Japan To Create a Nuclear Meltdown

Taco Cowboy writes "Japanese researchers are planning an experiment to better understand what transpires during a nuclear meltdown by attempting to create a controlled nuclear meltdown. Using a scaled down version of a nuclear reactor — essentially a meter long stainless steel container — the experiment will involve the insertion of a foot long (30 cm) nuclear fuel rod, starting the fission process, and then draining the coolant. The experiment is scheduled to take place later this year."

Comments

Great

[StripedCow]

What could possibly go wrong?

By the way, didn't they have to hand in their license to do nuclear stuff already?

Re:Great

[Stargoat]

What could possibly go wrong?

I believe that's what they want to find out.

Re:Great

[Sarten-X]

And, it should be noted, they want to find out in controlled conditions with sufficient protective equipment in a facility explicitly configured for this kind of situation. This is science.

Re:Great

[ebno-10db]

This is science.

The problem is that it should have been done decades ago. You're supposed to test failure modes before you declare something safe. That's doubly true of something as potentially dangerous as nuclear meltdowns.

Re:Great

[Nemyst]

The lizard pen of that facility is apparently really cool. A bit big for the lizards, though, and I'm not sure why it's so close to the reactor...

Re:Great

[KDN]

Actually the US did conduct such tests back in the 70's and 80's. Look up the LOCA (Loss Of Coolent Accident) test program done by the NRC. If memory serves, they scaled it up to 10% reactor capacity. Note: I believe these were what was assumed to be worse case accidents: reactor going full power and suffering a double gullotine cooling pipe failure. I don't know if they ever tested a reactor that has been SCRAM'ed, but still generating heat from short lived isotopes. That is what happened in Japan.

Re:Great

[amorsen]

Good luck with that. IDB Reference Characteristics of LWR Nuclear Fuel Assemblies from the 1996 Integrated Database Report (copied from Nuclear Tourist) mentions a fuel rod assembly containing 185 kg uranium. In contrast, Little Boy which destroyed Hiroshima contained 64 kg uranium, and that was certainly not a 100% efficient fission reaction.

It is not realistic to design nuclear power plants to withstand the maximum energy you could get out of the reaction. That would kill off the nuclear industry.

Feel free to start discussing whether it is realistic to get all the energy out of the 185 kg uranium. You can argue that it is less highly enriched than bombs, and that it is entirely unlikely that uranium which is mostly U-238 is going to suddenly decide to fission. I completely agree, but then we are no longer protecting against the maximum energy that could get released.

Re:Great

[brausch]

It was done decades ago.

Pacific Northwest National Laboratory conducted in-reactor experiments that involved total fuel failure in a controlled environment. The series of experiments took place in the Canadian research reactor NRU located at the Chalk River Laboratory in Ontario. There were a series of experiments over about a six year period in the 1980s.

Three Mile Island's accident was the trigger for this research program. There was financial support for the project from the US, Canada, Japan, Germany, and a consortium of around 20 other nations.

The most severe of the accidents that we simulated involved simulating a Loss Of Coolant Accident (LOCA) that resulted in fuel rod cladding failure (including melting in the worst cases) to try to recreate the near total blockage of coolant flow in the fuel bundle. There were around 200 thermocouples in the test rig, along with lots of flow meters, etc. The idea was to gather enough detailed data to allow the regulatory agencies to properly evaluate the computer programs developed and used around the world that would try to predict the test results.

We actually used full 12-foot commercial reactor sized fuel rods. The reactor had only a 3-meter long core so our experimental containment actually stuck out the top and bottom of the regular core. We had a tiny bundle of rods, fully instrumented, inside a specially designed containment and the whole thing was then inserted into a process tube inside the reactor.

You can do a Google (or other) search using the words "pnl nru loca" and you can find a lot of information.

I was the lead programmer for the data acquisition and control system for the experiments.

Re:sure

[jalopezp]

It's possible that because of some failure, their test reactor does not melt down.

Re:Good Idea

[DeathToBill]

I'm curious how much they'll be able to infer, though. Nuclear reactors (and reactions) are viciously non-linear. If you make it too small, you'll get no (self-sustaining) reaction at all. From that point up, the nuclear reaction scales with volume, thermal transfer probably scales with surface area, and other material properties and deformations will scale anything from linear to fourth power (at least).

So trying to infer anything about full-scale reactors from this is going to rely on a lot of modelling to tell you how the results will be transformed into real-world performance. Since it's that model that you're trying to investigate, there are lots of potential pitfalls.

Re:Good Idea

[BigT]

It won't tell you much about what happens when the fuel all melts and starts pooling at the bottom of the reactor of course

They already did that experiment, but it was poorly instrumented.