ML072640494

Unit 2 Accident - Presentation Slides

ML072640494
Person / Time
Site:	Three Mile Island
Issue date:	03/28/2007
From:	AmerGen Energy Co
To:	NRC/FSME
Widmayer D, ACNW, 301-415-7366
References
WL-130
Download: ML072640494 (16)

Text

TMI-2 Transient - 3/28/79 The Lessons Learned 1

Comparisons

 TMI-1 TMI-2

 Gilbert Associates Burns & Roe

 GE Turbine Westinghouse

 2568 MWt 2772 MWt

 870 Mwe (UP RATE) 880 Mwe

 Runback at that time from full power for turbine trip, not a reactor trip.

 PORV setpoint 2255 vice 2355 psig.

2

Sequence

 Trouble with resin transfer on condensate polisher.

 Pzr being cycled for boron equalization.

Spray valve in manual. Pzr heaters on.

 Condensate Pump 1A tripped.

 FW pumps 1A and 1B trip. (Low suction)

 Main Turbine Trip.

3

8 seconds

 Reactor trip on high RCS pressure

 Pzr heaters returned to automatic control.

 Pressure decreases below 2205 PORV closure setpoint.

 Pzr level peaks at 256 and begins a rapid decrease.

 Letdown flow was stopped 4

13 seconds

 Condenser hotwell low level alarm received

 EFW pump discharge indicated.

 OTSG A water level indicated 74 on startup range.

 PORV and pzr safety valve outlet high temp alrm comes in.

5

30 seconds

 OTSG A water level decreased to 27.3

 OTSG B water level decreased to 28.8

 (41 sec) MUP-1A started (A & B running)

 Pzr low level alarms at 200(setpoint).

 Pzr level reaches a minimum of 158 6

>1 minute

 Pzr safety valve outlet temperature alarmed high.

 Condenser hotwell high water level alarm received.

 Both OTSGs boiled dry

 (00:02:01) ESAS 1600# actuation.

 MU-P-1A ES starts / MUP-1B ES stops 7

> 4 minutes

 RCDT relief valve lifts at 122 psig.

 RCDT high temperature alarm.

 Pressurizer high level alarm received.

 Operator stops MU-P-1C and throttles all high pressure injection valves.

8

> 5 Minutes

 IC-P-1A was started to prepare for max letdown flow.

 Letdown flow off scale high

 Pressurizer level lowers to reached 377.

 Condensate pump 1A was started to try to restore secondary cooling.

 T hot reaches saturation at 1340# and 582F.

9

Chronology

 05:51 Pressurizer level goes off scale high.

 08:18 EFW block valves 12A &B were opened.

 09:23 Letdown flow isolation valve re-opened

 10:15 Pressurizer level back on scale.

 10:48 Rx Building sump high level alarm was received.

10

Chronology

 13:13 DHR pumps are secured (running dead headed).

 14:18 RCDT rupture disc blows.

 20:00 SR-NI departed from normal shutdown profile.

 01:13:29 RCP 2B stopped.

 01:13:42 RCP 1B stopped.

 01:40:37 RCP 2A stopped.

 01:40:45 RCP 1A stopped.

11

Chronology

 02:22:00 The PORV block valve (RC-V2) was closed.

 02:55:00 Site Emergency declared.

12

Estimated Final Condition of Core 13

Lessons Learned TMI-2 Accident Hardware changes

 ESAS status panel

 Thermal Hydraulic Panel

 PT plot

 WR NIs

 RCITs

 Alarm System Reformat

 Additional RMS 14

Lessons Learned TMI-2 Accident Organization Changes - Administrative processes

 Shift Technical Advisor

 Emergency Planning

 Lesson Learned-PRV behavior

 INPO established

 Site Organizational Realignment. GPU established to run nuclear units.

 Radiation protection 15

Lessons Learned TMI-2 Accident Process changes

 Symptom Based Procedures

 Additional Training for Operators

 Simulators BWOG

 SPIP -improve safety system performance

• Control system power supply reliability

• Instrument air system upgrades 16