Text

Forwards Update of Preliminary Annotated Sequence of Events of 790328 Incident
	ML19289G071
Person / Time
Site:	Crane
Issue date:	05/22/1979
From:	Moseley N; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:	Case E; Office of Nuclear Reactor Regulation
References
	NUDOCS 7906260090
	Download: ML19289G071 (40)
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..l May 10, 1979 key. O FRELIMINARY ANNOTATED SECUENCE OF EVENTS MARCH 28, 1979 This report provides additional detail to the April 16, 1979 issue of the sequence of events of the March 28, 1979 accident at Three Mile Island Unit 2.

This report should still be censidered as preliminary since investigatica and data analysis is cegoicg and continues to provida new fnsights into the TMI-2 accident. As such new informatien and/or understanding is developed this report will be updated.

The figures included in this report represent the compilaticn of data frem varicus installed ins trumentaJicn and recording scurces.

Future revisions of this report will identify those sourcec Annotations included aleng with the chrcnoicgy of events, in additica to providing periedic assesseents of the plant SLctus, represent input culled frem intervievi with the operating staff con ucted by the Company.

In cases vbere =anual action was taken by the plant cperating staff the eers the operator" is used in the sequence of events.

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ANNOTATED SECUENCE OF EVENTS

_ LIST OF TICL*RES Firure No.

Title 1

Summary of Reactor Coolant System Parameters Following Turbine Trip (0 to 120 seconds) 2 Sum =ary of Steam Generator Parac_ters Following Turbin~2 T':1p (0 to 120 seconds) 3 Reactor Coolant Syste= Pressure and Pressurizar 'evel (0 to 30 minutes) 4 Reactor Coolant System Pressure and Pressuriter Level (0 to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months )

S Reactor Coolant System Pressure and Saturatica Pressure (0 to 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months ) 6 Reacter Coolant Syste= Lcop A & B Ect and Cold Leg Temperature (0 to 30 ninutes) 7 Reactor Coolant System Loop A & B Hot and Cold Leg Te:perature (0 to S hours)

S Steam Generator A & 3, Level and Pressure (0 to 30 =inutes) 9 Steam Ceneratc; A & 3, Level and Pressure (0 to 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ) 10 Reactor Ccolant System Pressure (C to 120 seconds) 11 Reactor Coolant Syste= Pressure (0 to 120 =inutes) 12 Reactor coolant Syste= Fressure (0 so 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months ) 13 Reactor Coolant System Lcepe A & 3 Flow (0 to 120 seconds) 14 Reactor Coolant System Loeps A & 3 71cv (0 to 20 minutes) 15 Reactor Ccolant System Lecps A & 3 Flov (0 to 120 einutes) 16 Reactor Coolant Syste= Loops A & B 71ov (0 to S hours) 17 Reactor Coolant System Loops A & 3 Flev (0 to 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months ) 18 Reactor Coolant System Lceps A, Hot and Cold Leg Tc=peratures (0 to 120 seconds) 96i jJ 1 /i A rj L"

I 19 Reactor Coolant System Loop A, Rot and Cold Leg Temperatures (0 to 30 minutes) 20 Reactor Ccolant System Loop A, Hot and Ccid Leg Te=peratures (0 to 120 =inutes) i 5

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eas Ocne rat =r A & B Start-Up Level (0 to 120 minutes) hea.= Cecurater A & B Start-Up Level (0 to 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months )

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Title 42 Reactor Ccolant Drain Tank Pressure (0 to 120 minutes) 43 Reactor Coolanc Drain Tank Pressure (O to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months ) 44 Resetor Coolant Drain Tark Pressure (0 to 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months ) 45 Reactor Building Temperature and Pressure 46 Inter =ediate Range and Source Range Monitors (0 to 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months ) 47 Inter =ediate Range and Scurce Pange Monitors (0 to 20 hcurs) 49 Cc=puter Alarm Printer *.ag Ti=e 49 E=ergency Feedwater Pumps Discharge Pressure (0 to 18 minutes) e f

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10 Hay 79 Rev. O PRELIMINARY ANNOTATED SEQUENCE OF EVINTS TMI 2 ACCIDENT OF MARL 28, 19'9 For this chronology a ref erence clock was established with the ti=e of the

urbine trip, 0400:37, defined as the ti=e equal to zero.

The ti=e of each event in the sequence is given as the nu=ber of hours, =inutes and seconds relative to 0400:37, f ollowed in parenthesis by the real time using a 24-hour clock. Tor exa:ple, 1: 52:43 p.n. on March 28 vould be written "9:52:06 (1352:43)."

Oepending upen the accuracy of the source of data for each event, the times appear alene or with the notation "approri= ate."

71.AT: STA CS Three Mile Isistd Unit Two was at 97: power with the Integrated Ccatrol Systec in full autcratic. ?cd groups one thru five were fully withdrawn, rod greups six and seven were 95: withdrawn and rod group eight was 17:

vithdrawn. Resetor Coolant System total flow was approximately 107.5: of design flow and the Reactor Coolant System pressure was 2155 psig. Reactor Ccolant Makeup Pu=p 3 (MU-P-13) was in se rvice supplying nakeup and Reactor Ccolant Pu=p seal inj ection flev. Normal Reactor Coolant System letdevn flev was approximately 70 gp=.

The Reactor Coolant Systen boren ccncentration apprcxi=ately 1030 parts per =1111on.

The Pressurizer Spray valve was (IC-V1) and the pressurizer heaters were in =anual ccatrol whLle spraying the pressurl:er to equalize boren concentrations between the pressurizer and the rec.ainder of the Reactor Coolant Syste=.

The pressuri ar safety valves discharge header ther= occupies were indicating 210 7 to 230 F due tc icakage thru cne cf the Pressuriser Safety Valves (2C-RIA and RC-R13).

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May 10, 1979 Rev. O Steam Generator parameters were ase shown in the folicving table:

Table of Steam Generator Parameters Steae Generater A Steam Cenerator B

1. cop Feedwater 5.7459 ttPPH*

5.7003 MPPH*

Operating Level 56:

57 4 Startup Level 158.8 inches 163 4 inches Steam Pressure 910 psig 889 6 peig Feedwater Terperature 462.7 F 462.7 F 1 ean Te:perature 595 ?

594 F

P?PF. - Millica Peends Per Hour S;ean Generator Feedwater Puaps (FW-P-1A and PW-P-1E) wara in service,

andensate 3cesrar Pucps (C0-P-2A, CO-P-23 and CC-P-2C) were in service, and v ps (CD-P-1A and CO-P-13) were in >ervica.

.h atte=p:. was being Co nd e.s a t e e

=ade to clear a clogged resin transfer line in the standby decinerali er.

A less of feedwater flow transient started when Condensate Pu=p (CO-P-1A) tripped resulting ir both Main eedwater Pu=ps (FW-P-1A and FW-F-13) tripping. The Main Feedwater Pumps trip caused the c.ain turbine to trip.

As was deto: ined later, a c=all brerfs. loss of coolant accident was initiated when the Electrcmatic Relief Valve (RC-R72) did not shut properly af ter cpening to reduce Renctor Coolant Systen pressure.

The high reacter coolant syste= pressure was a direct result of the loss of feed water flew transient which culminated in a reactor trip due to high reactor coolant syste= pressure.

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May 10, 1979 Rev. O Steam Generator parameters were as shown in the f ollowing table:

Table of Steam Generator Paraeeters Steam Generster A Stean Cenerator B Loop Feedwater 5.7459 MPPH*

5 7003 MPPH*

Cverating Level 56:

57.4 Startup Level 158.8 inches 163.4 inches Steam Pressure 910 psig 839.6 peig Feedwater Tenperature 462.7 F 462.7 F Steam Te=perature 595 F 594 F

P.3FH - Million Founds Per Heur Steaa ':enerator Feedwa ter Pumps (FV-F-1A and FW-P-13) vera in service, Condensate Socstar Pu=ps (CO-F-2A, CO-P-23 and Co-P-2C) were in service, and Condensate Pumps (CC-P-1A and CC-P-13) were in service. An atte=pt was beir.;

=ade to clear a cic85ed resin transfer line in the standby decineraliter.

A loss of feedwater flow transient started when Condensate Pu=p (CO-P-1A) tripped resulting in both Main Feedwater Pu=ps (FW-P-1A and FW-F-13) tripping. The Main Feedwater Pucps trip caused the main turbine to trip.

As was dete =ined later, a s=all break loss of coolant accident was initiated when the Electrematic Reltof Valve (RC-RV2) did not shut preperly after opening to reduce Renctor Cociant System pressure.

The high reactor coolant system pressure was a direct result of the less of feed water flov transient which culminated in a reactor trip due to high reactor ecolant systes pressure.

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May 10, 1979 Rev. 0

-00:00:01 Condensate Pump A (CO-P-1 A) tripped.

The trip vas a result of a (C4CO:36) breaker protection relay actuation.

The cause of the relay actuation has not been de te rmined.

-00:00:01 Teadwater Pu=ps (TV-P-IA and TW-P-13) tripped at assenti211y the (C4CO:36) sa=e tL=e resulting in a loss of feedwater flow to both steam generators.

CC:CO:C0 The nain generator and the =ain turbir.e tripped in accordance with (C4CC:37) plant design.

CC:CC:00 All three E=ergency Feedwa ter Punps (IT-P-1. ET-P-2A, ST-P-23) started.

(C'CC:37)

CC:00:03 The Electrocatic Relief Valve (RC-R72) cpaned at the setpoint (04CO:40)

Approximate of CC55 psig.

0C:00:03 The reactor tripped on high Reactor Coolant System pressure at (C400: 45) 2345 psig.

The setpoi=t is 2355 psig.

00:00:08 The operator placed the Pressuri=er Spray Valve (RC-V1) and pres-(04CO:45)

Approxi= ate surizer heaters under automatic control.

00:00:10 The operator announced on Plant ? age Sys tem that TMI Unit 2 (04CO:47)

Approxima te had a turbine trip and a reactor trip.

00:00:13 The operator started Reactor Coolant Makeup Pump A (MU-P-1A),

(C400:50) opened Eigh Pressure Injection Isolation 7alve A (MU-V16A) aad isolated letdcua flow in anticipation of the expected pressurizer level decrease which f ollows the initial increase in level af ter a loss of feedwater ficw incident (Figure 1).

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May 10, 1979 Rev. 0 00:00:13 The Electrcratic Relief Valve (RL-RV2) should have shut at (0400:50)

Apprcximate abcut this tine (closure setpoint of 2205 psig).

The relief valve position indication it the control rece is a red la. p which illuminates when the Electrocatic Relief valve solenoid ir euer- ~

gized. The solenoid on the Electrc=atic Relief Valve (RC-aV )

de9nergized resulting in a deenwrgized (i.e. and implied " closed")

indicatica in the contrcl roca.

Subsequent events showed that the valve had net rc9cated. The plant cperators did cet know at this tiCe that the relief valve had not shut.

ne loss of reactor coolant threugh RC-R70 ras not stopped until the Electrecati:

Relief 51ock Valve (RC-V2) was shut, approxi a tely 2 hcurs and 22 minuter after the start of the transient.

FI.NTI STACS

~he Unit ad just experienced a Turbine / Reactor Trip.

Reactor coolant syste= pressure and pressurizer level vere decreasing rapidly after reaching peaka of 2345 psig and 256 incnes respectively.

U=known to the plant cperators the Electrematic Relief Valve (HC u /2) was not shut and was passing react 7r coolant f rcs the,ceam space at the tcp of the Reacter Coolant Sys to= pressurizer.

Based en centeel rocc: indications, the reactor coolant system pressure and pressurizer icvel uere trending together and decreasing as wa7 expected after a reactor trip.

Th e stca: generators water levels were at about 125 inches and decreac'na at abcut 4 inches /secced.

The stea ynerator stes: pressures were about 1060 psig and decreasing at 32 psi per second.

he turbine bypass valves and a nutber af nain steam relief valves were cpen reliaving stean.

~he Ercrgecy 7ecdvater Pucp? had started but had not reached nor:al discharge precour

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May 10, 1979 Rev. O vater levels had not yet reached the Integrated Control System setpoint of 30 inche.s for the progra=ned cpening of the Emergency Feecuater 7alves (EF-711A and EF-V113) which would admit feedwater to the steam generators.

In addition, the Emergency Feedwater Block Valves (EF-V12A and EF-V123) were shut which also prevented feedwater flew natil they were opened 8 cinutes after the start of the transient.

The reason for the block valves being shut is not inewn. The ecst likely explaination is that the valves were inadvertently left closed after perfor=ance of surveillance testing of the Energency Feedwater Syste= on the cerning of March 25, 1979.

00:00:14 The Emergency Feed pumps (ET-?l, EF-F-2A and EF-P-23) achieved (04CC:51) nor=al discharge pressure (7igure 49).

00:00:14 Staa= generater levels were approxir.ately 120 inches (Figure 34).

(04CO:51)

Apprcxincte Steam pressure had increased to 1065 psig in 3 Steam Generator and 1073 psig in A Stean Generator (Figure 31)

Assuring the steam generatcr safety valves opened at the specified setpoints then 6 of the B Steam Generator safety valves and 8 of the A Staan Cancrator saf ety valves opened.

00:00:15

" Water haccer" was noted in the condensate pump discharge piping (0400:52)

App r oxir.a t e by an auxiliary operator. The piping was displaced several feet according to the auxiliary operator.

00:00:20 The stes: Generator Safety Valves reseated and the Turbine Hypass (0400:57)

Apprcxi= ate Valves OiS7-25a, MSV-25B, MSV-26A and MSV-26B) modulated steam ficv to the =ain condenser to control steam generator pressure at 1010 3 10 poic (Figure 31).

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Rev. 0 00:00:30 Fressurizer Safety Valve (RC-RV13) and Electromatic Relief Valve (0401:07)

(RC-RV2) discharge line tenperature alarms printed out.

The high te=peratures in the discharge lines were a result of tr-high temperature steam flow thru the Electrocatic Relief Valve (RC-RV2) during the reactor pressure transient. The Pressuri:er Safety valve (RC-Rvl3) did not open; the RC-RVIS temperature alarm received was due to the back ficv of steam in the ce==on discharge header shared with the Electrecacic Relief Valve (RC-av2).

CO:00:38 Steam Generator A level reached the Integrated Centrol Syste:

(C401:15)

App cxtrate setpoint of 30 inches at which the Emergency Feedwater Valve (EF-VilA) opens (Figure 34)

Feedvater sas not admitted to Steas Generater A because Emergency Feedwater Block Valve (EF-V12A) was shut.

00:00:39 Reactor Ccciant M3keup Pu=p A (Mt!-P-1A) tripped.

(0401:16) 00:00:40 Steas Canerator B level reached the Intestated Control Syste=

(0401:17)

Appecx1= ate setpcint of 30 inches at which the E=ergency Feedwater valve (E7-Vile) opens (Figure 34).

Feedwater was not admitted to Steam Generator 3 because Zeergency Feedwater Block Valve (E7-V123) was shut.

00:00: 41 The operator started Reactor Coolant Makeup Pump A (MC-P-1A).

(0401:18)

With Reacter Coolant Makaup Pu=pu A and 3 (MU-?-1A and MU-P-13) cperating, the pressurizer icvel rate of decrease slowed (Figure 28).

00:01:00 Pressurizer level started increasing.

Reactor Cociant System

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Apprcxi=ste het leg and cold leg temperatures reached appronizately 575?

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May 10, 1979 Rev. 0 (Figure 6).

The Reactor Coolant Drain Tank pressure was 12 psig and increasing (Figure 41).

00:01:00 The Pressuri:er saf ety Valve (RC-RVIA) high discharge line te=per-(0401:37) ature alar = was received. This alarm was expected and resulted from back flow in the commen discharge header shared with the Electrocatic

'~tR Relief Valve (RC-RV2).

FLW STATUS The Reseter Cooiant Syste= van recovering f rc= the initial icss of feedvater ficw t rans ient. The reactor coclant pressure was still decreasing and pressuri:er level had begun to increase (Ftgures I and 3).

This was not expected as reactor coolant system pressure and pressurizer level should trend together during a 1 css of f eeduster flow transien:. The 7

deviation frc= expected behavior was due to the f ailure of the Electrematic Relief Valve (RC-RV2) to reseat and the reduction in heat re= oval capability of the stea generators beccuse of their low level, which resulted in a lower Reacter Coolant System pressitre and subsequent expansion of the reactor coolant volute. The Reactor Coolant Drain Tank pressure and te=perature started to increase showing the ef fects of the centinued discharge of reactor coolant thru the Electronatic Relief Valva (?C-RV2).

The plant operators did not associate,these indications with leakage past the relief valve but rather with the initial cpening of the relief valve. Steam generator A and 3 levels were 11 innhes and 14 inches, respectively (Figure 34). Ecwever, er.o.rgency f eedva tar was not admitted to the secam generators because the Emergency Fecdwater Block Valves (IF-V12A and EF-V123) were clcsed. The steam generator pressures were being taintained by the Integrated Control System between 973 psig and f

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Nhy 10, 1979 Rev. 0 1020 peig (Figure 31).

Reactor Coolant Makeup Pu=ps (MU-P-IA and MU-P-13) were in operation delivering water to the Reactor Coolant System.

00:01:26 The Reactor Coolant Orain Tank ta=perature normal alar = was (0402:03) received at 85 5 7 which indicated the Reactor Coolant Drain Tank tc ;eratura had returned to the nornal range.

00:01:45 Steam Generators A and 3 boiled dry at this tise.

This'vas (C402:22)

Ap p r o x1:a r.e indicated by a steadily decreasing stea= generator pressure (Figure 8) while reactor coolant system hot leg and :cid leg temperatures were increasing (Figures 19 and 24).

CC:02:C1 Engineered Safeguards Actuation of Righ Pressure injectica (EPI)

(04C2: 33) occurred as Reactor Coolant Syste= pressure reached 1640 psig.

Reactor Coulant Makeup Pump 3 (MU-P-13) tripped auto =atically as a result of the Engineered Safeguards actuation of HPI.

The ES design is such that Makcup Fueps A and C are used for HPI and if running, Makeup Pump 3 is tripped prior to actuation of Makeup Pumps A and C.

CO:00:04 Reactor Coolant Makeup Pu=p C (MU-P-1C) started aute:atically.

(0402:41)

CC:02:12 The Reactor Coclant Drain Tank Relief Valve (VDL-R1) lifted (0403: 49)

Ap proxi=a t e at 120 psig te=porarily halting the Reactor Coolant Drain Tank pressure increase (Figure 41).

The pressure increase was caused by the flow of reactor ecolant frc= the Electrer. tic Ralief Valve (RC-RV2) (Figure 41).

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Itay 10, 19 79 Rev. 0 00:03:14 The operator manually bypassed the nigh Pressurc Injection (0403:51) portion of Engineered Safeguards. Both Reactor Ccolant Makeup Pu=ps A and C (MU-P-1A -and M"-P-lC) were operating.

00:03:26 The Reactor Ccolant Drain Tank high temperature alarm was received (C404:03) at 127F.

00:04: 33 The operator stopped Reactor Coolant Makeup Punp C (EU-P-1C).

(C405:15)

The indicated pressurizer level was 360 inches and increasing rapidly (Figure 29).

C0:04: 33 In an attempt to gain control of the rapidly increasing pressurizer (C405: 15)

Apprcxi= ate level the operater throttled the Eigh Pressure Injection Isolation valves (!"J-V16A and !'U-V163).

PLAliT STATUS The Reactor Ccolant System pressure was 1420 psig and steadily decreasing to the saturation pressure of the Reactor Ccolant System hot leg tempera-ture.

The continued Reactor Coolant System depressurization was due to the failure of the Electre=stic Relief Valve (RC-RV2) to reseat, less of steam generator water level (i.e. reactor heat sink), and reduction in 3? ficv.

Engineering Safeguards, which actuated High Pressure Injection when pressure reached 1640 psig, had been bypassed by the operator to per=it manual contrei of the Make up Pumps and the HPI Isolation Valves.

As the pressuriter level continued to increase, the cperater stopped Reactor Ccolant Makeup Pu p (MU-F-1C) and thrcttled the EP! Isolatica Val res (rm-I SA and MU-V153) in an atteupt to centrol the pressurizer level and not take the pressuri:cr " solid" (Figure 23).

The Reactor Coolant Drain Tank Reltef Valve (WDL-RI) had opened at its i

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May 10, 1979 Rev. O setpoint of 120 psig and was discharging to the Reactor Containment Building Su=p (Tigure 41).

The Reactor Coolant Drain Tank high te=pera-ture alar = had been received as the te=perature of the tank continued to increase. The steam generators had boiled dry as indicated by a con-tinuously decreasing steam pressure while Reactor Ceolant System hot icg and cold leg te=peratures increased (Figures 19, 24 and 32).

This was due to the E=ergeccy Feedwater 31ock valves (ET-V12A and E?-V123) being closed.

00:Ct:52 Operater started Inter =ediate Closed Cooling Pu=p (!C-P-LA) in (0405:29) preparation of putting a seccad Letdown Cooler in service.

00:04: 53 Received the first alarm indicating that Reactor Coolant System (C405:33) letdown flow had been secured. This conflicts with the operator's debriefing statement that letdown flev was isolated at the sa=e ti=e he started Makeup Pump A (MC-P-1A), about 13 seconds into the incident.

00:05:06 Presurizer level stopped its sharp increase at 376 inches and (0405: 43) began to decreacc.

It reached a cinimum of 372 inches and then started to increase at 5 =inutes, 21 seconds into the transient (Figure 29).

Maximum pressurizer level indicarica is 400 inches.

NOTI: Due to the compressed tice scale, this event is difficut to identify on Figure 29 C0:05:15 condensate 3 coster Pu=p 3 (cu-P-23) tripped..

(04C5:15)

C0:05:50 Reactor Coolant Systen pressure stopped its sharp decrease and began (0406:27)

Ap p roxi=a t e to increase. The sininu: value reached was approxir.ately 1350 psig

b (Figure 4).

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May 10, 1973 Rev. 0 00:05:54 Fressurizer level increased beyond the range of the ir.s trument (04C6:31) indication.

00:05:56 The Reactor Coclant System hatics te=perature and pressure reached (0405:33)

Ap p r cxima t e saturation condit1uns of 5817 and 1355 psig as indicated by the reactimeter data and control room vida range re act o r coolant ayste= pressure stripchart respectively (Figure 5).

The Reactoc Ccolant System flew rate decreased sharply, iudicating a reductica da reactor coolant density (Tigure 14).

The increased reactor coolant volu=e resulting free the density decrease contributed to the pressurizer level and pressure behavior at '1:es C0:05:50 and C0:05:54. The reactor out-of-core Source Ranae channel (SI-1) and Intermediate Range Channal (N!-3) nuclear instrumentatica indica-tien did not increase. (Figure 46).

Kad stea= been forced in significant quantities in the reactor core the intermediate range indication shculd have increased significantly.

C0:06:58 Letdown flow of 71.4 gallons per minute uas established in an (0407:35) attengt to reduce pressuri:er level to the normal operating range (200 inches).

00:07:31 Reactor Building Surp Pump A (WD L-P-2A) started on a high reactor (0403:C6) building sump level. The increased sump level was due to the discharge frc= the Reactor Coolant Drain Tank Relief 7alva (WDL-RI) which had been open for appro).icately 4 minutes.

NCTE:

The 2eactor 2uildir6 Oucp Pu=ps generally started about once par shift. For this ressen the pump start was not considered extraordinary by the operator.

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May 10, 1979 Rev. O CJ:08:00 The operator discovered the Energency Feedwater Block Valves (04C3:37)

Approxi= ate (EF-V12A and EF-V123) were shut.

He opened EF-V12A and EF-7123 adnitting e=ergency feedwater to the staas generators.

Indicated steam generator levels were approxi=a tely 10 inches just prior to feedwater additi:n (Figure 35).

00:03:15 The Reactor Coolact Syste: hot leg and cold leg te=peratures began te (04C3:52) decrease as a result of the feedvater added to the stea: generaters (71gure 6).

Stea= Generator pressure increased as the stes:

Eeneraters again beca:e a heat sink for the Keacter Coolant Synta= (Figurc 3).

C0:08:30 The Rasetor Coolant Systc= pressure began to decrease, reflecting (0409:07 the decrease in Reactor Coclant System te=perature (Figures 5 and 6).

00:10:00 The Pressurizar level indicati:n cane on scale.

(0410:37)

?LANT STATUS The reactor cociant pressure ves near the saturation pressure of the reactor ecolant hot leg te perature (Figure 5).

This was the result of the Electrematic Relief Valve (RC-RV2) re=aicing open, high letdcen flow rate, throttled High Pressure Injection Isolation Valves and crergency feedwater addition to the secas generators.

Escrgency feedwater flos was established to both steac generators resulting in increased steam pressures (Figure 3 2).

As heat was recoved f:ca the Reactor Cociant Systc=,

tenperaeure and pressure decreased.

The decreasing temperature resulted in a decrease in reactor ecolant velute.

The pressuri:cr level indication came on scale.

Recctor Coolant System temperature and pressure decreased j

a

=

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12 -

4 May 10. -1979 Rev. O until they stabilized at approximately 550F and 1100 psig respectively (Figures 6 and 11). Reactor Coolant Makeup Pu=p A CMU-P-1A) was eperating.

00:10:19 Reactor Building Su=p Pu=p 3 (UDL-P-23) started. The pu=p start (0410:56) setpoint is 4.416 feet f ree the botto= of the Reacter Contain-

=ent Building Su=p.

The Reacter Building Sucp Punp discharge is believed to have been aligned to the Auxiliary Building Su=p Taak.

00:10:';

Reactor Coolant Makeup Pu=p A (MU-P-1A) tripped.

(0411:01) 00:10:27 The operat=r atte=pted to restart Peacter Coolant Makeup Purp A (0411:C4)

CMU-P-1 A). The pu=p started and then tripped again.

00:10:40 The Reactor 2uilding Su=p high level alar = was received.

Setpcint (0411:25) is 4.650 feet fret the bottoa of the Reactor Centain=ent Building Su=p.

00:11:40 The operator started Reactor Coolant Makeup Pu=p A (MU-P-1A).

(0412:17) 00:14: 50 The Reactor Coolant Drain Tank Rupture Diaphragm (WDl-U26) burst (0415:27) at about 190 psig (Tigure 41).

Design burst pressure is 200 25 psig.

The contents of the Reactor Ccolant Drain Tank were released to the Reactor Ccatain=ent Building at=csphere.

00:24:53 The c;.arator requested the co=puter print the Electro =atie (0425:35)

Relief Valve (RC-RV 2) Outlet tet;erature.

A value of 285.4F vas. indicated.

The cperator attributed the te=perature level to the nor=al cocidewn of the discharge header follcwing the initial L

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May 10, 19 79 Rev. 0 opening and closing of the Electrocatic Relief valva (RC-aV2) and believed the Electromatic Re$1ef Valve (RC-RV2) to be shut.

00:25:00 A high radiatica alarm was received f rem Radiation Monitor (0425:37)

Ap p roxi=a te IC-R-lC92 Inter:adiate Cooling Syste= at the Radiation Monitor Panel. This alarm is nor= ally received following a reac:or trip.

The Inter =ediate Cooling Systen radiation monitor is physically located next to the React:r Building Su=p.

C0:26:03 E=ergency Feedvater Pu=p 23 (IF-P-23) was stopped af ter filling (C436:45) both steam generators to an indicated level of abcut 35 inches (rigure 35).

00:38:10 The operator stopped acacto 3uilding Sc=p Pu=p A (WDL-P-1A) to (C432:47) prevent overflowing the Auxiliary Building Su=p Tank.

00:38:11 The operator stopped Reactor 3uilding Su=p Pu=p 3 (WD L-P-23)

(C428:48)

o prevent everflowing the Auxiliary Building Su=p Tank.

01:10:54 Reactor Building Air Cooling Coils E=eraeccy Discharge Alars (0511:31) was received.

FLA'i' STAG S The reactor coolant was near a saturation temperature-pressure relation-ship at 5427 and 1050 psig. The Reactor Coclant System locp flow rates had decreased from about 69 =illicn pounds pe: bour to approxinately 47 tillien pcunds per hour and continued to decrease (Figure 15).

The Centainment 3uilding te:perature and pressura. had increased frc= 0 psig and 120 F to 2.5 psig and 17CF, as a result of releasing the contents of the Reactor Coolant Orain Tank to :he 2enctor Containment 3uildi.,2 I

a:=csphere (71gure 45).

The Electrecatie 2c11ef Valve (RC-Rv2) was cpen.

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May 10, 1979 Rev. 0..

Reactor Coolant Makeup Pu=p A.(MU-P-1A) was operating. The operator was having difff:ulty controlling the level of Steam Generator 3.

Emergency 7eed Water salves (EF-V' and EF-V123) were shut and the operator was admitting f eed water to Steam Cenerator 3 by cycling Esergency Toed Water Crossconnect Valve (EF-V5B).

01:13:29 Reactor Coolant Puey 23 (RC-P-73) was stepped in accordance with (0514:06)

E=ergency Operating Procedure 2202-1 3 to preclude the possibility of dacage to the Reactor Coolant Pump from operation near reactor coolant saturation temperatura - prassure conditions.

01:13:42 Reactor Coolant Pu=p 13 (RC-P-13) was stopped in accordance (0514:19) with E=ergency Operating Procedure 2202-1 3 to preclude the possibility of da= age to the Reactor Coolant Pu=p from eperation near reactor coolant saturation temperature - pressure conditir.s.

01:20:31 The cperator requested the ce=puter print the Electrecatie (0523:37)

Relief Valve (RC-RV2) outlet te=perature. A value of 233.0F was indica ted.

Based on this temperature the operator continued to believe that the Electromatic Relief Valve (RC-RV2) was shut.

01:26:23 Steam Cenerator 3 was isolated. Main Steam Isolation Valves (0527:00)

(MS-V4B and MS-V73) vers shut.

Escrgency Feedvater Valves (E7-753, EF-VilB and EF-V123) were shut.

The operator suspected a Reactor Coolant System to Steam Generator leak based on the large dif-ference. in steam pressure between the two Steam Generators and the variaticas cf flou and level experienced while controlling 3 Steam Generator. A radionuclide analysis of a sanple from th-B Steam Generator taken at 0724 supported this belief. The sample i

iodina 131 level was 0.491 =ierocuries per milliliter.

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Hay 10, -1979 Rev. 0 01:30:00 The reactor cut-of-core Intermediate Range Channel (NI-3) indication (0530:37)

Approxinate increased from a minimum detectable indication of less than

~I

~11 1 0 x 10 amperes to approximately 1 6 x 10 amperes.

Correspondingly, the cut-cf-core Source Range Channel (NI-1) indication increased from about 1.6 x 10 to approximately 5 3 x 10' ccunts per second.

The indicated increase was not due to reactor core neutren flux level increases but rather an increase in neutron leakage frem the reacter ccre as a result of the f or atica cf steam in the reactor vessel core region.

01:34: 12 Stest Generator A cay have boiled dry (Figure 9).

(053a:49) 01:37:00 The reactor out-of-ccre Intermediate Range Channel (N!-3) indication (05 H:37)

_1, decreased from 2.5 x 10 ' a= peres to a minimum detectable indication of 1.0 x 10-(?igure 46).

The out-of-core a= peres.

Scurce Range Channel (N1-1) indicatic. had a step decrease frem 5 2 x 10 to 1 5 x 10 counts per seconds (Figure 46).

This indicsted an increased ccJerator detrity as a result of the steam collapsing in the reactor vessel.

01:40:00 The operater started raisin Steam Cenerator A level frem 8 (0540:37)

Ap p rcxi=a te inches on the startup range to 50% on the operating range (Figures 35 and 38).

The intent was to establish natural circulation cooling within the Reactor Ccolant System. Reacter Ccolant System Lecps A and 3 cold leg temper: tares both decresced (Tigures 20 and 25).

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May 10, 1979 Rev. 0 01:40:37 Reactor Coolant Pump 1A (RC-P-2A) was stopped in accordance with (0541:14)

E=argency Cpe r ating Procedure 2202 - 1 3 to preclude the possibility of damage to the Reactor Coolant Pu=p from operation at reactor coolant saturation temperature - pressure conditions.

01:40:45 Reactor Coolant Pu=p 1A (RC-P-LA) van stopped in accordance with (0541:22)

E=ergency Operating procedure 2202 - 1.3 to preclude the possibility of da= age to the Reactor Coolant Pump from operatics at re ac to r coolant saturation te=perature - pressure conditiens.

F'_AST STAT"S The Reactor Coolcnt Systes had no forced Reactor Coclant Syste= fiev. All Reactor Coolant Pu=ps (RC-P-1A, RC-P-2A, RC-P-13 and RC-P-23) were stopped (Figure 15). The reactor coolant ave rage te=perature and pressure vere apprcxitarcly 530F and 1000 psig (Figures 11 and 25). Reactor Coolant Makeup Pu=p (M"-P-1 A) was operating.

The operator was attecpting to establish natural circulation ficw to c0cl the reactor core.

Steam Cenerator B was isolated because of : suspected Reactor Ccolant System to Steam Generator 3 leak.

01:54:00 The reactor out-of-ccre Inter:cdiate Racge Channel CNI-3) indication (0534: 37)

_gg Apprcxi= ate increased from less than 1 0 x 10 a: peres to approximately 1.0 10-a= peres (Figure 46).

A corresponding increase was reccrded on the reactor out-of-core Scurce Range Channel (NI-1) indication (Figure 46).

The indicated increase was nct due to inco e neutrcn flux level increases but rather an increase in neutron leakage from the reactor ccre as a result cf the stea= for:ed in the reactor vessel I

core region.

The superheated s tesc spaces f or=ed dae to (1)

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=

m' May 10, 1979 Rev. 0 increased reactor core te=peratures, (2) the absence of reactor coolant systes flev, (3) the decreased Resctor Coolant System pressure which resulted from the Electromatic Relief valve (RC-Rv2) being open and the increased reactor cooland density caused by filling Steam Cenerator A, and (4) the thr~ottled reactor coclant cakeup pump flev.

01:54:00 Reactor Coolant System Locp A hot leg te=pe~ature began to (0534:37)

Approxi= ate increase, reflecting the steam for=ation in the upper reactor core regica (Figure 20),

02:C0:00 Stes= cenerator A level indicatica reached 50% cu the operating (C600:37) range (Figure 39).

02:C0:00 Reactor Coolant System Locp 3 hot leg te=perature began increasing (C6CO:37)

(Figurc 26).

02:10:55 Reactor Coolant System Locp A hot leg en=perature indication increased offscale, greater than 62CT (Figure 21).

02:17:53 The cperator requested the co=puter print the Electro =atic (C618:30)

Relief valve (RC-RV2) cutlet temperature. A value cf 228.7F was indicated.

02:22:00 The Electro =atic Relief 31ock Valve (KC-V2) vas shut, secpping (C622:37)

App roxima te reactor coolant leakage thrcugh the Electrccatic Relief Valve (RC-RV2).

The operator noted that the reactor building pressure started to decrease rapidly (Fiaure 45).

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May 10, 1979 Rev 0 02:27:23 The alarm printer =alfunctioned. The alarm printer function (C62S:00) transferred to the utility printer. The alsrs printer was 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months and 25 =inutes behind in logging data (71gure 48).

02:28:21 Reacter Coolant Loop 3 hotlag ta=perture indication increased (2628:53) offscale, greater than 62C ? (Figure 26).

C2:20:C0 The operator started increasing Stes: Cenerator 3 level fren (C630:37) 20 inches on the Startup Range ro SC:

on the C erating Range.

7 02:40:00 The shift supervisor received the results of eso borca analyses (06:40:00)

Ap p roxi=a t e which indicated the borca cencentration in the Reacter Cec 12nt Syste= was apprcx1=ately 400 pp=.

This. in conjunction with increased neutron levels indicated on the source and internediate range channels, pronpted the shift supervisor to initiate emergency boration of the Reactor Cociant Systes.

NCTZ: The actual boron concentration in the Reacter Coolant Systen was in excess of 1000 ppc.

The sa=ples are believed to have been diluted by distillation in the letdown system.

This however was not kncvn by the plant cperatcrs until several hcurs later.

02: 45:00 Several radiation alarus were received at the Control Roem (0645:37)

Approxi= ate Radiation Monitor ?anel.

02.45:00 The operator s cpped Reactor Coolant Makaup Pu=p C (MU-F-lC).

(C645:37)

App roxina te C2:45:00 The operator cpened Main Stes: 1 solation valves CHS-V43 and MS-V73)

(0645:37)

)

Approxinata to return Staa= Generator 3 to service prior to starting the i

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May 10, 1979 Rev. 0 02:46:23 The operator atte pted to start Reactor Coolant Pu=p 1A (EC-F-1A).

(C646:00)

Approximate The pu=p Vould not start.

02:47:31 The alarm printer function was interrupted which resulted in (C643:CS) the loss of alarm data from 0513:59 to 0648:C3.

02:51:57 The operator atte=pted tc start Reactor Coolant Pu=p 2A (EC-P-21).

(C652:34)

The pump wculd not start.

02:53:19 The operator atte=pted to star Reactor Ccclant ?urp 13 (RC-F-L3).

(C653:53)

The pu=p would not start.

02:54:09 The opa.rator started Reactor Coolant Pu=p 23 (RC-?-:3) and (C654: 46) re-established forced Reactor Ccolant Syste= fiev (71gure 16).

02:54:49 High Pressure Injecticn Engineered Safeguards actuation Icgic (C655:26) reset on increasing Reacter Ccolant System pressure. The set point is 1845 psig.

02:55:00 A Site E=crgency was declared. Notification of of fsite authorities (C655:37)

Approxt ste and organizations was initiated.

02:55:00 The reacter cut-cf-core Inter:ediate Range Channel (N!-3) indica-(C655:37)

-11 Apprext= ate tica decreased sharply frem about 8.0 x 10 a= peres to less than 1.0 x 10~

a: peres (mini =u: detectable level) (71gure 46).

The reactor cut-of-ecre Source Range Channel (NI-1) indicatien shcwed a corresponding decreate which indicated the ec11 apse of the steam spaces in the reactor core regien (Figure 46).

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May 10, 1979 2ev. 0 02:56:19 The operator isclared Staa= Generator B for the second ti=a.

Main (0656:56)

Approxi= ate Stea= Isolation Valves (MS-V43 and MS-V73) were shut.

Energency Feedwater Valves (EF-V53, EF-Vil3, and EF-V123) were shut.

The operator suspected a Reactor Coolant System to Steam Cecerator B leak.

The Condenser Vacuu: Pu=p Exhaust Radiatica Mcnitor (7A-R-748) 5 increased to 5 x 10 counts per =inute.

C3:00:00 Reacecr Cociant Systes pressure increased to 2130 psig (Figure (0700:37)

Approxi=ste 12).

03:03:39 Steam Cenerator pressure control was shif ted f raa the Turbine (0704: 16)

Approxi= ate 3ypass 7alves (MSV-25A and 3 and MSV-26A and B) to the Power Operated E=ergency Main Steam Ou=p Valves (MSV-3 A and 3). The reacter cut-of-ccre Scurte Range Chancel and Intermediate Range channel (N!-1 and NI-3, respectively) indicated an increase cf apprcxi=ately a quarter of a decade (Fisure 46).

03:10:27 Emergency Feedwater Pu=p 2A (EF-P-2A) was stopped. 20th Stems (0711:040 Generators had levels were about 50; in the Cp-rating Ratge (Figure 34).

03:12:28 The operator cpened the Electrc:atic Ralief 31cck Valve (30-V2)

(0713:05)

Approxf ra te in an atte=pt to establish a scr=al operating pressurizer level.

The reactor cut-of-core and Intermediate Range Channel RI-3 indication decreased sharply indicating flow was established thru the reacter core (?igure 46).

03:12:53 T*ce operator stepped aescter Coolant Pucp 23 (RC-P-23) after he (0712:53) cbserved no ficw indication and a pu=p running current of less i

than 100 a= peres.

Nor=al reactor coolant pump cperating currect j

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May 10, 1979 Rev. O

~

is approxi=ately 600 a=peras.

A close exastmation of the flew recorder trace indicated a slight a=ount cf reacror coolant flow.

~

03:18:13 The reactor cut-of-core Intermediate Range Channel (NI 1) indica-(0713:00)

-11 Approximate tica increased from less chan 1 0 x 10 a= peres to ahone

'.7 x

-10 a= peres, which again indicated ste&= vas formed in 10 the reactor core (Figure 46).

03:19:45 Engineered Saf eguards actuation occurred as a result of icv Reacter (0720:22)

Coolant Syste= pressure (Figure 4).

The setpoint is 1640 psig.

02:20:12 Reactor Coclant Makeup Pu=p C (MU-P-IC) started auto =stically.

(0720: 41)

Reactor Coolant Makeup Pu=ps A and C (MC-P-1A and MU-P-!C) were cperating.

NCTI:

Ouring an Engineered Safeguards actuation, High Pressure Injection utilizes Reactor Coolant Makeup Purps A and C (MU-P-1A acd MIT-P-IC).

03:21:00 The reactor out-of-core Scurce Range Channel (5I-1) and reactor excore (0721:37)

Approxicate Inter:ediate Range channel (NI-3) indication decreased rapidly indicating ficv ves established thru the reactor cara (Figure 46).

FLANT STATUS The Reactor Coolant System was at minimum forced flow condition with all Reactor Ccolant Punps (RC-P-1 A, RC-P-2A, RC-P-13, and RC-P-23) stepped.

Alter at c= pts to establish natural circulation failed, the cperator started Reactor Cociant Pu=p 23 (RC-P-23).

Eavever, based en a no flov indication and a pu=p running currant of less than 100 anps Reactor Coolant Pun; 22 vcc cte, ped cfter 19 =inutes.

Superheated stas =/ gas was present in the reactor vessel head and Reactor Cool. ant System hot leg.

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May 10, 1979 Rev. 0 -

Both Reactor Coolant Systen hot lag temperatures were off scale high (i.e.

grecaer than 52CT). The Reactor Coolant System cold leg te=peratures were 4557 for Lcep A and 390F for Loop B.

Steam Generator B was isolated due to a suspected Reacede Coolant System to steam generator leak.

Steae Generator A pressure control was by means of the Power Operated E=ergency Main Steam Du=p Valve A (MSV-3A). An atteept was in progress te control Reactor Coolant System Pressurirer pressure and level with the Electrcnatic Relief Block valve CRC-V2).

This resulted in lower Reactor Coolant system pressure which caused an Engineered Safeguard actuaticn on low Reactor Coolant System pressure. Consequently, both reactor coolant Makeup Pu=ps A and C (MU-?-1 A and 1C) were cperating.

03:23:23 A Ceneral E=ergency was declared as a result of a radiation reading (0724:00)

Apprcxicate of 8 R/hr in the Containeent Building. Notification of offsite authorities and organizations was initiated.

03:30:00 The operator shut the Electrotatic Relief Block valve (RC-V2).

(0730:37)

Apprcxicata The pressurizer level was 220 inches and the Reactor Coolant System pressure was 1420 pcis (Figures 4 and 12),

03:35:08 The operator started E ergency Teedwater Tue.p 2A (E?-P-1A).

Steas (0733:43)

Generator A 1cvel had been cantinucusly falling fres 68: to 44%

of Operatirg Range during the previcus 45 minutes (71gure 39).

03:37:00 The operator s:cpped Reactor Coolant Makeup Pung C (MU-P-lC)

(0737:37) because pressurizer level was rapidly increasing. Pressuri:er level indication was 350 inches (71gure 4).

03:51:00 The operator opened the Electrc=stic Relief Block valve (RC-72)

(0731:37)

Apprcximate in an atte=pt to decrease pressurizer level, which had increased

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i to 395 inches (Figure 4).

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May 10, 1979 Rev. 0 03:53:40 Inter =ediate Cooling Pump (IC-F-B) tripped.

(0756:15) 03:55:39 E=gineered Saf eguards actuated en Reactor Building hiah pressure (0736:16)

(Figure 45).

The nominal setpoint is 4 psig; the tripped occured at3.58 psig.

03:55:39 The Reactor Building isolated autocatically as pa r t of Ecgiacered (0756:15)

Safegua&dr actuatics frc= Reactor Zuilding high pressure. Isola-tien occurred at the nc=inal setpcint cf 4 psig.

03:56:04 Raactor Cociant Makeup Pump C (MU-?-lC) was started autcaatically (C75o:41) by the Engineered Safeguard actuation.

03:59:23 Reactor Building Emergency Cooler B was shutdown.

(CSCO:00) 03:59:53 Resetor Building Emergency Cooler 3 was started autenatically (0800:30) by the Engineered Safeguards actuation.

04:08:37 The operater started Reactor Coolant Pucp 1A (RC-P-1A) to (C809:14) re-establish Reactor Coolant Flcw.

SC E:

During the previcus run of Reactor Ccolant Pump 23 (RC-P-23) due to the indicatica observed,it was thcught tha t the punp eight cc:

have started.

Fer this reascn it was decided to watch the starting current for another pu=p start. Ecactor Coolant Pucp LA (RC-F-LA) was started and a correct starting current was observed by the operator.

As before, the indicated pucp current slcwly decreased to less than 100 arpercs.

04:09:14 The operater stopped Reactor Ccolant Pu=p IA (RC-P-1A) after (C509:51) observing a no-flow indication and a running current less than 100 5*

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May 10, 1979 Rev. O C4:17:17 Reactor Coolant Makeup Pump A (MU-F-1A) tripped.

(0817:54) 04:17:22 Reactor Coolant Makeup Pu=p C CKU-?-lC) tripped. Ito leactcr (0817:59)

Coolant Makeup Pu=ps vere operating.

04:13:17 The operator atte=pted to start Reactor Coolant Makeup (0313:54)

Pucp A (MU-P-1A). The pucp would not start.

04: 21:53 The cperator started Reactor Ccolant Makeup Pu p 3 (MC-P-13).

(C322:30)

Apprexi= ate C4:26:59 The cperator started Reactor Coolant Makeup Pu=p C (MU-F-IC) ;

(0S27:36)

Appecxicate it tripped, and was restarted.

C4: 30:45 The operator stopped Condenser ?acuu

?u=ps lA and IC (VA,P-1A (0531:22) and VA-P-lC) and brcke =ain condenser vacuu= af ter experiencing difficulty with the operation of the auxiliary boiler.

04: 3C:45 The operator epened the Power Cperated Emergency Main Stea=

(C331:22)

Approxt:2e tu=p Valve (MS-V3A) to induce natural circulatien in Stes= Generator A.

Stea= Generater 3 was still isolated.

05:17:38 The alar = printer was returned to service and the alar = functien (C918:05) was transferred f rom the utility printer to the alar = printer.

05:13:00 The operator closed the ~1ectrocatic Rolief 31cck 7alve (RC-V2)

(C913:37) in an attempt to co= press the raactor coolant and collapse the superheated stea=/ ss.

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May 10, -1979 Rev. O C4:17:17 Reactor Coolant Makeup Pump A (MU-F-1A) tripped.

(C317:54) 04:17:22 Reactor Coolant Makeup Pu=p C (MU-P-1C) tripped. No Reactor (0817:59)

Coolant Makeup Pumps vere operating.

04:18:17 The cperator attempted to start Ecactor Coolant Makeup (C318:54)

Pump A CMU-P-1A). The pump would not start.

04: 21:53 The operator c:arted Reactor Coolant Makeup Pu=p 3 (MU-P-1B).

(C322:20)

Apprcri= ate C4: 26:59 The cperator started Reae:cr Coolant Makeup Pu=p C (MU-P-IC) ;

(C327:36)

Apprcx1= ate it tripped, and was restarted.

04: 30:45 The operator stopped Condenser vacuum Pumps IA and 1C (VAsP-1A (0831:22) and VA-P-lC) and broke =ain condeaser vacuu: a'ter experiencing difficulty vi:h the operation of the auxiliary boiler.

04:30:45 The operatar epened the Pcwor Operated Emergency Main Steam (C331:22)

Apprcxi=ste Dump Valvu (MS-V3A) to induce natural circula:1cn in Steam Ce:crator A.

Steam Generater 3 was still isolated.

05:17:38 The alarm printer was returned to service and the alar = functico (0913:05) was transferred from the utility printer to the alarm printer.

Of LS:C0 The operator closed the Electrecatic Ralief 31cck 7alva (RC-V2)

(Gyl3:37) in an atte pt t a ccepress the reactor ecolant and collapse the superheated stec:/ gas.

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.s.s Rav. O FLANT STATUS All reactor coolant pu=p s (RC-P-1A, RC-P-1A, RC-P-1B and RC-P-23) were stepped. A superheated steam / gas space was present in the upper vessel and ho: leg regions. Attempts to re-es tablish reactor coolant *1ev using Raac:or Coolant Pump LA (RC-P-1A) had not been successful. The reactor coolant hot leg te=perature continued to read of f-scale (i.e. greater

han 62CF). The reactor cociant cold leg te=peratures were 180 F f o r Loop A and 225F for Loep 3, and both were decreasing (Figures 21 and 26). Steam Generator A level was at 48% of the operating range (Figure 39).

Steam Generater 3 was isolated, with a level at 66 of the operating range

(?igure 39).

Condenser vaeuem was lest due to the auxiliary stea= bciler tripping and loss of adequate =ain steam pressure.

Steas Generator A was stearing through the Fever Operated Energency Main Steam Ducp Valve (MS-V3A).

Atte= pts to ebtain a nor=al operating pressurizer level of 220 inches of wa:er and establish pressure control using the pressuri:er were not successful.

The Electrenatic Relief Block Valve (RC-V2) was cycled to assia: in this edfert, resulting in increased reactor building pressure. The first Engineered Saf eguard actuatica on hiah reacter building pressure was received and, four minutes later, bypassed by the operator tc re-establish c oling vater to various plant equipment within the reactor building. The reactor building pressure continued :o stay abcVe the isolatica trip se: point for approxi=ately 2 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months (Figure 4f).

The Station Manager cade the decision to =sintain centfnucus High Pressure Injection and increase Reactor Coolant System pressure in an a t t e=p t to collapse the superheated stean/ gas space in the Reactor Ccolant Systen.

This firs t attempt lasted f or approxi=4:ely 2 hcurs.

05:20:00 2eacter Coolant System pressure started to ine: case frca 1250 psig.

(C920:37)

Approx 1: ate

.he increasing trend in Reacecr Coolant Systes pressure continued L

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May 10, I'979 Rev. O for approximately 45 minutet until pressure stabilized at about 2050 psig (Figure 12).

05:54:00 The cperator coamenced fillin: Stes= Cenerator A to 95% of the (0954:37)

Approxi= ate operating range to induce natural circulatioc. A Staam Genera-tor indicated level reached 100 at 07:30:00 (1130:37)

(?igure 39).

07:30:C0 The Station Manager directed the operator to open the Electre=atic (1130:37)

Approriza te Relief Eleck Valve (RC-72) and the Pressuri:Sr Spray Valve (RC-71) to rapidly depressuri e the Reacter Coolant Syste= acd actuate the Core Ficod Syste while High ?ressure Injectica was caintained (Figure 12).

This was done af ter the operator observed no evidence cf natural circulation while the Reactor Coolant Systc= pressure was above 2000 psig.

The reduction in Ecactor Ceciant System pressure was also donc to approach conditions which vculd allow the Decay Heat Re=cval Pumps ?lA and 13 (OH-?-1A and DE-F-13) to be put into service.

08:11:26 The Core Flood Tank A high level alarm was received. The levei was (1212:03) 13 32 feet.

C3:30:00 The ?caer Cperated E=crgency Main Stcan Da=p Valve (MS-53A) was (1230:37) shut at the request of corporate =anage=ent in response to ecacern expressed by the state governcent.

08:31:06 The operator started Oecay Heat Re=cval Pumps 1A and 13 (IE-?-1A (1231:43) and DE-?-13) in preparatica for placing the Decay Eeat System in service.

E i

The level E

C8:54: 56 Core Flced Tank A normal level alarm was received.

5

,t n- ' "y was 13 13 feet.

May 10, 1979 Rev. 0 09:04:18 The operator stopped Reactor Coolant Makeup Pu=p C (MU-P-1C).

(1304:55) 09:49:43 A hydrogen detonation occurred La the Reactor Building. Hydrogen (1350:20) gas frem the reactor coolant collected in the pressurizer and was vented through the Electrematic Relief Valve (RC-R"2) to the Reactor Coolant Orain Tank and then released to the Reactor Building through the Drain Tank Rupture Diaphrage (WOL-C25) which had been breached.

The hydrogen conces: ration even:ually reached an explosive sixture and detonated.

C9: 49:44 Engineered Safeguards actuatics cceurred on high-high reactor (1350:21) building pressure (?igure 45).

The ac tpoi.n t is 28 psig.

This is the result cf a 23 psig building pressure impulse free the hydregen detonation. Reacter Building Isolation and Contain=ent Spray were actuated.

Reactor Ccolant Makeup Pu=p C (MU-P-IC) and Reacter Building Spray Pu=ps A and 3 (35-P-1A and BS-P-13) started autem

=atically.

09:49:50 Reae:or Building Spray 7alves (3S-VIA and ES-V13) cpened.

(1350:27) 09:49:58 Reactor Cociant Pucps lA and 13 (RC-P-LA and RC-P-13) inlet air (1350:35) temperature high alar =s annunciated and Prescurizer Safety Valves (RC-RIA and RC-R13) discharge line ta=perature high alar =s odnunciated.

09:50:24 The cperator stopped Reactor Coolant Makeup Punp C (MU-P-1C).

(1351:01)

C9:55:30 The cperator stopped Reactor 3uilding Spray Pucps A and 3 (3S-P-1A (135e:07) and 3S-P-1B).

BC-P-1A and.'.S-P-13 were ope ra:ed f or ap proxicately i

t 5 minutes and 40 seconds.

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Rev. 0 05:56:53 The cperator stopped Decay Heat Pucpn A and 3 (DH-P-1 A and_ DH-P-13).

(1357:35)

These pu=ps were run in anticipation of using the Decay Heat System. The Reactor Coolant System pressure was never low enough to use the Decay Heat System.

10:26:18 Reactor Coolant System Loop A hot leg te=perature decreased to (1426:55) within the instru=entation range (Figure 22).

This was the result of the stea=/ gas space in Loop A hot leg collapsing.

10:31:25 The operator started Reactor Cociant Makeup Pu=p C (MU-?-IC).

(1432:02)

Reactor coolant pressure was approri=ately 440 psig.

10:34:2?

The Reattor Coolant Syste: Locp A hot leg te=perature increased (1435:06) beycad the range ci the instru=entation. When High Pressure Injection was directed to Lcep 3 hot leg the steam / gas ipace in Locp A hot leg re-established itself (Figures 22 and 27).

10:35:55 The operator stopped Reactor Coolant Makeup Pucp C (MU-F-lC).

(1435:32) 10:39:29 Reactor Coolant Syste: Loep A hot leg teeperature decreased (1440:06) to within the instrumentstion range.

This was the res ult of the steam in Loop A hot led again collapsing when High Pressure Injection to Loop A hot leg was re-established. The Lcep A hot leg steam did not return.

11:06:00 Pressurizer level started decreasing frec 370 inches to 180 inches (1406:37)

Approxicate over a period of 18 =inutes (Figure 30).

11:12:C0 Reactor Ccolant System Locp A cold leg te perature started to (1512:37)

Apprcxi= ate increase from 200F to 400F indicating the occurrence of natural cirtulation in Locp A (Figure 22).

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May 10i"1979 Rev. 0 11:18:34 The operator started Reactor Coolant Makeup Pu=p C (MU-F-lC)

(1519:11) to stop the rapid f all in the pressurizer level.

11:24:00 Pressurizar level stopped decreasing at 180 inches and started (1524:37) increasing, going off scale during the next hour (?igure 30).

11:28:12 The operater accpped Re. tor Ccolant Makeup Pu=p C (MC-P-1C).

(1523: 49) 11:32:37 The operator started Reactor Coolant Makeup Pump C (MU-P-1C)

(1533:14) to raise the pressurizer level.

11:35: 48 The cperator s: caped Reactor Coolant Makeup Pu:p C (MU-P-lC).

(1536:25) 11:36:C0 The operater cc= enced filling Stea= Cenerator 3 to 97% en the (1536:37)

A pr0xt: ate Cperating Range to induce additional ecoling of the Reactor Coolant System. This level was reached at 12:00:00 (16C0:37)

(Figure 39).

12:48:00 Pressurizer level indication ca=e on scale (Figure 30).

(1648:00)

Ap p roxi= ate 13:02:23 The operator started Condecser Vacut= Pu=p IC (VA-P-LC) in an (1703:00) attempt to re-establish vacuum. The auxiliary boiler had been returned to service and was supplying gland sealing stea to the main turbine.

13:13:10 The operator started Ccedenser Vacuus Pucp 1A (VA-P-1A).

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PLA.VI S3 TU3 All reactor coola nt pu=ps (RC-P-1 A, RC 't-2A, RC-P-13 and RC-P-23) vara secyped. Superhented steam / gas existed in the vessel head and Loop 3 hot len.

The icop A hot leg stea=/ gas was collapsed and natural circula-tion flow established in this loop.

Condenser vacuum was re-e s tablished af ter the auxiliary steam boiler was returned to service. Steas Cecerator A var stea=ing to the condenser and Stes: Generator 3 was isolated.

Th e Elect:ccatic Relief Block Valve (RC-V2) was open, keeping the Reactor Coolant Sys te= depressurized to 650 psig (Figure 12).

Vesting through the Electrecatic Relief Valve (RC-R2) to the reactor building resulted in a hyd: gen eeneentratien increase and subsequent denotation which caused a 28 psig Reactor 2uilding pressure pulse.

Atte= pts to use the Cor a Flood System to cool the cere over the last six ; urs had resulted in 11=1ted success. The reac:or core was being cooled by (1) Seca: Cenerator A stes:ing, (2) High Pressure Injection flew into the Reactor Coolant Systen and then to the Reacto: Sc.ilding floor via ihe Electrc=atic Relief Valve (RC-R2) and (3) Core Flced Tank A partial discharge.

13:15:00 The operator closed the Electo=atic Relief 31cck valve (RC-72)

(1715:37)

Approxf= ate in an attenpt to collapse the remainir.g stea=/ gas voids by going to a high Reacect Coolant System pressure (Figure 12).

13:23:04 The cperator started Reactor Coolant Makeup Panp C (MU-P-?.C) to (1723:41) assist in increacing Reactor Coolant System pressure.

14:43:15 Th' cperator stopped Reactor Ceolant Makeup Fu=p C (MU-F-1C)

(1843:52) to slow the rnpid increase in reacter coolans prescure.

14:34:00 Rese cr Coolant Syste= pressure reached 2330 psig (Figure 12).

(1234:37)

Appecxi=ste

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Hay 10, 1979 Rev. 0 '

15:32:42 The operator started Resetor Coolant Pump 1A (RC-P-1A) and after (1933:19) approx 1=ately 10 seconds stopped the pump.

This was done to verify the pu=p starting current was correct. Reactor Coolant System pressure d:cpped from 2340 peig to 1440 psig and Loop A cold leg temperature decreased from 400F en 2909 (ri a'ir *

17 and 77).

15: 49:08 Reacter Coolant System Leop 3 hot leg temperature decreased to (1949:45) within the indication range of 572.6 F (Figure 2 7).

15:50:09

~he operator started Reactor Coolant Pu=p 1A (RC-P-1A), Raactor (1950: 46) coolant pressure drepped frem 2250 psig to 1380 psig ar.d eventually stabilized et ICCO psig.

De average reacter cociant te=perar.ure drcpped to 290 F and eventually stabilized at 250 F (Figure 22).

PLA::~ "TA~~'S 22 15:20 Reactor Ccolant Syste= and Stea= Generator conditiets were:

(C215:37)

Apprcxi=ata Reactor Coolant System pressure was 1165 psig.

Pressurizer Te=perature was 5517 (pressurizer heaters =aintainicg te=perature).

Pressuri:er level indicatice was 297 inches.

Steam Generator A was stea=ing to the Main Condenser.

Stea= Generator 3 was isolated.

Reactor Coolant Makeup Pu=p 3 (!"J-P-13) was cperating to supply Peact(

Ocolant Pu=p seal injection flow.

Reacter Cuciant System Loop A cold leg te=perature was 256 4F.

Reactor Coolant Syste L:cp 3 cold leg tecperat tre was 252.47.

P.cactor Ccolant Systa.m Lecp A hot leg te=perature was off scale

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less than $20 0F.

Reactor Coolant System Lcep 3 hot leg te=perature = of f scale lov, g

1.e.,

less than 320.0c.

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