mass of molten core collecting on the-core support increases until about 110,000 lbe (40 percent of the original core mass) have accumulated at 2.80 hours9.259259e-4 days 0.0222 hours 1.322751e-4 weeks 3.044e-5 months . At this time, the lower core support plate fails and the molten core material falls into the lower plenum of the reactor vessel.

Approximately one minute later (2.81 hours9.375e-4 days 0.0225 hours 1.339286e-4 weeks 3.08205e-5 months ), the molten core material fails one of the penetrations in the bottom of the vessel and the melt is discharged through the hole into the reactor cavity. Following the molten core, the remaining hydrogen, steam, _ and water is discharged into the cavity along with the remaining accumulator water. The core nodes remaining in the vessel continue heating adiabatically. As each node reaches 5144 F it then falls into the cavity. The corium discharge rate af ter vessel failure decreases with the final core node reaching the melting temperature at 7.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months . Total hydrogen production from in-vessel Zirealoy oxidation is 660 lbs. The average rate is 0.10 lb/sec and the reaction is equivalent to a total core average clad oxidation of 32 percent.

4.. 3 Containment Response Inunediately following the accident initiation, the lower compartment pressurizes as RCS inventory is discharged. At 64 seconds the containment spray pressure set point fs L reached. The containment sprays take suction from the RWST until recirculation restignment occurs at 0.4 IDCOR.4 4.1-2 NEB - Nov. 28, 1984 I

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E 5 -

hours. At 2.81 hours9.375e-4 days 0.0225 hours 1.339286e-4 weeks 3.08205e-5 months the vessel fails causing a pressure spike to about 21.0 lb/in2 a The available air return fans, ice, and containment sprays rapidly decrease the pressure to approximately 18 lb/in2 a Since the ice has not been depleted at this time, the temperature Pressure response in the upper compartment remains relatively constant.

suppression is ef fective as anticipated. As the ice continues to melt and RCS inventory is lost from the break, the water level in the lower compartment exceeds- the necessary curb height required for spilling water into the cavity at approximately 0.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . Therefore, by the time reactor vessel failure occurs, the cavity is flooded. This flooded condition limits core-concrete ablation to the " jet" attack resulting in a 0.14 f t penetration depth. The flooded cavity results in inssediate quenching of the corium.

The remaini,ng ice mass at time of vessel failure is approximately 9.1x105 lbs (about 57 percent melted). At 4.92 hours0.00106 days 0.0256 hours 1.521164e-4 weeks 3.5006e-5 months all of the ice has melted and containment pressurization begins. Following ice depletion, the ice condenser and ice condenser upper plenum temperatures immediately increase to approximately the lower compartment temperature.

The containment sprays continue to remove heat from the containment atmosphere with the continued molten corium discharge from the vessel and the decay heat from quenched debris generating steam. This heat removal rate matches the decay heat at approximately 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months when the containment pressure reaches about 20.5 lb/in2 a Afterward, the containment spray heat removal rate exceeds that of decay heat and the containment pressure continues to decrease., thus precluding containment failure.

4.1-3 NEB - Nov. 20, 1984 IDCOR.4

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S2D U1MAAP -

1 i SEC HR EVENT DESCRIPTION CODE l

0.0 0.00 REACTOR SCRAM '

13 I i 0.0 0.00 LETDOWN FLOW OFF 46 O0 0.00 AUX FEEDWATER ON 154

0.0 0.00 MSIV CLOSED 156 l 0.0 0.00 PS BREAK FAILED 209 O.0 0.00 HP1 FORCED OFF 216

. 0.0 0.00 LPI FORCED OFF ,, ,

217 0.0 0.00 MANUAL SCRAM 227

! 0.0 0.00 CHARGING PWPS FORCED OFF 232

! 0.0 0.00 MAKEUP SWITCH OFF 242 0.0 0.00 -LETDOWN SWITCH OFF 243

!, ' 60.5 .02 MAIN COOLANT P W S OFF 4

.02 MCP SWITCH OFF OR Hi-VIBR TRIP 4

60.5 215 *

63.7 .02 CONTMT SPRAYS ON 103

1466.3 .41 RECIRC SYSTEM IN OPERATION . 181 l 1466.3 .41 RECIRC SWITCH: MAN ON 220 2 1483.9 .41 CH PUW S INSUFF NPSH 183 1483.9 .41 HPI PUWS INSUFF NPSH 185 2945.5 .82 FP RELEASE ENABLED 14 i 4597.5 1.28 BURN IN PROGRESS IN 1/C UPPER PLENW 141 j- 5122.7 1.42 BURN IN PROGRESS IN UPPER O@T 102 5186.7 1.44 BURN IN PROGRESS IN ANNULAR CW T 122

5545.2 1.54 BURN IN PROGRESS IN LOWER CW T 75 5629.1 1.56 NO BURN IN LOWER CW T . , . . c. . 75 j 7281.5 2.02 UHI ACCW EWTY 190 i 7774.8 2,16 BURN IN PROGRESS IN LOWER CW T. '

8441.8 2.34 NO BURN IN LOWER CW T 75

- 10037.3 .

2.79 SUPPORT PLATE FAILED 2

! 10100.4 2.81 RV FAILED 3 l 10115.5 2.81 BURN IN PROGRESS IN LOWER CWT 75 ,

i 10191.8 2.83 NO BURN IN 1/C UPPER PLENW 141

{ 10195.2 2.83 BURN IN PROGRESS IN 1/C UPPER PLENW 141

. 10199.3 2.83 ACCWULATOR WATER DEPLETED 188 10207.0 2.84 NO BURN IN LOWER CW T 75

! 10210.8 2.84 NO BURN IN I/C UPPER PLENW 141 j' 10213.8 2.84 BURN IN PROGRESS IN I/C UPPER PLENW 141 I

! 4.1-4 i

,,.-s-_---.,- . . _ - - _ , , - . _ _ _ _ _ . _ . _ , , . - , _ , . . ~ . . . _ _ , _ , , , . _ _ _ _ . . . _ _ .--- - ------

TABIL 4.1 rl DW* d*

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S2D U1MAAP -

CONT.

SEC HR EVENT DESCRIPTION CODE 10245.0 2.85 NO BURN IN t/C UPPER PLENUM 141 10247.3 2.85 NO BURN IN UPPER CW T 102 10251.5 2.85 BURN IN PROGRESS IN I/C UPPER PLENW 141 10261.4 2.85 BURN IN PROGRESS IN UPPER CW T 102 11514.8 3.20 NO BURN IN UPPER CW T 102 11554.3 3.21 BURN IN PROGRESS IN UPPER CW T 102

. 11594.0 3.22 NO BURN IN UPPER CW T 102 11768.8 3.27 BURN IN PROGRESS IN UPPER CWT 102 11813.5 3.28 NO BURN IN UPPER CW T 102 11956.2 3.32 BURN IN PROGRESS IN UPPER CMPT 102 11975.1 3.33 NO BURN IN UPPER CW T 102 12026.6 3.34 NO BURN IN ANNULAR CMPT 122 12042.3 3.35 BURN IN PROGRESS IN ANNULAR CW T 122 -

12120.6 3.37 NO BURN 'IN ANNULAR CWT 122 12126.2 3.37 BURN IN PROGRESS IN ANNULAR CW T 122 12213.8 3.39 No BURN IN ANNULAR CMPT 122 12232.8 3.40 BURN IN PROGRESS IN ANNULAR CW T 122 12406.2 3.45 NO BURN IN ANNULAR CW T 122.

12432.3 3.45 BURN IN PROGRESS IN ANNULAR CMPT 122 12500.7 3.47 NO BURN IN ANNULAR CMPT 122 12505.2 3.47 BURN IN PROGRESS IN ANNULAR CWT 122 12582.2 3.50 NO BURN IN ANNULAR CMPT 122 12593.2 3.50 BURN IN PROGRESS IN ANNULAR CW T 122 12593.2 3.50 NO BURN IN I/C UPPER PLENUM ~141 12604.2 3.50 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12611.9 3.50 NO BURN IN ANNULAR CWT 122

12619.7 3.51 BURN IN PROGRESS IN ANNULAR CW T 122 12624.1 3.51 NO BURN IN 1/C UPPER PLENLM 141 12626.8 3.51 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12711.2 3.53 NO BURN IN ANNULAR CW T 122 I

12711.2 3.53 NO BURN IN 1/C UPPER PI'ENUM 141 i 12764.4 3.55 BURN IN PROGRESS IN ANNULAR CMPT 122 2 12793.1 3.55 BURN IN PROGRESS IN 1/C LdPER PLENW 141

. 12800.1 3.56 NO BURN IN I/C UPPER PLENUM 141

] 141 l 12807.0 3.56 BURN IN PROGRESS IN 1/C IPPER PLENUM i 12842.0 3.57 NO BURN IN I/C UPPER PLENUM 141 l

! 4.1-5 l UL ,

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CON ~~ .

SEC HR EVENT DESCRIPTlON CODE 12856.0 3.57 BURN IN PROGRESS IN 1/C UPPER PLENW 141 12881.9 3.58 NO BURN IN 1/C UPPER PLENUM 141 12916.8 3.59 BURN IN l'ROGRESS IN 1/C UPPER PLENUM 141 12930.9 3.59 BURN IN PROGRESS IN UPPER CW T 102 12951.3 3.60 NO BURN IN UPPER CMPT 102

. 12975.2 3.60 NO BURN IN 1/C UPPER PLENUM 141 12988.9 3.61 BURN IN PROGRESS IN I/C UPPER PLENW 141 13002.5 3.61 NO BURN IN ANNULAR CMPT 122 13002.5 3.61 NO BURN IN 1/C UPPER PLENW 141 13032.5 3.62 BURN IN PFtOGRESS IN ANNULAR CMPT 122 13108.5 3.64 BURN IN PROGRESS IN l/C UPPER PLENW 141 13117.4 3.64 NO BURN IN 1/C UPPER PLENW 141 13135.3 3.65 BURN IN PROGRESS IN /C UPPER PLENW 141 13153.2 3.65 NO BURN IN 1/C UPPER PLENUM 141 13199.8 3.67 NO BURN IN ANNULAR CMPT 122 13211.5 3.67 BURN IN PROGRESS IN ANNULAR CMPT 122 13226.8 3.67 NO BURN IN ANNULAR CMPT 122 13242.0 3.68 BURN IN PROGRESS IN ANNULAR CMPT 122 13257.3 3.68 NO BURN IN ANNULAR CMPT 122 13272.1 3.69 BURN IN PROGRESS IN ANNULAR CMPT 122 13367.5 3.71 NO BURN IN ANNULAR CMPT 122 13398.9 3.72 BURN IN PROGRESS IN ANNULAR CMPT 122 13498.6 3.75, NO BURN IN ANNULAR CMPT 122 13513.5 3.75 BURN IN PROGRESS IN ANNULAR CMPT 122 13526.8 3.76 NO BURN IN ANNULAR CWT 122 13533.6 3.76 BUR. IN PROGRESS IN ANNULAR CMPT 122 13603.3 3.78 NO BURN IN ANNULAR CMPT 122 13620.2 3.78 BURN IN PROGRESS IN ANNULAR CMPT 122 13632.2 3.79 NO BURN IN ANNULAR CMPT 122 13646.8 3.79 BURN IN PROGRESS IN ANNULAR CMPT 122 13796.0 3.83 NO BURN IN ANNULAR CMPT 122 13805.0 3.83 BURN IN PROGRESS IN ANNULAR CMPT 122

. 13821.2 3.8< NO .3 URN IN ANNULAR CMPT 122 13828.6 3.84 BURN IN PROGRESS IN ANNULAR CMPT 122 13863.5 3.85 NO BURN IN ANNULAR CMPT 122

, 13L76.7 3.85 BURN IN PROGRESS IN ANNULAR CMPT 122 t

4.1-6

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TABI.E 4.1_g W[h]5.ls J2

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4dMA*).1 a S2D U1MAAP CONT.

SEC HR EVENT DESCRIPTION CODE 13892.5 3.86 NO BURN IN ANNULAR CMPT 122 13919.9 3.87 BURN IN PROGRESS IN ANNULAR CMPT 122 13994.5 3.89 NO BURN IN ANNULAR CMPT 122 14020.9 3.89 BURN IN PROGRESS IN ANNULAR CMPT 122

, 14040.9 3.90 NO BURN IN ANNULAR CMPT 122

. 14064.9 3.91 BURN IN PROGRESS IN ANNULAR CMPT 122 14166.3 3.94 NO BURN IN ANNULAR CMPT 122 14193.6 3.94 BURN IN PROGRESS IN ANNULAR CMPT 122 14340.4 3.98 NO BURN IN ANNULAR CMPT 122 14397.8 4.00 BURN IN PROGRESS IN ANNULAR CMPT 122 14449.6 4.01 NO BURN IN ANNULAR CMPT 122 14470.3 4.02 BURN IN PROGRESS IN ANNUL,AR CMPT 122 ,

14573.3 4.05 NO BURN IN ANNULAR CMPT 122 14593.3 4.05 BURN IN PROGRESS IN ANNULAR CMPT 122 14607.7 4.06 NO BURN IN ANNULAR CMPT 122 14626.3 4.06 BURN IN PROGRESS IN ANNULAR CMPT 122 14711.4 4.09 NO BURN IN ANNULAR CMPT 122 14718.4 4.09 BURN IN PROGRESS IN ANNULAR CMPT 122 14735.7 4.09 BURN IN PROGRESS IN UPPER CMoT 102 14757.2 4.10 NO BURN IN UPPER CMPT 102 14797.2 4.11 NO BURN IN ANNULAR CMPT 122 14851.3 4.13, BURN IN PROGRESS IN ANNULAR CMPT 122 14912.4 4.14 NO BURN IN ANNULAR CMPT 122 14925.8 4.15 BURN IN PROGRESS IN ANNULAR CMPT 122 14939.1 4.15 NO BURN IN ANNULAR CMPT 122 14957.8 4.15 BURN IN PROGRESS IN ANNULAR CMPT 122 15002.7 4.17 NO BURN IN ANNULAR CMPT 122 15061.9 4.18 BURN IN PROGRESS IN ANNULAR CMPT 122 15134.4 4.20 NO BURN IN ANNULAR CMPT 122 15177.0 4.22 BURN IN PROGRESS IN ANNULAR CMPT 122 15218.4 4.23 NO BURN IN ANNULAR CMPT 122 15314.1 4.25 BURN IN PROGRESS IN ANNULAR CMPT 122 15375.7 4.27 NO BURN IN ANNULAR CMPT 122 15390.8 4.28 BURN IN PROGRESS IN ANNULAR CMPT 122 15439.0 4.29 NO BURN IN ANNULAR CMPT 122 15488.2 4.30 BURN IN PROGRESS IN ANNULAR CMPT 122 4.1-7 4 ___m._ _ _ _ _ _ -_.________ _ _ _ _ _ . - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . - _ . _ _ _ _ . _ _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ . - _ _ _ _ - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ . . - . _ . - - _ _ . _ _ _ _ _ - _ . . _ _ . . _ _ _ _ _ . _ _ _ _ _ _ _

ny m , - - : y1 TABIS 4.1-1 Nb,ifMj[d[3 phkU ty S2D U1MAAP -

CONT.

SEC HR EVENT DESCRIPTION CODE 15554.1 4.32 NO BURN IN ANNULAR CMPT 122 15641.8 4.34 8 URN IN PROGRESS IN ANNULAR CMPT 122-15722.0 4.37 NO BURN IN ANNULAR CMPT 122 15759.5 4.38 BURN IN PROGRESS IN ANNULAR CMPT 122 15825.5 4.40 NO BURN IN ANNULAR CMPT 122 15861.9 4.41 BURN IN PROGRESS IN ANNULAR CMPT 122

. 15941.9 4.43 NO BURN IN ANNULAR CMPT 122 15995.2 4.44 BURN IN PROGRESS IN ANNULAR CMPT 122 p 16007.2 4.45 NO BURN IN ANNULAR CMPT 122 16062.6 4.46 8 URN IN PROGRESS IN ANNULAR CMPT 122 16108.0 4.47 NO BURN IN ANNULAR CMPT 122 16172.7 4.49 BURN IN PROGRESS IN ANNULAR CMPT 122 16213.3 4.50 NO BURN IN ANNULAR CMPT 122 16267.6 4.52 BURN IN PROGRESS IN ANNULAR CMPT 122 16344.4 4.54 NO BURN IN ANNULAR CMPT 122 16355.5 4.54 BURN IN PROGRESS IN ANNULAR CMPT 122 16433.5 4.56 NO BURN IN ANNULAR CMPT 122 16484.7 4.58 BURN IN PROGRESS IN ANNULAR CMPT 122 16539.9 4.59 NO BURN IN ANNULAR CMPT 122 16598.3 4.61 BURN IN PROGRESS IN ANNULAR CMPT 122 16680.0 4.63 NO BURN IN ANNULAR CMPT 122 16739.6 4.65 BURN IN PROGRESS IN ANNULAR CMPT 122 16750.9 4.65 NO BURN IN ANNULAR CMPT 122 16773.6 4.66 BURN IN PROGRESS IN ANNULAR Cl#T 122 16784.9 4.66 NO BURN IN ANNULAR CMPT 122 -

16816.2 4.67 BURN IN PROGRESS IN ANNULAR CMPT 122 16907.2 4.70 NO BURN IN ANNULAR CMPT 122 16926.8 4.70 BURN IN PROGRESS IN ANNULAR CMPT 122 16994.8 4.72 NO BURN IN ANNULAR CMPT 122 17010.8 4.73 BURN IN PROGRESS IN ANNULAR CMPT 122 17018.1 4.73 NO BURN IN ANNULAR CMPT 122 17025.4 4.73 BURN IN PROGRESS IN ANNULAR CMPT 122

, , . 17052.9 4.74 NO BURN IN ANNULAR CMPT 122

~ 17078.6 4.74 BURN IN PROGRESS IN ANNULAR CMPT 122 17085.2 4.75 NO BURN IN ANNULAR CMPT 122 17091.8 4.75 BURN IN PROGRESS IN ANNULAR CMPT 122 4.1-8

.s. o . :. . .

+g e +49

eq ,.s

. S ** 79 rp9

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TABLE 4.1-1 .f' J I g) ,]}]-i zbuL U l_ .1 u s.a.s S2D U1MAAP -

CONT.

SEC HR EVENT DESCRIPT1ON CODE 17131.1 4.76 NO BURN IN ANNULAR O#T 122 17144.0 4.76 BURN IN PROGRESS IN ANNULAR OPT 122 17157.7 4.77 NO BURN IN ANNULAR O#T 122 17198.5 4.78 BURN IN PROGRESS IN ANNULAR OST 122 17215.6 4.78 NO BURN IN ANNULAR OST 122 17251.9 4.79 BURN IN PROGRESS IN ANNULAR O#T 122 17317.5 4.81 NO BURN IN ANNULAR OFT 122 17375.! 4.83 BURN IN PROGRESS IN ANNULAR OST 122 17434.4 4.84 NO BURN IN ANNULAR OPT 122 17448.5 4.85 BURN IN PROGRESS IN ANNULAR O#T 122 17510.7 4.86 NO BURN IN ANNULAR OST 122 17537.2 4.87 BURN IN PROGRESS IN ANNULAR OPT 122 17597.8 4.89 NO BURN IN ANNULAR O#T 122 17614.4 4.89 BURN IN PROGRESS IN ANNULAR OFT 122 17650.4 4.90 NO BURN IN ANNULAR OST 122 17654.6 4.90 BURN IN PROGRESS IN ANNULAR O#T 122 17707.3 4.92 NO BURN IN ANNULAR CMPT 122 17729.6 4.92 ICE DEPLETED 132 4

17731.8 4.93 BURN IN PROGRESS IN ANNULAR CMPT 122 17792.0 4.94 NO BURN IN ANNULAR CMPT 122 gs 2

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4.2 Sequence No. 2 .5 2M 4.2.1 Accident Sequence Description 52H consists of a small LOCA initiator with subsequent failure of the ECCS in the recirculation mode. Emergency core cooling in the injection mode is successful and the containment safeguards systems (ice condenser, i sprays, air return fans, and ignitersi are available throughout the accident.

4.2.2 Reactor Coolant System Response IJpon initiation of a 0.0218 f 2t cold leg break, the reactor is

! scrammed, followed by reactor pump coastdown, and auxiliary feedwater l startup at five seconds. Figures C.2-1 through C.2-5 illustrate the L

variables of Interest. Im:aediately following break initiation, the primary system pressure decreases to approximately 1250 1h/in2,,

During this depressurization period (0.0-0.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months ) high pressure injection charging pumps and safety injection pumps start and UHI initiaties injection at 1255 lb/in2 a This introduction of cool water into the reactor vessel results in initially cooling the primary system water. The primary system water mass continues to increase until 0.37 t

hours when the recirculation witchover point is reached. This increase in primary system inventory and cooling results in decreasing the

! secondary side temperature and pressure. Since the primary system I pressure is continually decreasing af ter unsuccessful recirculation l

switchover, the UHI continues to inject past 0.37 hours4.282407e-4 days 0.0103 hours 6.117725e-5 weeks 1.40785e-5 months . 'This continued

( injection cools the primary and secondary siie until a minimum pressure l

l of about 1000 lb/in2 a is res :hed in the primary system. At this point, the primary side pressure begins to increase due to secondary side l heating. The primary side pressure increase results in term (nation of URI injection. Since heat removal through the break is less than the l

IDCOR.4 4.2-1 NEB - Nov. 23, 1984 i

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Oh,h)34d.h mea decay heat, both primary and secondary pressurize to the secondary side relief valve set point of approximately 1100 lb/in2 a With no more water available for injection, reactor coolant inventory starts decreasing within the primary system. The primary system pressure remains somewhat constant until about 1.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months . At this time, the reactor vessel water level falls below the top of the core and superheated steam begins to exit the core. As the water level in the core continues to decrease, the cladding temperature increases.

Approximately 0.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months after core uncovery, the cladding metal-water reaction initiates significant hydrogen generation. The increasing void in the primary system coupled with the increased flow out of the break causes a depressurization at a relatively constant rate until 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months .

At this time, the pressure has decreased enough for UllI initiation. IntI continues to inject until depletion occurs at about 2.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , after which the injected water is quickly heated to reactor vessel conditions.

During the period 1.5-2.0 hours0 days 0 hours 0 weeks 0 months , the UHI is insuf ficient to quench the fuel resulting in continued hydrogen production.

At s. proximately 2.45 hours5.208333e-4 days 0.0125 hours 7.440476e-5 weeks 1.71225e-5 months , the primary system pressure has decreased to the cold leg accumulator set point (415 lb/in2 a) and bottom-to-top reflood is initiated. This results in providing additional water for steam production and further oxidation of the cladding as indicated by the re-initiation of hydrogen production. Continued accumulator discharge causes the vessel water level and mass to herease as the presaure decreases to approximately 350 lb/in2 a As the core continues to heat up, the first node reaches the melting temperature of 5144 F at 1.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months . Increased heating 2nd node mel* ting results in the molten core co1*ecting on the core support plate until about 110,000 pounds have IDCOR.4 4.2-2 NEB - Nov. 20, 1984

fj : irf t' i.% t y % q .u, d *dib;;i.ld.f Nda.IA ')

accumulated at 3.30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months . At this time, the lower core support plate fails and the molten core material falls into the lower plenum of the reactor vessel. Within one minute, the molten core material fails one of the penetrations in the bottom head of the vessel and the molten core material is discharged through the hole into the reactor cavity.

Following the molten core, the remaining hydrogen, steam, and water is discharged into the cavity along with the remaining accumulator water.

The core nodes remaining in the vessel continue heating adiabatically with each node draining into the reactor cavity when it reaches 51440F.

The corium discharge rate af ter vessel failure decreases, with the final core node reaching the melting temperature at 8.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . A total hydrogen mass of 680 lbs is generated with an average hydrogen produce. ion rate of 0.09 lb/sec. This corresponds to an overall Zircaloy clad oxidation of 33 percent.

4.2.3 Containment Response Immediately following the accident initiation, the lower compartment pressurizes as RCS inventory is discharged. At 65 seconds, the pressure set point for the containment spray is reached. The containment sprays take suction from the RWST until the recirculation alignment occurs ac 0.37 hours4.282407e-4 days 0.0103 hours 6.117725e-5 weeks 1.40785e-5 months . At this point the sprays recirculate water from the containment sump. At 3.31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months when the vessel fails the lower compartment p r e.e eu re increases to about 21.5 lb/in2 a However, the air return fans, containment spraf s, and available ice reduce this pressure to approximately 18 lb/in2 a The water 1cvel in th Iwar compartment exceeds the necessary curb height required for spilling wster into the cavity at approximately 0.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . There fore, by the time the reactor vessel failure occurs, the cavity is flooded. This flooded condition IDCO'i.4 4.2-3 NEB - Nov. 28, 1984

, . y.v. , y n . . , ., ,. , .. .

.w!

! b $NJd, ' .fd[$S$ J limits core-concrete ablation to the jet attack only resulting in a 0.15 f t penetration depth. The flooded cavity results in the immediate quenching-of the corLua.

The Ice remaining at the time of vessel failure is approximately 5.75x105 lbs. At 4.55 hours6.365741e-4 days 0.0153 hours 9.093915e-5 weeks 2.09275e-5 months all the ice has been melted and the l containment pressure rapidly increases due to loss of the passive ice heat sink. The containment sprays continue to remove heat from the contsinment atmosphere, but lag the input decay heat energy until 7.0 hours0 days 0 hours 0 weeks 0 months , at which time the containment pressure of about 20 lb/in2, is reached. Af terward, the containement spray heat removal rate r exceeds that of dec.ay heat and the containment pressure continues to I

decrease, thus precluding containment failure.

i 1

i J

l IDCOR.4 4.2-4 NEB - Nov. 20, 1984 i

)

k

TABLE 4.2-1 S2H U2MAAP -

q.;s m.n- ,$ d b a l' WAND SEC HR EVENT DESCRIPTION CODE 0.0 0.00 REACTOR SCRAM 13 0.0 0.00 LETDOWN FLOW OFF 46 0.0 0.00 AUX FEEDWATER ON 154 0.0 0.00 MSIV CLOSED 156 0.0 0.00 PS BREAK FAILED 209 0.0 0.00 MANUAL SCRAM 227 0.0 0.00 MAKEUP SWITCH OFF 242 '

0.0 0.00 LETDOWN SWITCH OFF 243 47.6 .01 CHARGING PLUPS ON 11 61.1 .02 MAIN COOLANT PLMPS OFF 4 61.1 .02 MCP SWITCH OFF OR Hi-VIBR TRIP 215 64.9 .02 CONTMT SPRAYS ON 103 160.3 .04 HPI ON 5 1342.3 .37 HPl OFF 5 1342.3 .37 CHARGING PLMPS OFF 11 1342.3 .37 RECIRC SYSTEM IN OPERATION 181 1342.3 .37 HPI FORCED OFF 216 1342.3 .37 LPI FORCED OFF 217 1342.3 .37 RECiRC SWITCH: MAN ON 220 1342.3 .37 CHARGING PUMPS FORCED OFF 232 1354.9 .38 CH PLMPS INSUFF NPSH 183 1354.9 .38 HPl PLMPS INSUFF NPSH 185 4442.3 1.23 FP RELEASE ENABLED 14 5818.5 1.62 BURN IN PROGRESS IN l/C UPPER PLENUM 141 6294.7 1.75 BURN IN PROGRESS IN LOWER CMPT 75 6426.6 1.79 BURN IN .'ROGRESS IN UPPER CMPT 102 6493.3 1.80 BURN IN PROGRESS IN ANNULAR CMPT 122 6601.6 1.83 NO BURN IN LOWER CMPT 75 7213.5 2.00 BURN IN PROGRESS IN LOWER CMPT 75 7280.2 2.02 NO BURN IN LOWER CMPT 75 8400.1 2.33 UHI ACCUA EMPTY 190 9449.7 2.62 BURN IN PROGRESS IN LOWER CMPT 75 9895.2 2.75 NO BURt. IN LOWER CMPT 75 10234.8 2.84 BURN IN PROGRESS IN LOWER CMPT 75 10458.2 2.91 NO BURN IN LOWER CVPT 75 11771.0 3.27 BURN IN PROGRESS IN LOWER CMPT 75 4.2-5

*A., . . ..

s ,

3 .

I

-] 3

w m ' 5.L mNTT^. \ -

S2H U2MAAP - s

\

SEC HR : EVENT DESCRIPTION CODE l yJ 11868.9 3,30 SUPPORT PLATE FAILED ~ 2' %, L

\

l 11915.4 3.31 NO BURN IN LOWER CMPT 75 N 11927.3 11936.7 3.31 3.32 RV FAILED BURN,IN PROGRESS IN LOWER CMPT.. -

3' 75

[" ', . '

12021.4 3.34 ACCWULATOR WATER DEPLETED, s 'M 188 ,,

12051.6 3.35 NO BURN IN UPPER OPT 102 ._ .

12058.4 3.35 NO BURN IN LOWER CMPT 75 12062.9 3.35 NO BURN IN 1/C UPPER PLENW 14,1 \

12063.8 3.35 8 URN IN PROGRESS IN I/QUPPER PLENW 141 > _,

12079.5 3.36 NO BURN IN' 1/C $PPER PLENW ~,r -

141 12084.9 3.36 8 URN IN PROGdESS IN 1/C UPPER"PLENLM \

141' 12105.7 3.36 8 URN IN PROGRESS IN NPPE'R CMPT 102 s ,

13429.2 3.73 NO EURN,JJN,UFPER CNFT - i 102 s 7'

13523.7 3.76 8 URN INs PROGRESS IN UPPER OqT 102 13550.7 3.76, NO BURN Ifl UPPER CMPT 102 ?. , ,,

13581.0 3.77 BURN IN PROGRESS IN UPPER CMPT 102 .

l 13597.7 3.78 NO BURN IN' UPPER CMPT

~102 13599.0 3.78 BURN IN Pl< OGRESS IN UPPER CMPT 102 13647.7 3.79 NO' BURh IN UPPER OPT . 102 ,

~

l 13685.1 3.80 NO BURN IN ANNULARsCMPT s 122 .

13722.7 3.81 BURN IN PROGRESS IN ANNULAR iMPT 122 13784.0 3.83 .NO BURN IN' ANNULAR CMPT

s 122.

13853.5 3.85, BURN IN PROGRESS IN ANNULAR CMPT J 2,2 g. ..

13943.6 3.87 NO BURN IN ANNULAR CMPT ' ,'122 ',

N-

! 13951.0 3.88 8 URN -f N PROGRESS IN ANNULAR Cf.FT , 122 ..

l 14097.5 3.92 NO'8 URN IN ANNULAR OST. , ,.

127[ >,

14153.4 3.93 BURN IN PROGRESS UN ANNULAR CWT h 1'22 ^'

l '

14165.3 3.93 NO BURN IN ANNULAR CMPT 1 122

y , s 14182.3 3.94 BURN IN PROGRESS IN ANNULAR CMPT 's 122' '

14260.0 3.96. NO BURN IN' ANNULAR CMPT Sox, N122 s .

14204.6 3.97 BURN IN PROGRESS IN ANNULAR OST.. N .122' 14301.6 3.97 NO BURN IN ANNULAh CMPT \ -

122. '

l 14307.1 3.97 BURN IN PROGRESS IN ANNULAR CMPT , 127 ' i l 14380.4 3.99 NO BURN IN ANNULAR CMPT ' 122 1 14388.2 4.00 BURN IN PROGRESS IN ANNUL'AR CMPT j221 14488.5 4.02 NO BURN IN ANNULAR CNPT'N- s 122

%+

?

4.2-6 -

. _ . _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ . _ _ _ . . . _ . _ _ _ _ _ _ _ _ _ . _ _ _ _ _ . _ . _ _ _ _ _ ...___l..___-__ _ _

.. , .. r ., ,

. , g b d: ;[ il $1 S2H U2MAAP

- CONT.

CODE SEC HR EVENT DESCRIPTION 122 14521.7 4.03 BURN IN PROGRESS IN ANNULAR O/PT 102 14638.4 4.07 BURN IN PROGRESS IN UPPER CMPT 102 14665.2 4.07 NO BURN IN UPPER CMPT 122 14703.1 4.08 NO BURN IN ANNULAR CMPT 122 14775.6 4.10 BURN IN PROGRESS IN ANNULAR O/PT 122 14783.8 4.11 NO BURN IN ANNULAR CMPT 122

. 14792.0 4.11 BURN IN PROGRESS IN ANNULAR CMPT 122 14808.4 4.11 NO BURN IN ANNULAR O/PT 122 14840.5 4.12 BURN IN PROGRESS IN ANNULAR O/PT 122 14892.9 4.14 NO BURN IN ANNULAR CMPT 141 14926.2 4.15 NO BURN IN I/C UPPER PLENUM 141 14939.6 4.15 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 14959.6 4.16 NO BURN IN 1/C UPPER PLENLM 122 14981.1 4.16 BURN IN PROGRESS IN ANNULAR O/PT 141 14994.4 4.17 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 .

15075.8 4.19 NO BURN IN 1/C UPPER PLENUM 141 15084.4 4.19 BURN IN PROGRESS IN I/C UPPER PLENLM 141 15133.8 4.20 NO BURN IN I/C UPPER PLENUM 122 15152.7 4.21 NO BURN IN ANNULAR O/PT 122 15200.3 4.22 BURN IN PROGRESS IN ANNULAR CMPT 122 15288.8 4.25 NO BURN IN ANNULAR CMPT 122 15324.8 4.26 BURN IN PROGRESS IN ANNULAR CMPT 122 15392.6 4.28 NO BURN IN ANNULAR CMPT 122 15481.1 4.30 BURN IN PROGRESS IN ANNULAR O/PT 122 15558.2 4.32 NO BURN IN ANNULAR CMPT 122 15575.6 4.33 BURN IN PROGRESS IN ANNULAR CMPT 122 15672.1 4.35 NO BURN IN ANNULAR CMPT 122 15680.5 4.36 BURN IN PROGRESS IN ANNULAR O/PT 122 15765.2 4.38 NO BURN IN ANNULAR O/PT 122 15779.4 4.38 BURN IN PRCGRESS IN ANNULAR CVPT 122 15991.1 4.44 NO BURN IN ANNULAR CVPT 122 16007.5 4.45 BURN IN PROGRESS IN ANNULAR CMPT 122 16020.2 4.45 NO BURN IN ANNULAR O/PT 122 16032.8 4.45 BURN IN PROGRESS IN ANNULAR CMPT 122 16230.2 4.51 NO BURN IN ANNULAR O/PT 122 16241.9 4.51 BURN IN PROGRESS IN ANNULAR O/PT 4.2-7 a.. . . .-

4 9 m t.t 4.2-1 "4

.[dkUhJdsuJ;p

! M '",n p3 ,

S2H U2MAAP -

CONT.

f SEC HR EVENT DESCRIPTION CODE 16256,1 4.52 BURN IN PROGRCSS IN UPPER CMPT- 102 16276.2 4.52 NO BURN IN UPPER CMPT c 102 16325.3 4.53 NO BURN IN ANNULAR CMPT 122 16329.2 4.54 BURN IN PROGRESS IN ANNULAR CMPT 122 16373.9 4.55 ICE DEPLETED 132 16387.7 4.55 BURN IN PROGRESS .IN UPPER CMPT 102 16407.7 4.56 NO BURN IN UPPER CMPT. 102 16440.1 4.57 NO BURN IN ANNULAR CMPT 122 4

, h

.I s

b

?

s8 f

4.2-8

. e. . - - . .

- . . r-.- - - - . - - ., --

, , , , - .,n- . , , , , , , - - -, - . , , - - . , , - . . , - - . . , , . - , ,

O e t 5 . ,y, ,

4.3 Sequence No.'3 - S HF , N. #ddi G 2

4.3.1 Accident Sequence Description S2 HF consists of a small LOCA initiator with subsequent failure of the ECCS and containment spray system in the recirculation mode. Emergency core cooling and containment sprsys are available during the injection phase only and the containment safeguards systems (ice condenser, air return fans, and igniters) are available throughout the accident.

The following sections will present two scenarios for this accident l

sequence. The first sequence (4.3.2, 4.3.3) postulates that the drains i between the upper and lower compartments are either closed or blocked resulting in the spray water accumulating in the refueling pool thus preventing the normal flowback from the upper compartment to the lower cempartment sump. The second sequence (4.3.4, 4.3.5) presented pcstulates an equipment failure preventing the accumulated water in the lower compartment sump from being recirculated back into the upper compartment.

4.3.2 Reacte Coolant System Response (Drains Blocked)

Upon initiation of a 0.0218 ft2 cold leg break, the reactor is scrammed, followed by reactor pump cesstdown and auxiliary feedwater startup at five seconds. Figures C.3-6 through C.3-10 illustrate the variables of interest. Immediately following break initiation, the l prima.f system pressure drops to saturation pressure followed by the initiation of ECCS injection at 0.01 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months to replace the mass of primary coolant lost out of the break. The ECCS supplies water to the RCS between the time of 0.01 and 0.37 hours4.282407e-4 days 0.0103 hours 6.117725e-5 weeks 1.40785e-5 months . During this time period, the RCS pressure decreases at a slower rate. The UHI begins to inject water IDC0R.4 4.3-1 NES - Nov. 28, 1984

-_m.m.m_ - -

7' " l1 'O 7 p - + ~ S rp J./

p p : ; J; gbh A41 ig y,., .

when the primary system pressure drops below 1255 lb/in2 a This addition of cool water depresses the primary system pressure to a minimum of about 1000 lb/in 2a at about 0.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months af ter which the reactor coolant pressure and temperature increases due to the heat transferred from the secondary side. Continued loss of primary system inventory leads to core uncovery at 1.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months accompanied by initiation of the-cladding metal-water reaction producing hydrogen at a significant rate around 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months . Total hydrogen production is 680 lbs at an average rats of 0.10 lbs/sec. This corresponds to an average clad oxidation of 34 percent. At approximately 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months the primary system pressure decreases below 415 lb/in2 a and the cold leg accumulators begin to' dump water into the reactor vessel. The core continues to heat up until sufficient molten fuel accumulates leading to failure of the core support plate. The molten corium fails the support plate at approximately 3.34 hours3.935185e-4 days 0.00944 hours 5.621693e-5 weeks 1.2937e-5 months . At'3.35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months , the vessel fails and the remaining water, hydrcgen, accumulator water, and molten corium is discharged into the cavity region.

4.3.3 Containment Response'(Drains Blocked)

Immediately following the accident initiation, the lower compartment pressurizes as the RCS inventory is discharged. At 65 seconds the pressure set point for the containment spray is reached. The containment spray tanes suction from the RWST until recirculation switchover -is attempted unsuccessfully at 0.38 hours4.398148e-4 days 0.0106 hours 6.283069e-5 weeks 1.4459e-5 months . At 3.35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months the vessel fails and the containment pressure increases to about 25 lb/in 2a. The forced circulation of the air return fans and remaining ice reduce the pressure to approximately 21 lb/in a. 2 At the time of vessel failure, the water level in the lower compartment is approximately 9 feet, which IDCOR.4 4.3-2 NES - Nov. 28, 1984

_ **G F1 R ?s .

1 s !v o j ':

. f tg, ., g,/

3,,

1_ ,,u an.:.n*dw. .

is less than ' the 10 feet necessary for spillover into the esvity.

Although the containment sprays have delivered all the RWST water prior to recirculation rwitchover at 0.38 hours4.398148e-4 days 0.0106 hours 6.283069e-5 weeks 1.4459e-5 months , all of this inventory is trapped in the upper compartment due to the failure to remove upper to j' lower compartment drain plugs. Therefore, the molten corium is released ;

3 into a dry cavity. Immediate concrete ablation occurs due to " jet"

~

attack during the corium blowdown, resulting in an initial penetration depth of about 0.3 feet.

Following reactor vessel failure, the water level in the lower compartment increases due to accumulation from the melted ice but never - l reaches the necessary 10 foot spillover height. Therefore, once the water discharged during vessel blowdown (cold leg accumulators and remaining vessel inventory) is evaporated by decay heat, the corium in the remetor cavity reheats and thermally attacks the concrete basemat

~

generating noncondens:'ble gases. The mass of ice remaining at the time of vessel failure is approximately 5.75x105 lbs. The air return fans in conjunction with the remaining ice provide containment pressure suppression until 3.81 hours9.375e-4 days 0.0225 hours 1.339286e-4 weeks 3.08205e-5 months , at which time all the ice has melted. With no method of removing decay heat from the containment, and the continued

, generation of noncondencible gases from the core-concrete attack, the i

containment failure pressure of 65 lb/in a2 is reached at 25.93 hoces.

At this time, the containment depressurizes through the assumed 0.02 l

ft2 containment failure hole.

4.3.4- Reactor Coolant Svstem Response (Drains Open) 2 Upon initiation of a 0.0218 ft cold leg break, the reactor is scrammed, followed by reactor pump coastdown and auxiliary feedwater IDCOR.4 4.3-3 NEB - Nov. 28, 1984 t

l l

a '*

'n,w.

e ey.y~n r fq -' : ,13,,2 >MJ 4 d 2 - .

~

,f m.m.Mus3SUj.

startup at five seconds. Figures C.3-1 through C.3-5 illustrate the variables of interest. Immediately following break initiation, the primary ,ystem pressure drops to saturation pressure followed by the initinion of ECCS injection at 0.01 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months to replace the mass of primary coolant lost out of the break. The ECCS system supplies water to the RCS between the time of 0.01 and 0.38 hours4.398148e-4 days 0.0106 hours 6.283069e-5 weeks 1.4459e-5 months . During this. time period, the RCS pressure decreases at a slower rate. The UHI begins to inject water when the primary system pressure drops below 1255 lb/in2 a This addition of cool water depresses the primary system pressure to a minimum of about 1000 lb/in2a at about 0.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months af ter which the reactor coolant pressure and temperature increases due to the heat transferred ,

from the secondary side. Continued loss of primary system inventory leads to core uncovery at 1.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months accompanied by initiation of the

cladding metal-water reaction producing hydrogen at a significant rate aro+ad 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months . Total hydrogen production is 700 pounds with an average rate of 0.10 lbs/sec, which corresponds to an average clad oxidation of 35 percent. At approximately 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months the primary system pressure decreases below 415 lb/in2 a and the cold leg accumulators begin to dump water into the reactor vessel. The core continues to ' at up until suf ficient molten fuel accumulates to failure of the core support plate with molten corium flowing into the lower plenum. at approximately-3.30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months . Vessel failure occurs about one minute later and the remaining water, hydrogen, accumulator water, and molten corium is discharged into the reactor cavity region.

4.3.5 Containment Response (Drains Not Blocked)

In: mediately following the accident initiation, the lower compartment pressurizes as the RCS inventory is discharged. At 65 seconds the

IDCOR.4 4.3-4 NEB - Nov. 28, 1984 i

0 h ub a pressure setpoint for the. containment spray is reached. The containment

-spray takes suction from the RWST until recircualtion switchover is attempted unsuccessfully at 0.37 hours4.282407e-4 days 0.0103 hours 6.117725e-5 weeks 1.40785e-5 months . At 3.31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months the vessel fails causing a containment pressure increase to 28 lb/in2a. The forced circulation of the air return fans and the remaining ice reduce the pressure to approximately 18 lb/in2 a '. The water level in the lower compartment has equaled the height required for spillover-into the cavity at 0.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . Therefore, the molten corium is release into a flooded cavity. Immediate concrete ablation occurs due to " jet" attack during

. the corium blowdown, resulting in an initial penetration depth of 0.15 feet. However, the debris is innediately quenched, halting any more concrete attack and the containinent pressure ren; sins low until the ice melts at 4.36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months . Subsequently, with no method for removing decay heat, the containment pressurizes due to steam formation and fails .at 9.54 hours6.25e-4 days 0.015 hours 8.928571e-5 weeks 2.0547e-5 months . At this time, the containment - depressurizes through the .

assumed 0.02 ft2 failure hole.

t 1

IDCOR.4 4.3-5 NEB - Nov. 28, 1984

S2HF U7MAAP (.Mm RocWO)

PR(())QM"D'f ~

SEC HR EVENT DESCRIPTION CODE 0.0 0.00 REACTOR SCRAM 13 0.0 0.00 LETDOWN FLOW OFF 46 0.0 0.00 AUX FEEDWATER ON 154 0.0 0.00 MSIV CLOSED 156 0.0 0.00 PS BREAK FAILED 209 0.0 0.00 MANUAL SCRAM 227 0.0 0.00 MAKEUP SWITCH OFF 242 0.0 0.00 LETDOWN SWITCH OFF 243 47.6 .01 CHARGING PUMPS ON 11 61.1 .02 MAIN COOLANT PLAPS OFF 4 61.1 .02 MCP SWITCH OFF OR Hi-VIBR TRIP 215 64.9 .02 COtGMT SPRAYS ON 103 160.3 .04 HPI ON 5 1356.8 .38 HPI OFF 5< >

1356.8 .38 CHARGING PUMPS OFF 11 1356.8 .38 COtGMT SPRAYS OFF 103 i 1356.8 .38 HPI FORCED OFF 216 1356.8 .38 LPI FORCED OFF 217 1356.8 .38 SPRAYS FORCED OFF 222 1356.8 .38 CHARG1NG PUMPS FORCED OFF 232 ,

4435.5 1.23 FP RELEASE ENABLED 14 ,

5916.7 1.64 BURN IN PROGRESS IN I/C UPPER PLENUM 141 6312.1 1.75 8 URN IN PROGRESS IN LOWER CNPT 75 6430.8 1.79 BURN IN PROGRESS IN UPPER CNPT ,.

102 ,,

6491.2 1.80 BURN IN PROGRESS IN ANNULAR ChPT 122 6592.4 1.83 NO BURN IN LsWER ChPT 75 8442.7 2.35 UHI ACCUM EMPW 190 9250.4 2.57 BURN IN PROGRESS IN LOWER CMPT 75 9858.8 2.74 NO BURN IN LOWER CNPT 75 11413.3 3.17 BURN IN PROGRESS IN LOWER CMPT 75 11697.7 3.25 NO BURN IN LOWER CNPT 75 11805.4 3.28 BURN IN PROGRESS IN LOWER CMPT 75 11970.6 3.33 NO BURN IN LOWER CNPT 75 12014.3 3.34 SUPPORT PLATE FAILED 2 12077.0 3.35 RV FAILED 3 12129.4 3.37 BURN IN PROGRESS IN LOWER CMPT 75 4.3-6 9 4 W =4

. . - . -.~_.. . ._.- . -. - - __ .- . . . . . - - . . - . . . . . . - . . - - _ - - - - _ . - . . . . .

.;oe.;.u.: y TmE 4.3-1 1 -d Ndd!!b 2U S2HF U7MAAP (ORMN 6MckEO) CONT.

SEC HR EVENT DESCRIPTION CODE 12169.8 3.38 ACCT.MULATOR WATER DEPLETED 188 12261.4 3.41 NO BURN IN 1/C UPPER PLENW 141 12272.7 3.41 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12366.3 3.44 NO BURN IN LOWER CMPT 75 13730.4 3.81 ICE DEPLETED 132 13739.1- 3.82 NO BURN IN I/C UPPER. PLENUM 141 13762.0 3.82 NO BURN IN UPPER CMPT 102 13790.1 3.83 NO BURN IN ANNULAR CMPT 122 31512.0 8.75 8 URN IN PROGRESS IN LOWER CMPT 75 31594.5 8.78 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 31996.0 8.89 BURN IN PROGRESS IN UPPER CMPT 102 32079.5 8.91 BURN IN PROGRESS IN ANNULAR CMPT 122 34034.8 9.47 NO BURN IN LOWER CMPT 75 34104.8 9.47 BURN IN PROGRESS IN LOWER CMPT 75 1 34124.8 9.48 NO BURN IN LOWER CMPT 75 34164.8 9.49 BURN IN PROGRESS IN LOWER CMPT 75 34164.8 9.49 NO BURN IN 1/C UPPER PLENW 141 34184.8 9.50 NO BURN IN LOWER CNPT 75 34184.8 9.50 BURN IN PROGRESS IN 1/C UPPER PLENW 141 34204.8 9.50 NO BURN IN 1/C UPPER PLENUM 141 i 34244.8 9.51 NO BURN IN UPPER ChPT 102 34244.8 9.51 NO BURN IN ANNULAR CMPT 122 93364.4 25.93 CONTMT FAILED 104 t

l .

l 4.3-7 I

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

= ' '-'

pg"g.g,gf

?

S2HF U3MAAP (oWN **) "

SEC HR EVENT DESCRIPTION CODE 0.0 0.00 REACTOR SCRAM 13 0.0 0.00 LETDOWN FLOW OFF 46 0.0 0.00 AUX FEEDWATER ON 154 0.0 0.00 MSIV CLOSED - 156 1 0.0 0.00 PS BREAK FAILED 209' O.0 0.00 MANUAL SCRAM 227

. 0.0 0.00 MAKEUP SWITCH OFF 242 0.0 0.00 LETDOWN SWITCH OFF 243 47.6 .01 CHARGING PUMPS ON 11 61.1 .02 MAIN COOLANT P M S'OFF 4 61,1 .02 MCP SWITCH OFF OR HI-VIBR TRIP 215 64.9 .02 CONTMT SPRAYS ON 103 160.3 .04 HPI ON 5 i 1342.3 .37 HPI OFF 5 ,

1342.3 .37 CHARGING PUMPS OFF 11 1342.3 .37 CONTMT SPRAYS OFF 103

, 1342.3 .37 HPI FORCED OFF 216

. 1342.3 .37 LPI FORCED OFF 217 1342.3 .37 SPRAYS FORCED OFF 222

. 1342.3 .37 CHARGING POSS FORCED OFF 232 4441.5 1.23 FP RELEASE ENABLED 14- i 5798.9 1.61 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 6281.4 1.74 8 URN IN PROGRESS IN LOWER ChPT 75 6420.4 1.78 BURN IN PROGRESS IN UPPER CMPT 102 6486.4 1.80 BURN.IN PROGRESS IN ANNULAR CWT 122 6601.'9 1.83 NO BURN IN LOWER ChPT

^

75

8316.7 2.31 UHI ACCUM ENPTY . 190 9346.3 2.60 BURN IN PROGRESS IN LOWER ChPT 75 9819.3 2.73 NO BURN IN LOWER ChPT 75

9925.4 2.76 BURN IN PROGRESS IN LOWER ChPT 75

j. 10112.0 2.81 NO BURN IN LOWER ChPT 75 l 11764.7 3.27 BURN IN PROGRESS IN LOWER CAPT 75 11868.8 3.30 SUPPORT PLATE FAILED 2 11923.9 3.31 NO BURN IN LOWER CMPT 75 i 11932.7 3.31 RV FAILED 3.

11942.1 3.32 BURN IN PROGRESS IN LOWER CMPT 75 I

4.3-8 l

+ .

.. . - . - - , , - -,,,m.,,, .,,,,,,,,,y,.,_,.---..,..-.m...- . - . . . - - . . ~ , - - , - , . . - , . . _ - . . , . - _ _ , . , - - - - - . . - , _ . - - , _ , . - - , . ~ _ , , ~ - . . . - - . , , -

TABI.E 4.3-1 7:~ 7: .Tl d 5 I[

(ogarN on4 "P:".N'"'}.CONT. }.g'4{.3 j;d

~"

S2HF U3MAAP SEC HR EVENT DESCRIPTION CODE 11951.6 3.32 NO BURN IN LOWER CNPT 75 11965.7 3.32 BURN IN PROGRESS IN LOWER ChPT 75 11989.9 3.33 NO BURN IN 1/C UPPER' PLENUM 141 11991.9 3.33 BURN IN PROGRESS.IN 1/C UPPER PLENUM ~ 141 12028.0 3.34 ACCT.MULATOR WATER DEPLETED 188 12073.1- 3.35 NO BURN IN LOWER CMPT 75 4

, 12077.9 3.35 NO BURN IN UPPER CAPT 102 4 12123.2 3.37 NO BURN IN ANNULAR ChPT 122 12148.2 3.37 NO BURN IN 1/C UPPER PLENUM 141 12158.8 3.38 BURN IN PROGRESS IN 1/C UPPER PLENL.M 141 12230.0 3.40 BURN IN PROGRESS IN UPPER CMPT 102 12286.5 3.41 BURN IN PROGRESS IN ANNULAR CWT 122 13694.1 3.80 NO BURN IN ANNULAR CMPT 122 1

13761.5 3.82 NO BURN IN UPPER ChPT 102 :

13801.5 3.83 BURN IN PkOGRESS IN UPPER CWT 102 13821.0 3.84 NO BURN IN UPPER ChPT 102 13849.8 3.85 BURN IN PROGRESS IN UPPER ChPT 102 13864.8 3.85 NO BURN IN-UPPER CW T 102 13903.9 3.86 BURN IN PROGRESS IN UPPER ChPT 102 13923.9 3.87 NO BURN IN UPPER ChPT 102 14006.0 3.89 BURN IN PROGRESS IN UPPER CW T 102

+

14022.1 3.90 NO BURN IN UPPER CW T 102 14132.4 3.93 NO BURN IN 1/C UPPER PLENUM 141 14183.9 3.94 BURN IN PROGRESS IN UPPER ChPT 102 14206.6 3.95 NO BURN IN UPPER CWT 102 15707.8 4.36 ICE DEPLETED 132 34346.5 9.54 CONTMT FAILED 104

)

i 4.3-9

. w _._ _

._ .~._._._.._._.._.._ _ _. _ _.._._ __.._ ___

I.

h 4.4 Sequence No. 4 - TMLB' hh':

l'd DUbJ 23 id %hb hd 4.4.1 Accident Sequence Description TMLB' consists of a transient sequence initiated by loss of off-site -

AC power with subsequent loss of'on-site AC power. Due to lack of cooling, the reactor coolant pump seals fail resulting in a small LOCA (50 gpm/ pump). In this sequence, several potential sequences are lumped together. These include immediate failure of main and auxiliary feedwater as well as sequences involving no interruption of main feedwater but subsequent failure of the power conversion system and failure of the auxiliary feedwater. For the base case analysis, both main and auxiliary feedwater are both assumed lost at the time of ,

the inittating event. Emergency core cooling, containment sprays, air return fans, and hydrogen igniters are not available due to loss of all AC power.

4.4.2 Reactor Coolant System Response This sequence is initiated by loss of off-site AC power with subsequent loss of on-site AC power, reactor trip, reactor pump coastdown, and loss of both main and auxiliary feedwater. Figures C.4-1 through C.4-5 illustrate the variables of interest. Due to lack of injection and cooling, the reactor coolant pump seals fail at 0.75 hours8.680556e-4 days 0.0208 hours 1.240079e-4 weeks 2.85375e-5 months resulting in a total 200 gal / min leak. The RCS water mass continues to decrease as RCS inventory is depleted through the pump seals. The primary system maintains a relatively constant pressure of 2000 lb/in2a as the steam generators provides a heat sink. However, the steam generators are losing mass through the secondary side relief valves with no make-up from feedwater.

IDCOR.4 4.4-1 NEB - July 11, 1984 l

v

')

L

/67/l 2

,i t

The primary system pressure starts to rapidly increase between 1,4 and 1.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months due to the loss of the secondary side steam generator heat sink. The pressure continues to increase to the set point of the ._

pressurizer relief valves. Continued blowdown to the quench tank results in failure of the tank rupture disk at 1.66 hours7.638889e-4 days 0.0183 hours 1.09127e-4 weeks 2.5113e-5 months . Steam generator dryout also occurs at 1.66 hours7.638889e-4 days 0.0183 hours 1.09127e-4 weeks 2.5113e-5 months . During this time of high pressure RCS blowdown, the water level in the reactor vessel rapidly decreases with

. core uncovery around 2.10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months and initiation of hydrogen production occurring at approximately 2.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months . The total hydrogen production is 590 lbs. at an average rate of 0.14 lbs/sec. This corresponds to an overall oxidation of 30 percent. The primary system continues to remain at high pressure and suf ficient molten corium is accumulated to fail the core support plate at approximately 3.33 hours3.819444e-4 days 0.00917 hours 5.456349e-5 weeks 1.25565e-5 months as evidenced in the vessel pressure spike and slight level swell in the vessel. About one minute later, the vessel fails and the remaining water, hydrogen, ard corium are discharged from the vessel into the cavity at high pressure. Due to the elevated RCS pressure, no water is injected by either UHI or cold leg accumulators until the time of vessel failure.

4.4.3 Containment Response The containment press'ure increases to 17 lb/in2a following failure of

- the pump seals and then increases further to approximately 21 lb/in2 ,

following quench tank rupture disk failure. At 3.35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months the vessel fails, increasing the containment pressure to approximately 30 lb/in ,,2 At the time of vessel failure the water level in the lower compartment is approximately 2.8 feet which is less than the 10 feet necessary for spillover into the cavity. Therefore, the molten corium is released into IDCOR.4 4.4-2 NEB - July 11, 1984

P; 8]L - A] 17. "Sq y, m - v j .. m . _ .;

a dry cavity. ~1amediate concrete ablation occurs due to." jet" attack during the corium blowdown, resulting in an initial penetration depth of about 0.20 feet.

Following reactor vessel failure, the water level in the lower compartment never reaches the necessary 10 foot spillover height.

Therefore, once the water discharged during vessel blowdown (cold leg accumulators and UHI) is evaporated by decay heat, the corium in the reactor cavity reheats and decomposes the concrete, thus generating noncondensible gases. The mass of ice remaining at time of vessel failure is approximately 1.25x10 6 lbs., but this has melted by 5.84 hours9.722222e-4 days 0.0233 hours 1.388889e-4 weeks 3.1962e-5 months . With no method of removing decay heat from the containment, and-the continued generation of noncondensible gases from the corium-concrete attack, the containment failure pressure of 65 lb/in2 a is reached at approximately 27.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . At this time, the containment depressurizes-

^

through the assumed 0.001 f t2 containment failure hole.

i i

IDCOR.4 4.4-3 NEB - July 11, 1984 4

- , . . , . , , , . , , - . ,,,-n,.-.-.,..- . - - . . . , , - ,. - , , - - ---.,.-,c. ,,

,mn . _1 .- 7 m . . - . . . . ; 6

,)

l

" " "1 " *3 TMLB' U4MAAP- -

1 SEC HR EVENT DESCRIPTION CODE l l 0.0 0.00 MAIN COOLANT PWPS OFF 4 O.0 0.00 REACTOR SCRAM . 13 I

0.0 0.00' LETDOWN FLOW OFF 46 0.0 0.00 MSIV CLOSED -

156

0. 0. 0.00 POWER NOT AVAILABLE 205

0. 0' O.00 MAKEUP SWITCH OFF 242

- 0.0 0.00 LETDOWN SWITCH OFF 243

-2717.1 .75 PS BREAK FAILED 209 5970.3 1.66 Q/T RUPTURE DISK FAILED 92 5991.3 1.66 UNBKN S/G DRY 161 5992.3 1.66 BROKEN S/G DRY 151 6789.9 1.89 MCP SWITCH OFF OR HI-VIBR TRIP 215 7546.8 2.10 FP RELEASE ENABLED 14 11984.2 3.33 SUPPORT PLATE FAILED 2

~

12046.4 3.35 RV FAILED 3 12064.2 3.35 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 1

12071.9 3.35 NO BURN IN 1/C UPPER PLENUM 141 12080.5 3.36 BURN IN PROGRESS IN I/C UPPER PLENUM 141 12177.0 3.38 ACCUMULATOR WATER DEPLETED 188 1

12190.8 3.39 NO BURN IN 1/C UPPER PLENLM 141 12192.2 3.39 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12208.1 3.39 NO BURN IN 1/C UPPER PLENUM 141 12215.9 3.39. BURN IN PROGRESS IN 1/C UPPER PLENUM 141

[ 12218.0 3.39 NO BURN IN 1/C UPPER PLENUM 141

!' 12219.6 3.39 BURN IN PROGRESS IN 1/C UPPER PLENW 141 12235.9 3.40 NO BURN IN 1/C UPPER PLENUM 141 12237.0 3.40 BURN IN PROGRESS IN I/C UPPER PLENUM 141 12252.7 3.40 NO BURN IN.l/C UPPER PLENUM 141 12259.5 3.41 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12262.9 3.41 NO BURN IN I/C UPPER PLENW 141 12269.4 3.41 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12271.5 3.41 NO BURN IN I/C UPPER PLENUM 141 12280.2 3.41 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12281.4 3.41 NO BURN IN 1/C UPPER PLENUM 141

! 12284.7 3.41 UHI ACCUM ENPTY 190 2 12286.5 3.41 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 e

4.4 4 1

-- e,n a e-e- .e,--,,--w,,--,-,,,,.,w,,,,e na,,.p. e., ,, -,v,,v-m-,.w,.mm ,,,-,,,,--.,,,n.~, m.__ _ m ng,me, w a w-.-- ,

- .- - - - . _ ~ . . - . - - - . - -

a. .

TABLE 4.4-l'

{ 7 : t -} 7...:

"gg u m . ., .

TMLB' U4MAAP- T6(T".

.SEC HR EVENT DESCRIPTION CODE L 12293.9 3.41 NO BURN IN 1/C UPPER PLENUM 141 12300.7 3.42 . BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12302.B 3.42 NO BURN IN I/C UPPER PLENUM 141

, 12310.6 3.A2 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12312.3 3.42 NO BURN IN 1/C UPPER PLENUM 141 ,

, 12319.5 3.42 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 I' . 12321.0 3.42 NO BURN IN 1/C UPPER PLENUM 141 12329.3 3.42 PURN IN PROGRESS IN 1/C UPPER PLENW 141 12330.6 3.43 NO BURN IN I/C UPPER PLENUM 141 12341.2 3.43 BURN IN PROGRESS IN 1/C UPPER PLENUM 141-12342.6 3.43 NO BURN IN 1/C UPPER PLENUM 141 12352.9 3.43 BURN IN PROGRESS IN l/C UPPER PLENUM 141 12354.4 3.43 NO BURN lN 1/C UPPER PLENUM 141 12361.1 3.43 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 4-12363.0 3.43 NO BURN IN 1/C UPPER PLENW 141 12370.7 3.44 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12372.5 3.44 NO BURN IN 1/C UPPER PLENUM 141 12379.0 3.44 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12381.1 3.44 NO BURN IN 1/C UPPER PLENUM 141 12388.2 3.44 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 4

12390.4 3.44 NO BURN IN l/C UPPER PLENUM 141 12399.1 3.44 BURN IN PROGRESS IN 1/C UPPER PLENUM 141

[ 12401.8 3.44r NO BURN IN 1/C UPPER PLENUM 141 12410.0 3.45 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 ,.

12413.6 3.45 NO BURN IN 1/C UPPER PLENUM 141

. 12479.2 3.45 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12424.8 3.45 NO BURN IN 1/C UPPER PLENUM 141 12433.0 3.45 BURN IN PROGRESS IN 1/C UPPER PLENW 141 12448.6 3.46 NO BURN IN 1/C UPPER PLENUM 141 12453.2 3.46 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12469.4 3.46 NO BURN IN 1/C UPPER PLENW 141 12473.6 3.46 BURN IN PROGRESS IN 1/C UPPER PLENUM 141

, 12489.2 3.47 NO BURN IN 1/C UPPER PLENUM 141 12492.0 3.47 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12507.5 3.47 NO BURN IN 1/C UPPER PLENUM 141 1- 12511.9 3.48 BURN IN PROGRESS IN 1/C UPPER PLENW 141 4

4.4-5

~

.a ,.- . .

.* i

TABLE 4.4-1 'l , J. bsiljgg ?A L1 g lrl TMLB' U4MAAP- CONT.

SEC HR EVENT DESCRIPTION CODE 12527.3 3.48 NO BURN IN 1/C UPPER PLENW 141 12530.3 3.48 BURN IN PROGRESS IN 1/C UPPER PLENW 141 i' 12545.9 3.48 NO BURN IN 1/C UPPER PLENUM 141 12549.7 3.49 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 12565.6 3.49 NO BURN'IN 1/C UPPER PLENUM 141 12571.4- 3.49 BURN IN PROGRESS IN 1/C UPPER PLENUM. 141 l 13258.9 3.68 NO BURN IN I/C UPPER PLENUM 141 21018.1 5.84 ICE DEPLETED 132 38157.3 10.60 BURN IN PROGRESS IN LOWER CMPT 75 38183.7 10.61 NO BURN IN LOWER CMPT 75 38528.8 10.70 BURN IN PROGRESS IN LOWER CAPT 75 38555.2 10.71 NO BURN IN LOWER CMPT 75 3 39111.6 10.86 BURN IN PROGRESS IN LOWER CMPT 75 l 39137.5 10.87 NO BURN IN LOWER ChPT 75

41372.8 11.49 BURN IN PROGRESS IN LOWER CMPT 75 41378.9 11.49 BURN IN PROGRESS IN UPPER CMPT 102

] 41378.9 11.49 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 1 41394.9 11.50 NO BURN IN 1/C UPPER PLENUM 141 2

41398.7 11.50 NO BURN IN LOWER CMPT 75 41400.1 11.50 NO BURN IN UPPER CMPT 102 42362.9 11.77 BURN IN PROGRESS IN LOWER ChPT 75 42389.4 11.77 NO BURN IN LOWER CMPT 75 97695.6 27.14; CONTMT FAILED 104

.~ . . . .

i 4

l l

4.4-6

.~ .

, -n.+ ~..,- , - - - - , . .-,,,,-,.-c- ,.-,-..,,--,,-,-,--n.-.. . . , , - . , - . . - - , , . - - . . . . , - , , . , - , - - - , - , - - - . , - , . - - - . . , - . - , , , - - - , . - - . - , - - - - , , , , ,

i DMWq 17 t m ., , .. ,

0

l Y h ~ $. l ,

4.5 Sequence No. 5 - T23MI' 4.5.1 Accident Sequence Description T23ML e nsists of a transient initiator other than loss of off-site power with automatic reactor trip and loss of main and auxiliary feedwater. AC power is available and, therefore, emergency core cooling and containment safeguards are available throughout the accident.

Although suf fi' ient time exists for operator action, the base case assumes human or equipment failures prevent proper charging and safety system operation. It, therefore, is a very low probability event.

Higher probability sequences are discussed in section 5.0.

4.5.2 Reactor Coolant System Response This sequence is initiated by loss of both main and auxiliary feedwater, followed by reactor trip and reactor pump coastdown.

Figures C.5-1 through C.5-5 illustrate the variables of interest.

Following loss of all feedwater and reactor scram, the primary system pressure decreases momentarily followed by the actuation of the pressurizer heaters which maintain the pressure at approximately 2250 lb/in2. The water level in the pressurizer increases during heat up and volumetric expansion causing the pressurizer to go solid around 1.0 hour0 days 0 hours 0 weeks 0 months after accident initiation.

The primary system pressure starts to increase after 0.95 hours0.0011 days 0.0264 hours 1.570767e-4 weeks 3.61475e-5 months due to the loss of the secondary side steam generator heat sink. The pressure continues to rise to the set point of the presssurizer safety valves.

However, blowdown through these valves decreases primary system inventory and with no makeup available, both the primary system pressure and level begin to decrease. The re fore , the primary system pressure stablizes at IDCOR.4 4.5-1 NEB - Nov. 28, 1984

r. ,

+ . . - w gj.jgd..qpA t0A the PORV set point of 2350 lb/in2 a with continued inventory depletion and core uncovery occurring at 1.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months . As the water level in the core continues to drop, the cladding temperature begins to increase. At approximately 1.9' hours, the metal-water reaction initiates significant hydrogen generation and further core melting. Total hydrogen production

from in-vessel Zirealoy oxiiation is 520 lbs. The average production rate is 0.14 lba/see and the reaction is equivalent to a total core average clad oxidation of 26 percent. The primary system continues to remain at high pressure and suf ficient molten corium is accumulated to

' fail the core support plate at 2.90 hours0.00104 days 0.025 hours 1.488095e-4 weeks 3.4245e-5 months . At 2.91 hours0.00105 days 0.0253 hours 1.50463e-4 weeks 3.46255e-5 months the vessel 1

fails and the remaining water, hydrogen, and corium core discharged from the vessel into the cavity at high pressure.

4.5.3 Containment Response The containment pressure remains at about 15 lb/in2 a until quench tank rupture disk failure at 1.20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months . The containment pressure rapidly increases to 19.5 lb/in a2 but is suppresssed as the containment sprays (actuated at 1.21 hours2.430556e-4 days 0.00583 hours 3.472222e-5 weeks 7.9905e-6 months ), air return fans, and ice are available. The

' containment sprays take suction from the RWST until successful recirculation realignment occurs at 1.60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months . This pressure 2 y,,,,1 suppression reduces the pressure to about 17.0 lb/in , ,,ggi

' failure occurs at 2.91 hours0.00105 days 0.0253 hours 1.50463e-4 weeks 3.46255e-5 months with a corresponding pressure increase to 23 lb/in a2 which is quickly suppressed. As the ice continues to melt and RCS inventory is lost from the pressurizer relief valves, the water level in the lower compartment exceeds the necessary curb height required for spilling water into the cavity at approximately 1.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months . Therefore, when the vessel fails the cavity is flooded. This flooded condition 4.5-2 NEB - Nov. 28, 1984 IDCOR.4

. - . . _ , , ,_ , _ . , - . , ,..__;- _ , , , . , _ _ ,,___,.yx _ _ , . , . ~,-,..-.---,y-

577 ",'] 7 "il ?!.~G ' 7 7 3 3 :l: ideo l dis ] l limits core-concrete ablation to the " jet" attack resulting in a 0.14 i

foot penetration depth. The flooded cavity results in immediate quenching of the corium.

The remaining ice at time of vessel failure is approximately 1.3x106 lbs. At 5.36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months , all of the ice has melted and containment pressurization begins. Following ice depletion, the containment pressure rapidly rises to about 20 lb/in2 a However, the containment sprays continue to remove heat from the containment atmosphere. This heat removal rate matches the heat decay at approximately 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months .

Therefore, the containment spray heat removal rate is more than adequate l to remove decay heat and the containment pressure continues to decrease, thus precluding containment failure.

i 6

IDCOR.4 4.5-3 NEB - Nov. 28, 1984 I

. - . . _ , _ . _ . _ . _ . . . _. ._ _ . - . . , . _ . . , . . _ . , _ _ , _ . _ . . . , , _ . _ _ _ , _ _ . _ ...__._-....m_. - , - _ , , . ,

2] M_:' /' 1.!h]

p, TAnLE 4.5-1

3. ]B,7

!! i T23ML- U5MAAP.-

l

,. SEC HR- EVENT DESCRIPTlON CODE i 0.0 O.00 REACTOR SCRAM 13 0.0 0.00 LETDOWN, FLOW OFF 46 0.0 0.00 MSIV CLOSED 156 4

0.0 0.00 HPI FORCED OFF 216 0.0 0.00 LPI FORCED OFF 217

0.0 0.00 AUX FEED WATER FORCED OFF 224

. 0.0 0.00 MANUAL SCRAM 227 0.0 0.00 MAIN FW SHUT OFF 228 )

0.0 0.00 CHARGING P W S FORCED OFF 232 l 0.0 0.00 MAKEUP SWITCH OFF -

242 O.0 0.00 LETDOWN SWITCH OFF 243 3404.4 . 95 BROKEN S/G DRY 151 i 3404.4 . 95 UNBKN S/G DRY 161 4310.3 1.20 Q/T RUPTURE DISK FAILED 92 4348.8 1.21 MAIN COOLANT P M S OFF 4 4348.8 1.21 MCP SWITCH OFF OR Hi-VIBR TRIP 215 4 4350.9 1.21 CONTMT SPRAYS ON 103 l 5753.7 1.60 RECIRC SYSTEM IN OPERATION 181 5753.7 1.60 REC lRC SWlTCH: MAN ON 220 5765.8 1.60 CH P N S INSUFF NPSH 183 5765.8 1.60 HPI P W S INSUFF NPSH 185 f 6163.6 1.71 FP RELEASE ENASLED 14 10429.2 2.90, SUPPORT PLATE FAILED 2 10457.2 2.90 BURN IN PROGRESS IN LOWER O@T 75 10489.6 2.91 RV FAILED ~ 3 10490.5 2.91 EURN IN PROGRESS IN 1/C UPPER PLENW 141 10493.0 2.91 NO SURN IN LOWER ChPT 75 i

10538.5 2.93 BURN IN PROGRESS IN LOWER CMPT 75 l 10615.0 2.95 ACCUAJLATOR WATER DEPLETED 188 10636.8 2.95 NO SURN IN LOWER ChPT 75 10702.3 2.97 NO BURN IN 1/C UPPER PLENW 141 10709.0 2.97 BURN IN PROGRESS IN 1/C UPPER PLENW 141 10727.5 2.98 UHI ACCOA EMPTY 190 10922.4 3.03 NO SURN IN 1/C UPPER PLENW 141 19284.8 5.36 ICE DEPLETED 132 4.5-4

,. .-..--._...--......__--.m_.,...,, _,. - -.._, - ,.,...,,,,.,,,- ,,- ~ .,_ - - -_ m m m.,-, - -... .---m-

7n-y . (!/:, . . ,. ,'

. .[1 lf, y..

4.6 Sequence No. 6 - AD d

M 3 :-w' . u' a [djij}

4.6.1 Accident Sequence Description AD consists of a large LOCA (10" diameter) initiacor with subsequent failure of the ECCS in the injection mode. The ECCS continues to be

- unavailable in the recirculation mode. Containment safeguards systems are available throughout the accident.

4.6.2 Reactor Coolant System Response Upon initiation of a 0.5454 ft2 cold leg break, the reactor is scrammed, followed by reactor pump coastdown and auxiliary feedwater startup at five seconds. Figures C.6-1 through C.6-5 illustrate the ,

variables of interest. Immediately following break initiation, the primary system pressure rapidly decreases to containment pressure.

The decrease in reactor vessel water level results in core uncovery about 0.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months and initiation of hydrogen production at 0.7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months .

Total hydrogen production from in-vessel Zircaloy oxidation is 840 lbs. at an average rate of 0.25 lbs/sec. This corresponds to an average clad oxidation of 42 percent. The core continues to heat up !

until fuel melting occurs leading to failure of the core support plate at 1.50 hours5.787037e-4 days 0.0139 hours 8.267196e-5 weeks 1.9025e-5 months as evidenced in the vessel pressure increase and level swell in the vessel. The molten corium falls into the lower plenum and fails the reactor vessel at approximately 1.52 hours6.018519e-4 days 0.0144 hours 8.597884e-5 weeks 1.9786e-5 months and the remaining water, hydrogen, and molten corium is discharged into the cavity region.

4.6.3 Containment Response Immediately following break initiation, the lower compartment rapidly pressurizes as the RCS inventory is discharged. This inanediate pressure increase leads to actuation of containment sprays. The IDCOR.4 4.6-1 NEB - Nov. 28, 1984

. 9 T p 1 '. 1 J M ;.3 m 7 A n 4.uRac G i containment spray takes suction from the RWST until 0.39 hours4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months at

" which time successful spray recirculation switchover is achieved. At 1.52 hours6.018519e-4 days 0.0144 hours 8.597884e-5 weeks 1.9786e-5 months , the reactor vessel fails and the containment pressure increases to about 22 lb/in2 The air return fans, containment '

sprays, and remaining ice reduce the containment pressure. Tlie water level in the lower compartment reaches the spillover curb height at i approximately 0.25 hours2.893519e-4 days 0.00694 hours 4.133598e-5 weeks 9.5125e-6 months . Therefore, at the time vessel failure occurs the cavity is flooded. This flooded condition limits core-concrete ablation to the " jet" attack only resulting in about 0.13 ft penetration depth. The flooded cavity results in the inanediate quenching of the corium.

The ice remaining at time of vessel failure is approximately 9.5x105 lbs (about 60 percent melted). At 3.15 hours1.736111e-4 days 0.00417 hours 2.480159e-5 weeks 5.7075e-6 months , all the ice has melted and containment pressurization begins. Following ice depletion, the I containment sprays continue to remove heat from the containment atmosphere. This heat removal rate matches the decay heat at approximately 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months when the containment pressure reaches 21 lb/in2 a Afterward, the containment spray heat removal rate exceeds that of decay heat and the containment pressure decreases, thus precluding containment failure.

IDCOR.4 4.6-2 NEB - Nov. 29, 1984

TABLE 4.6-1 , .r - , n. .

.- . s. v. t'

y' J "a;'Ci L 3

AD U6MAAP .

SEC HR EVENT DESCRIPTION CODE 0.0 0.00 REACTOR SCRAM- 13 0.0 0.00 LETDOWN FLOW OFF 46 0.0 0.00 AUX FEEDWATER ON 154 0.0 0.00 MSIV CLOSED 156 0.0 0.00 PS BREAK FAILED 209 0.0 0.00 HPI FORCED OFF 216 0.0 0.00 LPI FORCED OFF 217 0.0 0.00 MANUAL SCRAM 227 0.0 0.00 CHARGING PUMPS FORCED OFF 232 0.0 0.00 MAKEUP SWITCH OFF 242 0.0 0.00 LETDGWN SWITCH OFF 243 2.1 .00 CONTMT SPRAYS ON 103 60.3 .02 MAIN COOLANT PUMPS OFF 4 60.3 .02 MCP SWITCH OFF OR HI-VIBR TRIP 215 335.5 .09 UHI ACCUM EMPTY 190 791.9 .22 ACCUMULATOR WATER DEPLETED 188 1407.2 .39 REC lRC SYSTEM IN OPERATION 181 1407.2 .39 RECiRC SWITCH: MAN ON 220 1411.0 .39 CH PUMPS INSUFF NPSH 183 l 1411.0 .39 HPI PUMPS INSUFF NPSH 185 l

1743.9 .48 FP RELEASE ENABLED' 14 2664.9 .74 BURN IN PROGRESS IN LOWER CMPT 75 l

2745.0 .76 BURN IN PROGRESS IN 1/C UPPER PLENUM 141 3531.7 . 98' BURN IN PROGRESS IN UPPER CMPT 102 3581.9 .99 BURN IN PROGRESS IN ANNULAR CMPT 122 4796.4 1.33 NO BURN IN LOWER CMPT 75 4916.4 1.37 BURN IN PROGRESS IN LOWER CMPT 75 5315.6 1.48 NO BURN IN. LOWER CMPT 75 5415.5 1.50 SUPPORT PLATE FAILED 2 5424.1 1.51 BURN IN PROGRESS IN LOWER CMPT 75 5473.1 1.52 RV FAILED 3 5479.4 1.52 NO BURN IN LOWER CMPT 75 5484.6 1.52 BURN IN PROGRESS IN LOWER CMPT 75

.. 5503.5 1.53 NO BURN IN LOWER CMPT 75 6782.9 1.88 NO SURN IN UPPER CMPT 102 6828.1 1.90 BURN IN PROGRESS IN UPPER CMPT 102 4.6-3 e

m u 4 6-t 3 0:=a 1 - ~.: ..; 3, ; y AD U6MAAP .

3 @ "2T6MY.

SEC HR EVENT DESCRIPTION CODE 6909.5 1.92 NO BURN IN UPPER CMPT 102 6925.3 1.92 BURN IN PROGRESS IN UPPER CNFT 102 6945.8 1.93 NO BURN IN UPPER CMPT 102 6972.0 1.94 BURN IN PROGRESS IN UPPER CMPT 102 7001.6 1.94 NO BURN IN UPPER CMPT 102 7089.7- 1.97 BURN IN PROGRESS IN UPPER CMPT 102 7132.4 1.98 NO BURN IN UPPER CMPT 102 7228.9 2.01 BURN IN PROGRESS IN UPPER CMPT 102 7274.1 2.02 NO BURN IN UPPEF CMPT 102 7517.9 2.09- BURN IN PROGRESS IN UPPER CMPT 102 7554.5 2.10 NO BURN IN UPPER CMPT 102 7684.3 2.13 BURN IN PROGRESS IN UPPER QuPT 102 7702.6 2.14 NO BURN IN UPPER CMPT 102 7800.6 2.17 BURN IN PROGRESS IN UPPER CMPT 102 7829.8 2.17 NO BURN IN UPPER CMPT 102 7921.2 2.20 NO BURN 'IN ANNULAR CMPT 122 7929.8 2.20 BURN IN PROGRESS IN ANNULAR CMPT 122 8024.9 2.23 BURN IN PROGRESS IN UPPER CMPT 102 8052.9 2.24 NO BURN IN UPPER CMPT 102 8291.6 2.30 BURN IN PROGRESS IN UPPER CNPT 102 8316.4 2.31 NO BURN IN UPPER CMPT 102 8687.3 2.41 BURN IN PROGRESS IN UPPER CMPT 102 8725.5 2 . 42,. NO BURN IN UPPER CMPT 102 8931.8 2.48 BURN IN PROGRESS IN UPPER CMPT 102 8954.0 2.49 NO BURN IN UPPER CMPT 102 9075.7 2.52 BURN IN PROGRESS IN UPPER CMPT 102 -

9118.3 2.53 NO BURN IN UPPER CMPT 102 9184.5 2.55 NO BURN IN ANNULAR CMPT 122 9204.5 2.56 8 URN IN PROGRESS IN ANNULAR CMPT 122 9219.0 2.56 NO BURN IN ANNULAR OuPT 122 9233.5 2.56 8 URN IN PROGRESS IN ANNULAR CMPT 122 9395.8 2.61 BURN IN PROGRESS IN UPPER CMPT 102 9414.2 2.62 NO SURN IN UPPER CMPT 102

'.h. 9740.5 2.71 BURN IN PROGRESS IN UPPER CMPT 102 9759.4 2.71 NO BURN IN UPPER QuPT 102 9827.2 2.73 BURN IN PROGRESS IN UPPER CMPT 102 4.6-4

~

a lhE ' ' .- ,,

!^

r m t 4.6-1 7 3 -- -.. y z -. g AD U6MAAP

" " GONT.

SEC HR EVENT DESCRIPTION CODE 9847.0 2.74 NO BURN IN UPPER CMPT 102 9891.6 2.75 NO BURN IN ANNULAR CMPT 122 9896.5 2.75 BURN IN PROGRESS IN ANNULAR CMPT 122 10084.0 2.80 BURN IN PROGRESS IN UPPER CMPT 102 10106.8 2.81 NO BURN IN UPPER CMPT 102 10167.3 2.82 NO BURN IN ANNULAR CMPT 122

. 10176.1 2.83 BURN IN PROGRESS IN ANNULAR CMPT 122 10274.5 2.85 BURN IN PROGRESS IN UPPER OuPT 102 10294.2 2.86 NO BURN IN UPPER CMPT 102 10339.4 2.87 NO BURN IN ANNULAR CMPT -

122 10359.9 2.88 BURN IN PROGRESS IN ANNULAR CMPT 122 10379.0 2.88 NO BURN IN ANNULAR OuPT 122 10418.1 2.89 BURN IN PROGRESS IN ANNULAR CMPT 122 10527.3 2.92 BURN IN PROGRESS IN UPPER CMPT 102 10552.5 2.93 NO BURN IN UPPER CMPT 102 10685.8 2.97 NO BURN IN ANNULAR CMPT 122 10739.8 2.98 BURN IN PROGRESS IN ANNULAR CMPT 122 10834.3 3.01 NO BURN IN ANNULAR CMPT 122 10857.2 3.02 BURN IN PROGRESS IN ANNULAR CMPT 122 10867.0 3.02 NO BURN IN ANNULAR CMPT 122 10876.9 3.02 BURN IN PROGRESS IN ANNULAR CMPT 122 10941.7 3.04 BURN IN PROGRESS IN UPPER CMPT 102 10975.2 3.05. NO BURN IN UPPER CMPT 102 10994.3 3.05 NO BURN IN ANNULAR CMPT 122 11062.1 3.07 BURN IN PROGRESS IN ANNULAR CMPT 122 11116.6 3.09 NO BURN IN ANNULAR CMPT 122 11132.5 3.09 BURN IN PROGRESS IN ANNULAR CMPT 122 11144.3 3.10 NO BURN IN ANNULAR CMPT 122 11154.7 3.10 BURN IN PROGRESS IN ANNULAR CMPT 122 11314.3 3.14 NO BURN IN ANNULAR CMPT 122 11323.4 3.15 BURN IN PROGRESS IN ANNULAR CMPT 122 11348.7 3.15 ICE DEPLETED 132 11351.4 3.15 BURN IN PROGRESS IN UPPER CMPT 102 11356.0 3.15 NO BURN IN 1/C UPPER PLENLM 141 11386.2 3.16 NO BURN IN UPPER CMPT 102 11422.7 3.17 NO BURN IN ANNULAR OMPT 122 4.6-5

. .. ,-3,, . . . ,

3-.- .

J 1JzJai L Lt d .h,.

. 3 ....tS / t/ t j -lh J 5.0 Plant Response with Recovery Actions A series of parametric studies was performed to determine the effects of the number or amount of emergency core cooling system options available and beneficial as well as possible detrimental operator actions. The following cases were selected for this study:

SD2

- Minimum safegur. ds Full restoration of injection (pre-core melt)

Secondary side (steam generator) blowdown SH2 - Minimum safeguards Partial restoration of recirculation (pre-core melt) l TMLB' - Complete power restoration (pre-core melt) f i Complete power restoration (post-vessel failure)

T23ML - Bleed and feed mode Feed and bleed AD - Minimum safeguards Full restoration of injection (pre-core melt) ;

f IDCOR.5 5.0-1 NE3 - Nov. 20, 1934 i

.' . '4

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. s ., s

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5.1.1 Minimus Safeguards - S 2D # '

The minime safeguards case assumes that only one air return ' fan and one containment spray pump are available during the accident. Since' the ECCS is unavailable during the accident, the primary systies i response is identical for both cases.

t I

The predicted lower compartment pressures for the base case and the minimum safeguards case are compared in Figure 5.1-1. Prior to ice melt, the somewhat higher (less than 1.0 lbf/in a) 2 lower compartment pressure during the accident for the minimum safeguards case is due to the reduced air flow through the ice condenser and the reduced heat removal capability of the single containment spray. The rather rapid inc rease in pressure at approximately 5.2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months (for the minimm safeguards case) is coincident with the depletion of the ice. At approxima.ely 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months the heat removal capability of the single containment eeds the heat production rate of the quenched '

debris b. .er compartment pressure starts to decrease. The maximum ssure reached in the minimm safeguards case is 22.5 lb f/ . -- ely 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , as compared to 21.1 lb f/in2a or both of which are well below the containme.. t. are e of 65 lbf/in 2,,

5.1.2 Full Restoration of Injection - S 2D The purpose of this modified base case is to determine the effect of regaining full ECCS injection capability prior to core support plate failure. Full ECCS injection is defined as regaining all charging pumps, all safety injection pumps, ard all RHR put::ps. Restoration of IDCOR.5 5.1-1 NEB - Nov. 28, 1984

' ~* V > 1, t 't 9 ; %

2

;( n: '. /

J c[..,u

.' 1

.$...,.a.*2..

,i;'i ]a }

injection occurs at 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months . At ths time cf injectite, the reactre vessel water level is approximately 10.0 feet (see Figure 5.1-2),

corresponding to the bottom of the active fuel. The total hydrogen mass produced in the core is plotted in Figure 5.1-3 for the two c ase s. Note that the quenching of the core produces 975 lba of hydrogen (about 325 lbe more hydrogen than produced in the base case).

The greater hydrogen production is due to the ECCS injection water providing additional steam for the Zr, H 2O reaction.

Figures 5.1-4 and 5.1-5 show comparison of the two cases of the primary system corium temperature an3 epper compartment hydrogen mass, re spec tively. The maximum hydrogen mass in the upper compartment for 8 the full restoration of injection case ad for the base case (see Figure 5.1-5) is 225 lbm. The lower compartment pressure for the full restoration of injection case does not exceed 20.8 lbf/in2a, well below the containment failure pressu: of 65 lbf/in2a (see Figure i

5.1-6).

5.1.3 Secondary Side (Steam Generator) Depressurization - s2D The purpose of this case is to determine the ef fectiveness of depressurizing the steam generator to cool and reduce primary system pressure, given a small break scenario with no high pressure injec tion but with low pressure injection (RHR) available.

IDCOR.5 5.1-2 NEB - Nov. 28, 1984

___ _ _ - _ - _ _ _ _ - - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ l

i ,' i

. j 7, ,;.) ;./

- TT?;u:,l ,dJ ;$ C bl31 d (did2.2 Tho plots cf tha primary systs:1 prassura cnd cora watar tegorature for the secondary side blowdown case are shown in Figures 5.1-7 and 5.1-8, respectively, where they are compared to the respective plo ts for the bsse case. Due to the rather ranid decrease .in primary side pressure (i.e. , the primary pressure decreases from 2250 lbf/in2a at 0.0 hours0 days 0 hours 0 weeks 0 months to less than 200 bf/in2 at 0.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months ), it is possible for the RHR pumps to start injecting water into the primary system at 0.4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . Thus, the reactor vessel water level is maintained throughout the accident as shown in Figure 5.1-9. Since the core is never uncovered, there is no hydrogen pEoduction.

i IDCOR.5 5.1-3 NEB - Nov. 28, 1984

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i

.5.2.1 Ministas safeguards - S 2 R The minimm safeguards case assumes that one air return fan, one safe ty injection pump, one charging pump, one RHR pump, and one, containment spray pump are available. For this case, partial, injection is available until the recirculation switchover point is reached, then only the one containment spray is available.

The reactor vessel fails at 3.57 hours6.597222e-4 days 0.0158 hours 9.424603e-5 weeks 2.16885e-5 months for the minimum safeguards case which is 0.26 hour3.009259e-4 days 0.00722 hours 4.298942e-5 weeks 9.893e-6 months after the reactor vessel fails for the base case. This is due to the fact that only one spray spump is operating so the time to recirculation switchover is extended, thus delaying the time to vessel failure due to an increased mass of water available for injection.

The lower compartment pressure for the minimum safeguards case and the base (S2 H) case are plo tted in Figure 5.2-1. Note the similarity in the pressure spike at vessel failure for both cases. Prior to ice melt, the somewhat higher (less than 1 lbf/in2 )a lower compartment pressure for the minimum safeguards case is due to the reduced air flow through the ice condenser ard the reduced heat removal capability of the containment spray. The rapid increase in pressure at approximately 4.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months is nearly conincident with the depletion of the ice at 4.65 hours7.523148e-4 days 0.0181 hours 1.074735e-4 weeks 2.47325e-5 months . At approximately 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , the heat removal capability of the single containment spray exceeds the heat production rate of the quenched debris bed and the lower compartment pressure IDCOR.5 5.2-1 NEB - Nov. 28, 1994

O N ,L:

,d nt Fj.1 " " ' ,.',' J; y /

4 u=2 h :'a*i ud J'x-J aa o*

starts to decrease. The maxianza containment ; pressure reached in the minimum safeguards case is 23.8 lbf/in2 a , which is well below the containment failure pressure of 65 lbf/in2,,

5.2.2 Partial Restoration of Recirculation - S 2H This case assumes minimum injection is available with one charging pump, one safety injection pump, and one RHR pump operating. Once the recirculation switchover point is reached, the ECCS fails as in the base case, and minimum ECCS injection capabilities are not restored until 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months .

The plot of the reactor vessel water level for the partial restoration of recirculation (at 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months ) case is compared to the plot for the base case in Figure 5.2-2. The reactor vessel water level for the mininm2m ECCS injection case decreases at a slightly greater rate (see Figure 5.2-2) due to the reduced ECCS flow rate into the reactor vessel. When injection is restored at 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , the water level in the reactor vessel recovers within 0.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months .

The plots of the total hydrogen generated in core for the partial injection case and base case are shown in' Figure 5.2-3. Note that, as expected, the total hydrogen production for the partial injection case is greater than for the base case (by approximately 300 lbm). The greater hydrogen production is due to increased Zr, H 2O reactions due to the addition of ECCS injection water to the hot, semimolten Core.

IDCOR.5 5.2-2 NES - Nov. 20, 198'.

,,,,g, ,,m,-- . , _ , - ,,- , , - --,,n n , , , , , _,_ ,, ,

1 The plots of the primary system corium temperature for the two cases are shown in Figure 5.2-4. The rapid reduction in corium tesperature for the partial injection case can be seen at 2.6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months due to the quenching of the core.

Figure 5.2-5 shows the upper compartment hydrogen mass of the two c ase s. Note that the maximum amount of hydrogen in the upper compartment is nearly the same for both cases (at approximately 225 lba). The containment pressure never exceeds 20.4 lbf/in2a, which 4 is well below the 65 lbf/in 2 a containment failure pressure.

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FIGUPI 5.2-5 5.2-6 4

i

- e .e

+ -

_ , , , , , - . , _ , . , . . . , . _ , -.- , . . -, ., .. , ,_,c - , -.,.- ,,y,---,----,_y,, . -

/h!,% .3 y

5.3 TMLB' Sequences ,d.,9,

/ f .,

5.3.1 Complete Power Restoration at 2.5 Hours - TMLB' '[* -

.,-- :r 37 This case compares the base case described in section 4.4 with the f assumption of complete power restoration at 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months . The purpose of this modified base case is to determine the overall plant response to restoration of all plant functions before vessel failure. Just prior to power restoration, the pressurizer is empty, and the vessel water level is below the bottom of the active fuel. - At 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , all ECCS pumps, containment sprays, air return fans, igniters, and auxiliary feedwater pumps are restored. Referring to Figures 5.3-1 through 5.3-5 the primary system pressure shows an Ismeediate decrease (at 2.5 r

hours) as feedwater refills the steam generators providing an ef fective heat sink. The primary system pressure reaches a minimum at about 20 minutes af ter power restorstion. At this time, the ECCS pumps quickly refill the primary system, quench the fuel, and drive the pressure up to the shut off head of the charging pumps. The containment response shows a maximum pressure of 21 lb/in2, corresponding to the failure of the quench tank rupture disk due to the pressurizer relief valves relieving the primary system pressure at approximately 1.66 hours7.638889e-4 days 0.0183 hours 1.09127e-4 weeks 2.5113e-5 months . Containment pressure is rapidly suppressed to about 18 lb/in2a af ter power restoration and remains relatively constant. With power restoration at 2.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , the integrity of vessel and containment is never challenged.

IDCOR.5 5.3-1 NEB - Nov. 20, 1984

e .

s \

ijryyp:h!f Ab, a~ ',

,. l 5.3.2 Comp 1*to Power Rester-tion et 5.0 Hours - TML3' "'t '

-This case compares the base case described in section 4.4 with the ,,-

a assumption of complete power restoration at 5.0 hours0 days 0 hours 0 weeks 0 months . The purpose of this modified base case is to determine the overall plant response to restoration of all plant functions af ter reactor vessel failure.

Referring to Figures 5.3-6 through 5.3-11, at 5.0 hours0 days 0 hours 0 weeks 0 months the reactor vessel has already failed and all the invessel hydrogen has been released anc. the hydrogen mass in all the compartments is at a maximum. Th containment experiences a wximum pressure of about 30 lb/in2a at approximately 3.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months due to reactor vessel failure.

The upper compartment gas temperature and hydrogen mass are 1800F and 140 lba, respectively at 5.0 hours0 days 0 hours 0 weeks 0 months . Immediately af ter power restoration, the ECCS system and containment sprays rapidly add water to the containment resulting in flooding the cavity thus providing suf ficient water to keep the corium quenched. Therefore, no concrete attack can occur and the vigorous concrete ablation rate with noncondensible gas generation as seen in the base case is precluded.

When the containment sprays are actuated the temperature and pressure of the lower compartment are quickly suppressed. The containment pressure decreases to about 18.5 lb/in2 a Once the injection phase is complete, successful realignment to recirculation is achieved.

Af ter about 6.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months , containment heat removal continues to decrease

he containment temperature and pressure. Therefore, containment integrity is not challenged.

IDCOR.5 5.3-2 NEB - Nov. 20, 1984

N NM1HMAP .

o R. --

t,

g fi 1 e: :

S.

. I o,

5\ . ,

S: i. *.

g l

'h q

i s: ,

M.

\v J

go:

gN<

o:

6

o. .

3' 3:

00 0.5 to ts to 2.s lo 3.s 4.o 4.s s.o s.s TIME Or) o FIGURE 5.3-1 o:

s a

'. f,', 'I 'w

/ N ,, ,,,, ........ . . . . . . . .........

l: w -

, f'l l

l. v. , .

t 9 g$ - * ? 6 gg. . .

So : *I Es: !

$8:o.

g

$ {.

o L

a: l t

o: I k I

N ,_

o o.o oJ to t$ 2.0 2.S 10 3.S A,o 4.5 5.0 5.5 TIME Ov)

FIGURE 5.3-2 i

5.3-2

4 8 R.

e l

^

t l- :

8R! ll 5a: ;

f s

o: l /.

W. ;

y l g.

s:'.

x 3'

2' 3: . .

0.0 2J 5.0 7J 10.8 ELS 15.8 dJ 2 Eke 2LS 25.0 27J 3dke M 01r)

FIGURE 5.3-3

' 9

.. .I 8

8- i Ei!

1.:

W.

3.: j q

I W <l i E

B' m3 T. .

0.4 2J S.4 7J ' t8.0 ELS M ' fF.S ' 29.8' 22J ' 'M 27J NO M O,4 FIGURE 5.3-4 5.3-3

- _ . , -_y- - . _

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

,,___,_._v.,,. _ _ _ . _ _ _ _ _ ,_ _ _ . __ _ , , _ _ _ ,

FIGURE 5.3-5 o

d n

?. . .

c

// e ' ; ..

t! ,

- O, n.

w .. ;,

.s

\

i N -

y N .N T"

, ci

\

t O-

\ .

.o6 vu

, 3 2 \ i F

+ \ l 9 D

D E

N_ i et e

2 ,

F- i ,

i.

t q 4 ' m l

/ . o, m

JJ q t-n

. o, O

O'S9 0'09 0*SS 0*ds O'St 0*dd O'SC O*OC O'SE 0'dC O'St o'OL (o!sd) S2Ed dWO3 83M01 5.3-4 ee .

. _- -- , w-- -.- w- ,g - - , - - , , .,,-,,,c ,-,,,-r4 --*--,w-- ,

w- r, - ,- -- ,.----w---

EdBU4MAAP N MAP D, 2 .............. ....... ....

I E' .

s _ _ .

g. ,

3, , .

~~.

.5 p

E' (

s.-

k

$ ' ,.o i 2.s s.o 7.s io.o 12.s e.o 17.s no.o 22.s 2s.o 27.s so.o TIME Oir)

FIGURE 5.3-6 4 ;.

! p. /

/

c-

/

[n. 7 . .

@".. /

/

g v- /

g- -

s...

/

o.o 2.s s.o 7.s to.o Q.s tS.o f7.s 2o.o 22.s 2s.o 77.s 3o.o TIME (br)

FIGURE 5.3-7 5.3-6

M '

.. n iM '- .,

8 .

~ ". :. , ,

g- ,

a. v .

I.

9 O'

O' 4 .

9 O

] I 0.0 2.S S.O 7'.S 10.0 Q.S 15.0 ft.S 20.0 22.5 25.0 77.S 30.0 TIME (hr)

FIGURE 5.3-8 f

. 4..

O'

/

. I /

g' E. . f/

8!: 1 _

7 8-

. N -

3 9.

o: g f.,,,...- ....... ....... .....

y _ ,,r o .

l O

'.0 0 2.5 S.0 7.5 10.0 U.S 15.0 fl.S 20.0 22.S 25.0 27.S 30.0 T.VE (br)

FIGURE 5.3-9 5 3-7

e . .

YIGURE 5.3-10 o.

8

/,+,n!.;...

o g

s N o.

s .R

)

CL 4 9 8

1 N I

CN .

e N e D- \ .o6 vi

~to 1

2

\ ,

F s -

\ ,

l o.

0 3 !

(D i o

._] A '. S 2 !

l-- < l

( ,

I

'?

4 _ ', .

l l 3

3 4N

/

O.

O O'S9 0'09 0'55 0'05 0'S t O'Ot O'SC O'OC 0'52 0'0E 0'51 0'0L (0!sd) 53Ed dWOJ B2MO l 5.3-8

s . .,

. ?) ar i.:* ~

p ,

5.4 T, 4 secue cos ' g%y 3;f';,;J [':

e s

, " ,./*.

5.4.1 Bleed and Feed - T23ML b'u' )~.

4 ll This case compares the base case described in section 4.5 with the

' bleed and feed sequence. The purpose of this case is to determine the plant response to an accident sequence in which the recovery actions require bleeding the primary system and using the ECCS pumps' to remove energy via injection water. The assumptions are as follows (1) the PORV mars 2 ally opened at 2500 seconds arut (2) ECCS injection (two charging, two safety injection, two RHR pumps available at 2500 se cond s) . At time zero, the reactor is scramsed and no auxiliary feedwater is available. Referring to Figures 5.4-1 through 5.4-6, the pressurizer water level and pressure initially decrease but quickly stabilize themselves in response to the actuation of the pressurizer h eate rs. The steam generators pressurize to the relief valve set point armi rapidly lose inventory due to the loss of auxiliary feedwater resulting in roughly 85 percent of the inventory being lost by 0.70 hours8.101852e-4 days 0.0194 hours 1.157407e-4 weeks 2.6635e-5 months . At approximately the same time, 0.70 hours8.101852e-4 days 0.0194 hours 1.157407e-4 weeks 2.6635e-5 months , the PORV is opened resulting in a rapid depressurization of the pressurizer (primary system) pressure to approximately 1150 lb/in2 a. At about 0.72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , the ECCS pumps start to refill the primary system.

The injection of cool water inanediately emises primary system pressure and temperature suppression. The ECCS injection arul loss of secondary side cooling drives the pressurizer solid at 0.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months arti the quench tank rupture disk fails at 0.82 hours9.490741e-4 days 0.0228 hours 1.35582e-4 weeks 3.1201e-5 months . The PORV discharges liquid water as the charging ptsups circulate cooling water into the cold leg.

IDCOR.5 5.4-1 NES - July 11, 1984

h.p>,

t]i.O .s Between about 1.5 cnd 3.0 hours0 days 0 hours 0 weeks 0 months , the press: riser (primary syst5m) '

pressure decreases from about 1550 to 1450 lb/in2 a The core (primary system) water temperature decreases from about 5650F at 1.0

%h ?s.Q:)3 gf* ;/l'y hour to about 4000F at 3.0 hours0 days 0 hours 0 weeks 0 months . Beyond 3.0 hours0 days 0 hours 0 weeks 0 months , the primary system pressure slowly decreases due to the equilibration between the pump injection rate and the flow out of the PORV. ' Although the pressure remains somewhat constant, the primary system water teeperature continues to decrease as the ECCS heat exchangers and containment spray continue to remove decay heat from the primary system and the containment. Referring to Figure 5.4-6, the containment maxismin pressure of approximately 18.6 lb/in2a occurs around 6.0 hours0 days 0 hours 0 weeks 0 months due to the depletion of Lee in the ice condenser, but it is suppressed as the decay heat relieved from the primary system is exceeded by the heat removal rate of the ECCS heat exchanger aM containment sprays.

5.4.2 Feed and Bleed -T23MI' This case compares the base case described in section 4.5 with the feed and bleed sequence. The purpose of this case is to determine the plant response to an accident sequence in which the recovery actions require using the ECCS pumps to remove energy via injection water.

The assumptions are as follows: at 3000 seconds, the charging pumps, safety injection, ard RHR pump are turned on forcing water into the primary system. At time zero, the reactur is scrasuned and no auxiliary feedwater is available. Referring to Figures 5.4-7 through 5.4-12, the pressurizer water level and pressure initially decrease L

IDCOR.5 5.4-2 NEB - July 11, 1984

~ .__ - . _ _ _ _ _ _ . , . . - _ _ _ __ _ _ _ . _ . . . . - - ~ , . . _ _ . .__

. . ,g ,

.y 9 ,

bre q:ickly stabilisa themselv00 la response t3 tha act:c, tion, cf tha g ,- . i s.

pressuriser heaters. The steam generators pressuriae to th'e'. relief.

Q. ,, ,, ly valve set point and rapidly lose inventory due to the loss of V .,' 7 .

auxiliary feedwater resulting in steam generator dryout at 0.98 hours0.00113 days 0.0272 hours 1.62037e-4 weeks 3.7289e-5 months .V.i , ?

At approximately 0.83 hours9.606481e-4 days 0.0231 hours 1.372354e-4 weeks 3.15815e-5 months , the ECCF pumps are turned on forcing cool water into the primary system. The injection of cool water inusediately casses primary system pressure and temperature suppression. Soon after initiation of the ECCS injection, the pressurizer is solid at approximately 1.0 hour0 days 0 hours 0 weeks 0 months and the quench tank rupture disk fails at 1.14 hours1.62037e-4 days 0.00389 hours 2.314815e-5 weeks 5.327e-6 months . The PORV discharges liquid water as the charging pugs circulate cooling water into the cold leg. After 1.0 hour0 days 0 hours 0 weeks 0 months the pressuriser safety relief valves are automatically opened to relieve excessive pressure of primary system, the pressuriser is maintained at approximately 2350 lb/in2a. The primary systaa pressure remains constant due to the equilibration between the pump injection rate and the flow out of the PORV.

Although the pressure remains constant, the primary system water temperature continues to decrease.as the ECCS heat exchangers and containment spray continue to remove decay heat from the primary system armi the containment. The containment pressure is maintained at about 17.4 lb/in2a until the ice it depleted at 7.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months and then increases to about 19.5 lb/in2a at 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months . Af ter 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months , the decay heat relieved from the primary system is exceeded by the heat removal rate of the ECCS heat exchangers and containment sprays causing the containment pressure to decrease.

1DCOR.5 5.4-3 NEB - July 11, 1984

T23ML USMAAPAJ16MAAP -

. y-l l.

! krI \. o a -..

l.

w. . . .

,n.

\lil

.s g

M: ; I *

i

y. il;

i 1l a

i .

0.0 0.5 to LS 2.0 2.5 10 3.S A0 AS TIME Oy)

FIGURE 5.4-1 m ......... .......... ......... . . . . . . . . . . .........

y-

t

.: lI

!/

1I N. ;.

e.

m.. .

~. .

N. l h<

3.. A. i

.: . .i

$ \

.. \

W.

.. \

\

.. \ ,

0.0 0.5 to 15 2.0 2.3 10 is A0 AS TIME Or)

FIGURE 5.4-2 5.4-4 L.

m .

TZM. USMAAPAn6MAAP I. .

I: .

8 8: j ~-

3;p

\, . .

l.:'

6 z.: \

v. .

p. .....

m. .

v.

'o o .. o o .. m. m. m

= o.)

FIGURE 5.4-3 1

w

1. :. .

7vvwwnva+

fi i 1 .

l. #:. i -

S::

g 1

1 1g:: :

i\

E '..

g.g: .

I .

1:. .

=.

........- --...... ~........

3:

... u *. ~~u' u m. m. m. a.

M Gr)

FIGURE 5.4-4 5.4-5

(

.. _ ._ __ _ _ i

T23ML USMAAPAJ16MAAP k.

. 3 h:.

.: /

!J Ck. i, ,

e . .

. u.d ,

3 .., ..,

g, -

3 .

w. .,

g.< -

k ,

l ..

k ;' .o 2.o o 4.0 s.o a.o ao no so 14.0 no 20.o TIME Or)

FIGURE 5.4-5 4.

I 3:

l m _

0..e : A

.': \, Qw :

W. -

,; j ', ,.h T

d. , ;

1 Y

. r u N'

o.o 2.0 4.0 8.0 8.0 10.0 no Wo 14.o 10.0 20.o Tk E Ov)

FIGURE 5.4-6

- 5.4-6 4

S#C#

k IMAGE EVALUATION #

4)y e@ + TEST TARGET (MT-3) ////p%

4 4&

'<[d'4,# 4 S+/ %,,+x,9 1.0 'i 83 E lly HE I.I i." E

~

l I.8 l im II.25 1.4 1.6

-

l 4 150mm >

4 6" >

%,,, f 4' 4#f 7hy,,, +

sQ4 4l .~

' ' FU w _______ .

.v , . _ __

_s

o o M @MM i \

y t_ w 7

t ' go '

4 e .?-

}i;g: ..

e-l

< *w h

E:

li il

.. L d' i 88 SJ to ts z.e a.s . u u u TlhE Or)

FIGURE 5.4-7 I.

.: g -. .... .... ......... .......... .........

W. ;;

j h ,

e l

a b et : !

gA. i

.: \ ;

l A, ,

l _

y.:

N.

\ -

II Y.

W6 k

r i -

. . . s . . ., .,

M Or)

FIGURE 5.4-8 5.4-7 w ~,--w--,--.,,----,e,,-,<g --w-e,+ y - ,,o-,,- ey-y -

, ,w,,,, ,-w,,,y v---o ,,-e ,m-

7 NN l

O '?

Ie W, 1

/

3.:

W. ,

.. I d,

g g: \ __....... ........

k. ~

):

i o u o o .. . . 2 TnE Or)

FIGURE 5.4-9 4

i ,: ' ,, -k

{'

f

l

~. ,,

l l f

l f

/

\'

, .t .,

l l

I.

3, l b. '.

! .. '~.'

l i

l -,

N

\s,

'o

~

a.o 2.e' A. ' s.a ' s.o ' te.e na 'ma .o . 2e ThE Or)

FIGURE 5.4-10 1

1 5.4-8

s' 'O T23ML USMAAPM7MAAP i : r.

.: p ,;... p

h. ,~

,; ... u. .s..... . .z.

g. ; ' -. . , ,

, 'e. ' s O '

.' )

9

, c&. -

t .; ...,,

k. '...,

gg.

=O g4 4

O' 0.0 2.0 A0 6.0 8.0 10.0 12.0 WO 16.0 18.0 20.0 TIME Or)

FIGURE 5.4-11 o

4 n<

O.

o:

N.

ao : q MA-v, . . . , - w ,m b- V m ,

O.

.. . C. n\ %I i I

S ,ic .

,jx. ,

l a '

W.

O.

N o.

0.0 2.0 A0 6.0 8.0 10.0 12.0 WO 16.0 10.0 20.0 TME 01r)

FIGUFI 5.4-12 5.4-9

5.5 AD Seque ces

' r" .

5.5.1 Minim e Safeguards - AD U a. '.

s,

' " d .1;; ,c,. ,

The mininum safeguards case assumes that only one air return fan and 0 one containment spray pump are available for operation. Since both ECCS injection and recirculation are inope rable, the primary response is identical for both cases.

The predicted lower. compartment pressure for the minimum safeguards case and the base case are compared in Figure 5.5-1. Prior to ice melt, the somewhat higher (less than 2.5 lbf/in2 )a lower compartment pressure during the accident for the udnimum safeguards case is due to the reduced air flow through the ice condenser and the reduced heat removal c apability of the single containment spray. The rather rapid increase in pressure at approximately 3.0 hours0 days 0 hours 0 weeks 0 months is nearly coincident t with depletion of the ice in the ice condenser at 3.23 hours2.662037e-4 days 0.00639 hours 3.80291e-5 weeks 8.7515e-6 months . At approximately '6.0 hours0 days 0 hours 0 weeks 0 months , the heat removal capability of the single containment spray exceeds the heat production rate of the quenched debris bed and the lower compartment pressure starts to decrease. The maximum containment pressure reached in the udnimum safeguard case is 23.8 lbf/in2a at approximately 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months , which is well below the conta insent failure pressure of 65 lbf/in2a.

5.5.2 Full Restoration of Injection - AD The purpose of this modified base case is to determine the system response to regaining full injection capability prior to core support plate failure. Complete restoration of injection is assumed IDCOR.5 5.5-1 NEB - Nov. 28, 1984

t2 occur ct 1.0 hour0 days 0 hours 0 weeks 0 months which 13 when tha watar levol in tha react 3r vessel is at 10.5 feet (see Figure 5.5-2), which is 'approximately N the

'/

bottom of the active fuel.- ]'dh).M 3, e

When ECCS operation is restored at 1.0 hour0 days 0 hours 0 weeks 0 months , the water level in th2 ( .

reactor vessel is restored to its t.ormal height within 0.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . As was noted in section 5.1.2, the quenching of the core produces more hydrogen than the base case (approximately 900 lba) due to the additional steaming cassed by the ECCS injection water reacting with .

the hot, semimolten fuel.

The primary system corium tengerature and upper compartment hydrogen c mass for the full restoration of injection case are plotted in Figures 5.5-4 and 5.5-5, respectively, where they are compared to the base case plots. Note that the maxinnsa amount of hydrogen in the upper compartment for the full restoration of injection case is 280 lba conpared to 225 lbm of hydrogen base case (see Figure 5.5-5).

The containment pressure never exceeds 22.8 lbf/in2a for this case, thus containment integrity is never challenged, i

IDCOR.5 5.5-2 NEB - Nov. 28, 1984

FIGURE 5.5-1 o

sn l* '

q ,

i 9

(

,N

,o d

/ ~ ,' '* ,O w'% .. .. ,

s

. N g , ,

9 o

2 Ei or ,

e

,h Cf W E

o O Si D ; .'

.e c,- ,

t n n

( ,

.3- <

'. ? .

... A ,o

- c. . .t 7

.c in a.'~ ,

-.... ... ~

T

, *' 1

'nN

.. . , s--- - . : . ::_- _ _ _

w s. .

< g O'tC OT.E 0*EE DE 0'dC O'6L 0'4L O'S ONL Oh 046 7

(D!sd) S3Bd dWOD B3M07 5.5-3 i

b O AD U6MAAPAJ20MAAP R.

o g

N -

m.

-\, f4/ . :.

R, ;g N

\ : ~. s .

pd. . I o.

N. p .

= x. \

l g *e :-

9 N . -'

i

__ _J

\

n g o, :

GS.

O o-vi g -

k e o -

d c.4 o.s o.s to t2 t4 ts o.o d.2 TIME Or)

. FIGURE 5.5-2 y- ,

c. :

o' t u o; e 6 .

.i

l

$~ f I

9*N-.

W /

!E-a .

/

0.2 c.4 c.s o.s to t2 t4 to to 2.0 2.2 o.o TIME Oy)

FIGURE 5.5-3 5.5-4

.. 4 . . . ... . . . .

AD U6MAAPMMAAP i .

r l

(Jit '%

l : . /4 ~ -

n

< j *'"- .a+

~,j 9 j

i. i. *

.. j E< i

o. j l

l d

0.0 OJ to LS .0 15 3.0 15 Ao AS TIME Or)

. FIGURE 5.5-4 k i I

e<

. 4'l N. r

%. . ., ..x -_ -

o-r o- j I f g '

j. '

4 1

.3 0.5 to LS 2.0 15 10 15 Ao AS TIME Or)

FIGURE 5.5-5 5.5-5

4

C,0 Arcident Signaturm

')J-* D ,D

./'.j,4i ,'.., . g

'b; , f;= ' p

y. ,

Accident signatures are presented for each of the base cases Qf' N, ; .[' T;

.. g analyzed . in this report. Thase signatures are generated directly from the MAAP plot files using programs developed at TVA.

Pigures are arranged according to case number as described below.

In all figures, the left axis is used in conjunction with the solid curve whereas the right axis, if present, is used with the dashed curve. An attempt has been made to group unsitiple plots on each plate to show transient interlationships between variables of interest. Cases are identified as described in the report body. .

Case 1 - SD 2 (U1MAAP)

Ca se 2 - SH 2 (U2MAAP)

Ca se 3 -- S2HF (U3MAPP)*

S2HF (U7MAAP)**

Ca se 4 -- 1MLB' (U4MAAP)

Ca s e 5 -- T23ML (USMAAP)

Ca s e 6 -- AD (U6MAAP)

Drains open

- Drains blocked IDCOR.C C.0-1 NEB - July 11, 1984

i .

i:

. .m,

,.- . 5.

m .: ~,

. l!-

Gl!

lg . .,

si . ,. .

. g.! \

E$. N %

r.:

N G!<!

E

g. ~

N . ,

-: s S

b. .

o.o eS 1.0 ts 2.0 2.5 3.0 3.5 Ao AS TIME Oy)

A

/o/. :'

si

/ ,

$..5;

/ .

8l ,

.! / -.sj E.: e. /,: : .E.

[, . -* R

5 l '

5

/ / .

-d Y. *

/ :

s: .

/

k.: / .

o.o o.s to O 2.0 is 2.0 s.s Ao As i TIME Ov)

Figure C.1-1

M UIMAAt'

..:s ..

,W

)-

4 ). , ,

i< .

Q -

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