For comparison from NukeWorker.com
Re: Japan’s Nukes Following Earthquake
« Reply #81 on: Today at 11:39 »
Nuclear Renaissance (poster)
You get to primary containment flooding if you have no other reliable injection source to the vessel. Continued station blackout gets you most of the way there - an explosion in secondary containment does the rest.
Earthquake causes loss of grid
Loss of offsite power causes scram, Main Steam Isolation, and diesel generator start
Tsunami wave trips diesels an hour later station blackout
Steam-driven systems are only means of injection it is necessary to stay at pressure to maintain motive force
No AC means no containment cooling HPCI should not be used due to its very high exhaust steam discharge into containment
Level is held low, in part to minimize injection (and resultant RCIC-exhaust containment heatup) and in part to stay on DC-powered level instruments
Containment venting becomes necessary to avoid overpressurizing containment they probably were considering venting early with uncertainty of quake damage to containment
8 hr battery coping time is exceeded RCIC becomes non-functional in auto
Local manual operation of RCIC becomes necessary (news reports said 4 operators were in the reactor building basement), meanwhile level continues to lower, challenging fuel
Hydrogen buildup in reactor building causes explosion, obliterating secondary containment and possibly damaging injection penetrations (most are AC-powered anyway). News reports said there were on Steam Condensing mode after the MSIV closure, which creates a direct vessel dome path to the RHR heat exchangers.
Enter containment flooding.
As a former Senior Reactor Operator at a large PWR and with BWR experience. Yup. That is what happened (is happening). This scenario is the perfect storm. No Power, No way to get pre-planned Resources on board, No way to change crew perhaps.
I feel horrible for the operators there and wish to all my heart I could help them.
In 2007 I was in a special team assigned to figure out how to cope with scenarios EXACTLY like this. I knew it was going to Containment Flooding yesterday.
After Fukushima Unit 1 blew off the sheet metal building, Did anyone assess the Spent Fuel Pool? The Pool has to have sustained damage. Further, there has to be wreckage IN the Pool, impinging on Spent Fuel Assemblies in their racks. We don’t know if the explosion blew the water out of the pool either. HORRIBLE EVENTS.