Quote:
Originally Posted by transplant99
From what I can gather about the reactors in trouble is that there is little they can do at this point about stopping them from doing so, but more that they need to make sure the containment area is intact to stop radiation from spreading. This has been working to this point but the problem is that when this happens, hydrogen builds up and then explodes much like happened yesterday.
really frightening stuff and the last thing you guys in that part of the world needs to be dealing with.
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The plants are designed to withstand full melt down without any significant radiation release. What they were originally trying was to save the reactors but once they started adding boric acid and sea water that went out the window. I would be pretty surprised if there was any major radiation release. This is not (so far) and should not be anything like Chernobyl. It should be less than three mile island.
I received this from the American Nuclear Society last night (they are experts in the field and despite what many will say are actually up front and honest about things):
Recognizing that information is still not complete due to the destruction of the communication
infrastructure, producing reports that are conflicting, here is our best understanding of the sequence of
events at the Fukushima I‐1 power station.
The plant was immediately shut down (scrammed) when the earthquake first hit. The automatic
power system worked.
All external power to the station was lost when the sea water swept away the power lines.
Diesel generators started to provide backup electrical power to the plant’s backup cooling
system. The backup worked.
The diesel generators ceased functioning after approximately one hour due to tsunami induced
damage, reportedly to their fuel supply.
An Isolation condenser was used to remove the decay heat from the shutdown reactor.
Apparently the plant then experienced a small loss of coolant from the reactor.
Reactor Core Isolation Cooling (RCIC) pumps, which operate on steam from the reactor, were
used to replace reactor core water inventory, however, the battery‐supplied control valves lost
DC power after the prolonged use.
DC power from batteries was consumed after approximately 8 hours.
At that point, the plant experienced a complete blackout (no electric power at all).
Hours passed as primary water inventory was lost and core degradation occurred (through some
combination of zirconium oxidation and clad failure).
Portable diesel generators were delivered to the plant site.
AC power was restored allowing for a different backup pumping system to replace inventory in
reactor pressure vessel (RPV).
Pressure in the containment drywell rose as wetwell became hotter.
The Drywell containment was vented to outside reactor building which surrounds the
containment.
Hydrogen produced from zirconium oxidation was vented from the containment into the reactor
building.
Hydrogen in reactor building exploded causing it to collapse around the containment.
The containment around the reactor and RPV were reported to be intact.
The decision was made to inject seawater into the RPV to continue to the cooling process,
another backup system that was designed into the plant from inception.
Radioactivity releases from operator initiated venting appear to be decreasing.
Can it happen here in the US?
While there are risks associated with operating nuclear plants and other industrial facilities, the
chances of an adverse event similar to what happened in Japan occurring in the US is small.
Since September 11, 2001, additional safeguards and training have been put in place at US
nuclear reactors which allow plant operators to cool the reactor core during an extended power
outage and/or failure of backup generators – “blackout conditions.”
Is a nuclear reactor "meltdown" a catastrophic event?
Not necessarily. Nuclear reactors are built with redundant safety systems. Even if the fuel in the
reactor melts, the reactor's containment systems are designed to prevent the spread of
radioactivity into the environment. Should an event like this occur, containing the radioactive
materials could actually be considered a "success" given the scale of this natural disaster that
had not been considered in the original design. The nuclear power industry will learn from this
event, and redesign our facilities as needed to make them safer in the future.
