World Is Ignoring Most Important Lesson From Fukushima

mdsolar writes "Kenichi Ohmae, an MIT-trained nuclear engineer also widely regarded as Japan's top management guru, is dean of Business Breakthrough University. In the CSM he writes: 'Fukushima's most important lesson is this: Probability theory (that disaster is unlikely) failed us. If you have made assumptions, you are not prepared. Nuclear power plants should have multiple, reliable ways to cool reactors. Any nuclear plant that doesn't heed this lesson is inviting disaster.'"

Comments

Or use a different type of reactor....

[blunttrauma]

Or use a different type of reactor that doesn't rely on electricity for cooling. See any of Kirk Sorensen's liquid-fluoride thorium reactor talks on YouTube. His talk at Ted is a good 10,000 overview and only 10 minutes long: http://www.youtube.com/watch?v=N2vzotsvvkw

Re:Correct

[Troggie87]

For those who don't follow reactor tech and don't know whats being talked about, liquid sodium reactors use literally a vat of salts and radioactive material in a magma-like sludge. There is a plug at the bottom of the vat with a melting point that is well above operating spec, but well within reach if the reactor lost cooling. If all other failsafes are disabled, the plug melts and all the molten sludge runs into 2-3 smaller tanks. The reaction then stops being self sustaining, and you just have to recover the containment units and repair the reactor. Its literally idiot proof barring a fault line opening a chasm beneath the plant or a direct asteroid impact.

There are also gravity-fed means of cooling conventional reactors, but I wouldn't call any of them fool proof. Liquid sodium seems like the best bet to me from a safety standpoint, at least as far as using up existing nuclear material. Thorium reactors show promise as well, but since we have a ton of reusable nuclear material liquid sodium would be my choice from a practicality standpoint.

One MIT Engineer to Another

[Anonymous Coward]

I am an MIT trained nuclear engineer than specializes in Probabilistic Risk Assessment. The first thing we should note is the PRA has had many benefits for the nuclear industry. Once you calculate the risk, and understand the contributors, you understand how to make things safer.

http://mydocs.epri.com/docs/CorporateDocuments/SectorPages/Portfolio/Nuclear/Safety_and_Operational_Benefits_1016308.pdf

The thesis of this article has a few problems, though the conclusion isn't horribly off base. The first problem is that he believe probability theory was applied to ignore the risk of the tsunami. The opposite is true. In fact, probabilistic hazard assessment of the tsunami showed the site to be horribly under prepared in 2006 (10% chance of exceeding the design basis in 50 years or about 1 in 500 per year [which is high for nuclear reactors]). There were even more studies in later years before the tsunami hit. This was just plain bad management and shows what may happen when you ignore updated risk information.

http://enformable.com/2011/10/new-exposed-scandal-shows-tepco-calculations-in-2006-showed-probability-of-worst-case-tsunami-dramatically-increased-10-over-50-years-utility-took-no-countermeasures/

The main point though, that no matter how unlikely a single event is (in this case a tsunami), you ought to have some countermeasures, is not bad. That is why PRA is used in combination with deterministic defense-in-depth measures at well designed, operated, and managed nuclear reactors. Mobile emergency diesels should be available to all reactors and are in the United States. This is a feature that Fukushima did not have. At the end of the day though, ceoyoyo is right. Even with multiple methods of cooling a reactor, you can not eliminate the possibility of core melt and release of radionuclides to the public. You can only ensure the release is acceptably infrequent. This brings us full circle to the fact that using probability theory to focus on the high risk stuff is good and that Fukushima failed to do this.

That being said, even in the case of passively cooled reactors such as fast reactors, massive earthquakes (1 in 1,000,000 per year or less), could destroy the water tank or piping required for passive cooling to take place. I would argue that while one should not ignore earthquakes and other rare external events below a certain probability. The burden would be onerous to use events below 1 in 100,000 per year as a design basis. This is in line with previous regulatory safety goal and can be seen in use in debate over the transition break size rule. A plug for my journal article is below. If you are wondering which author I am, the hint is that I am not the NRC commissioner.

http://www.sciencedirect.com/science/article/pii/S0029549311008284

Re:Reckless!

[lgw]

From what I understand pebble-bed reactors don't even count on gravity-fed cooling. The reaction simply stops if it gets too hot, effectively setting a maximum temp that won't burn through concrete.

Of course, pebble-bed was more about demonstrating idiot-proof safety than practical power generation, but it would actually work just fine (if not as cheaply as more sophisticated designs).

Re:Correct

[NeutronCowboy]

Molten salt reactors introduce a new problem though: the material is highly corrosive, and there are few materials that have even been tested that could provide a proper lifespan to the reactor. Furthermore, maintenance on the entire primary loop is like maintenance on the containment vessel for water cooled reactors: you just don't do it. This means that while the system is safer from a human fuck-up perspective, it presents brand-new engineering, construction and maintenance challenges.