MIT experts to discuss Japan’s nuclear crisis

Update 3:

Sites to follow:
MIT nuclear science and engineer blog mitnse.com
ansnuclearcafe.org
nei.org
BBC news

The student-host event today (Thur Mar 17, 2011) by the MIT Energy Club was extremely resourceful.  Two figures attached here to explain essentially the basics of the nuclear power structures at Fukushima site.  You can use these 2 figures and point (1) in Update_2 to understand all needed terms that are being tossed around by the news media.  Below are my very beginner-level understanding.  Please check the MIT Nuclear Science and Engineer blog for much more accurate details and terminology.

Figure 1: hand copied from black board

Figure 1:  A schematic of the nuclear vessel at site Fukushima.  Radioactive uranium are stored in small pellets inside zirconium rods called “fuel rods“.  The whole system is submerged  under water.  As
(a) the chain nuclear reaction takes place,
(b) the generated heat boils the liquid and
(c) the steam gathered at the top is piped through channels to
(d) turn the turbine to
(e) generate electricity.  Then
(f) the steam is collected in the cooling channel which is
(g) connected to the ocean (for cooling purpose) before arriving back in the vessel.

In an emergency event such as when the cooling system is disabled,
(h) a set of “control rods” is inserted from below next to the fuel rods to stop the reaction (shut down mode).  At this point,
(i) there is still heat (termed “decay heat“) being generated from the reactions of the by-products of the original nuclear reaction, though at slower rates and capacity that during active reaction phase.  There is a need to remove this heat.  Otherwise,
(j) this heat will continue to boil and
(k) the water level in the vessel begins to drop (see liquid/steam line in vessel in Fig.1). When this water level drops below the fuel rods,
(l) the rods are exposed and heats up at faster rate. If temperature reaches ~1100C to 1200C,
(m) chemical reaction between the zirconium alloy covering the rods and steam produces hydrogen gas.
(n) The steam (and hydrogen gas mixed in) creates very large pressure inside the vessel and is vented out in a controlled manner.
(o) When the vented steam reaches open air and encounter oxygen, an explosion can happen. All this is expected.
(p) Meanwhile back in the vessel, if no water is added, the rod continues to heat up and eventually reaches the rod’s melting temperature ( > 2400 C). I’ll now point you to the scenerio presented at mitnse.com blog for further reading.

So, in summary, all efforts are to keep the level of water above the fuel rods in the vessel.

Figure 2, hand copied from black board

Figure 2. The vessel in Figure.1 is made out of very thick steel. Outside of that is the containment, made out of meters-thick concrete. outside of that is the secondary containment, also made of concrete. The whole thing is then housed in the reactor building. This last layer is only to keep the weather out among other minor purposes, and is not meant to as a layer of protection of radiation.

———————
 

Update2:

I didn’t learn much from the Starr Forum on Mar 16, 2011 (a summary of which is here).  I’m now rearranging this post to highlight what provides me with the most informative background and updates to understand the current situation in Japan:

1. Here’s a very good starting point to understand the construction of a nuclear power structure with various safety barriers to prevent radioactive materials from releasing into the atmosphere in Japan.  The post also explains the meaning of “fuel rod”, “control rod”, and other jargon and inaccurate terms with misleading meaning like “melt”. Use this picture to help you along the way. That site (nuclear energy institute) also has very good info.

2. MIT Department of Nuclear Science and Engineering briefing on Japan Nuclear Crisis, Tues Mar 15, 2011.  Here’s the video of the brief from MIT Tech TV (lots of technical details similar to the blog in point (1) above).

3. MIT “Nuclear science and engineering students, with support from faculty, are also now maintaining a blog at mitnse.com with information about about the incident at the Fukushima nuclear power plants in Japan.”  I’d suggest following this blog closely to get reliable up-to-date information. You can also get the most up-to-date reports from the Japanese Atomic Industrial Forum (JAIF).

There’s another event on Thursday Mar 17, 2011 (in room 56-167, @6-7pm) by the Energy Club at MIT to focus on “Energy Discussions: Hazards and Nuclear Power – Understanding the Situation in Japan“.

———————

i haven’t read much of the news lately because every site i’ve been to has “FEAR”, “PANIC”, and their variations in gigantic letters.  I hope to get some answers at this”Starr Forum: Japan’s Nuclear Crisis” event today.  Will be back later to add more.  The intention to list it ahead of time is just in case anyone around Cambridge / Boston stumbled on my post and can make it, they can get all info here.

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About thả diều
writing-challenged opera-addict

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