Tuesday, March 15, 2011

The Fact : Fukushima Nuclear Explosion

As a future chemical engineer, I feel concerned about Japan Disaster after the earthquake. Hello Malaysian! Feel worried about the radiation? I don’t think so after got this explaination from one of my lecturer during Process Simulation and Modelling class today. The situation surrounding the Fukushima Nuclear Accident, triggered by Japan’s largest recorded earthquake and the resulting 10 m high tsunami, continues to develop rapidly.
The Timeline

a. Reactors 1, 2 and 3 were in operation at Fukushima Daiichi nuclear power plant when the earthquake struck.

b. all three reactors were shut down and control rods were inserted when earthquake struck.

c. Cooling was maintained to remove decay heat

d. decay heat drops rapidly on reactor shut down (e.g a 3GW reactor will reduce to 200MW decay heat after 1s and 50MW after 1 hour… But takes long time (3-6months!) to reduce to negligible levels)

e. sometime (≈1hr) later tsunami struck and mains power was lost to coolant circuit on Unit 1

f. Diesel generators also failed when tsunami hit so cooling was run by backup batteries for 7-8 hours

g. Other emergency diesel generators brought in but insufficient to run pumps

h. loss of coolant leads to fuel rods no longer being cooled by two phase flow (it is a Boiing water Reactor) and eventually get hot enough to recat with steam to produce Hydrogen.

i. Gas pressure in steel reactor pressure vessel rises when coolant systems are not active and is vented to reactor building by engineers. {In my view there is not yet plausible evidence that the temperature of the PV water was sufficiently high to spontaneously split water}

j. The hydrogen in the reactor building is ignited in an explosion which blows out the walls but is not likely to have damaged Steel pressure vessel or concrete containment.

k. Operators are now flooding reactor with borated sea water. Would only do this of they had run out of demineralised water – and were sure that water was not spontaneously being split in the PV.

Feeling free to read the other article? This post is intended to be a concise update of the situation as of 12pm Japan Standard Time, 15 March 2011. For a summary of the situation prior to today, read these posts:

Japanese Nuclear Reactors and The 11 March 2011 Earthquake

Japan Nuclear Situation – 14 March Updates

Fukushima Nuclear Accident – A Simple and Accurate Explanation

TEPCO Reactor by Reactor Status Report 


For you guys who didn’t understand about the explaination [Engineering term], take a deep breathe while reading! Hehehehehehe.


Explosion.note: Wanna design a reactor for urea production for Project Management course! 

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