ML19221A141

Chronology of 790328 Accident from 4 Am to Core Cooling Restored at 8 Pm

ML19221A141
Person / Time
Site:	Crane
Issue date:	03/28/1979
From:	Case E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
NUDOCS 7905190195
Download: ML19221A141 (3)

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/1 CHRONOLOGY OF TMl-2 ACCIDENT UNTil CORE COOLING RESTORED WEDNESDAY MARCH 28, 1979

, FIGURE TIME EVENT I

4:00 & 36 see Loss of Condensate Pump Loss of Feedwater 4:00 + 37 see Turbine Trip 1

Turbine Trip +

Electromatic relief valve opens (2255 3-6 sec psig) to relieve pressure in RCS 1

9-12 see Reactor trip on high pressure (2355 psig) 1 12-15 sec RCS pressure decays to 2205 psig (POV should have closed) 2

+15 sec RCS hot leg temperature peaks at 611.1 F and 610.90F (pressure of 2150 psis, 450 psig over saturation) 2146.9 psig 10

+30 see Event recorder shows 2A and 23 started at same time as turbine trip.

Pressure started up at +30 sec Ic4

+60 see Pressurizer level indication begins to rise 356

+1 min it appears that the Steam Generators A and B are essentially dry 4

2 min & 2 sec ECCS Initiation (HPI) at 1650 psi 9 4

4-12 min Pressurizer level of f scale - one liPI pump (PIC) tripped at

+ 4 min 38 sec.

Second HPI pump (PIA) tripped at + 10 min 24 sec

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12 46 mb RCS flashes as pressure bottoms out at 1350 psi (Hot leg temperature of 584oF) 4

>6 min Pressurizer level indication is off scale high 1Qh

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4 FIGURE TIME

_ EVENT

+7 min 23 sec Reactor building sump pump on 10

+8 min Aux, feedwater flow is initiated by opening closed valves 455 11 min 43 sec (Makeup Pump PI A (ECCS flow HPI) re-started by operators 8 min 18 sec B _S,t ea m C e_ne ra t o r_' p' r es s u r e reached' minimum.'

8 min 21 see A steam generator pressure started to recover after that

+15 min RC Drain Tank diaphragm ruptures at 190 psig due to continued ' discharge thru electromatic relief valve.

11 73 min Operator trips RC pumps in Loop 6

(Pump vibration and reduction and os-cillation in loop flow had been observed).

Il I hr 40 min Operator trips RC p$mps in Loop A (Pump vibration and reduction and os-cillation in loop fl ow had been observed).

14

+1.8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> (est)

CORE BEGINS HEAT UP TRANSIENT - Hot leg temperature begins to rise to 620 F (off scale) and cold leg temperature begins to drop to 150 F (HPl water)

+2.3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> (est)

POV (we believe this is pressurizer power operated relief valve) isolated by operator af ter S.G.-B isolated to prevent leakage 19

+3 hour RCS pressure increases to 2150 psi and electromatic relief valve opened 18 3.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> RC Orain Tank pressure spike of 5 psi RC Drain tank pressure spike of 11 psi 18

+3.8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> (unexplained) - RCS pressure only 1750; Containment pressure increases from I to 3 psi

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FIGURE TIME EVENT 15

+5 hour Peak containment pressure of 4.5 psig containment would be automatically isolated at 4 psig.

We beliave the containment had been manually isolated prior to this time.

19

+5.3 to 6.1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> RCS pressure increased from 1250 psi to 2100 psi 19 7.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Operator opens electromatic relief valve to depressurize RCS to attempt initiation of RHR at 400 psi

. 8-9 hour RCS pressure decreases to 500-450 psi; 19

+

CFT discharge 15

+9.9 hour1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> 28 psi containment pressure spike, sprays initiated and stopped after 5000 gal, of NaOH injected (about 2 minutes of operation) 19

+13.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Electromatic relief valve closed to repressurize RCS, collapse voids and start RC pump 19

+13.5-16 hour RCS pressure increased from 650 psi to 2300 psi 14

+16 hour RC pump in loop A started hot leg temperature decreases to 560 F and cold leg temperature increases to 400 F indicating flow.

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