Friday, March 18, 2011

Going Nuclear II

Back in January I wrote post, badly, about a problem with Nuclear Power Plants that no one seemed to be addressing which was that the huge amount of water needed for a Nuclear Power Plant to operate limits where they should be placed to the coastlines of the Oceans and Great Lakes. Going Nuclear

The nuclear crisis in Japan underscores this problem in a way I hadn't even thought of.

As of today it looks like the Japanese reactors will be brought back under control thanks to first of all 50 engineers who volunteered their lives (they've taken lethal amounts of radiation in order to keep the plant from melting down). Second to the huge amount of sea water that the fire departments and army were able to pour onto the reactors.

Because the reactors were built right on the coastline the Japanese were able to flood the reactors keeping them cool enough not to meltdown while power could be restored to the cooling pumps. Because of this action it looks like the high level radioactive fallout will be contained to an 18 mile radius. (This is all subject to change as the reports from there change hourly).

Looking at the Japanese Nuclear Crisis, it seems obvious that any new reactor built in the US (or anywhere really) should take the knowledge learned from this crisis and apply it to the design.

Unfortunately, from what I am hearing, this is not the case. They are looking at what happens if an Earthquake of historic size hits a reactor but that doesn't address the two basic problems.

First, the current reactors have active pumping systems to cool the core, so if something goes wrong and electricity can't power the pumps you get a situation like you have in Japan. It doesn't take a historic earthquake to make the pumps lose power. The HB Robinson plant in South Carolina was shut down twice in six months because the contractor used the wrong size electrical wire when upgrading the pumps.

Any new reactor needs to have a passive control system to cool the core in case of an emergency, or we will get another crisis like Japan.

Second, there needs to be a system in place to cool the entire plant in case of disaster. In Japan they came up with the plan to flood the reactor with seawater on the spot. They should have had the equipment in place for last ditch effort when the plant was built.

I am fairly pro-nuclear power, it has a lot to offer, but in order for it to be a viable alternative to fossil fuels these are seem fundamental engineering problems that need to be addressed.

By Darrell B. Nelson author of I KILLED THE MAN THAT WASN'T THERE

1 comment:

Stephanie Barr said...

Couple of things.

First, I agree with you. A passive system for safety is always best (we call it "fail operational, fail safe" here in the space world when we were actually insisting on this). What that means is that "shutting down" a reactor means it needs to actually shut down so it stops producing heat. This can be done, but it might mean that bringing it back on-line is a pain. Well, I think it goes without saying that that's better than never being able to shut the damn thing down. This is done with control rods sufficiently to shut the chain reaction down - if we're pumping tons of water through to keep it cool, that's not just residual heat - that means we still have a chain reaction going. Once it's down, no more heat except for minimal radiation.

Hence the boron they're talking about adding (a very effective control rod material) is intended to do just that since it absorbs radiation and shuts the process down. As soon as all cooling systems have failed, actual shut down of the process (which could be done passively) should take place (preferably with a passive deluge trigger to neutralize the residual heat).

But I digress.

Secondly, although I'm entirely with you on the bravery and heroic efforts of the crew working the reactors, I don't know that they've all had lethal doses. There are multiple types of radiation and, unless all the measured radiation has been gamma (and most of the products listed have beta radiation as the main by product), their suits and good practices can do a great deal to reduce the action doses they receive. There's also no telling that it's the same fifty the whole time. And they spent considerable time in the control room which would be shielded even against gamma radiation.

Most of the radioactive particles that are likely to have been released are unlikely to do much damage to people unless inhaled or ingested. Most of that radiation given off as beta or alpha, although more damaging internally, can't penetrate the skin. Gamma goes right through you, but it's the least hazardous except in great quantities.

I'm not making light of the challenges in work there. The Japanese, in my opinion, haven't made light of them either, going to efforts we would never go through on this side of the pond (and getting criticized for it anyway). But this panicking is stupid and over-blown. Chernobyl was a real issue with real lethal doses many hundreds of time worse than this (2 million mSi for days rather than 1000 mSi for short periods of time) and it didn't clear out cities hundreds of miles away. Hell, they kept using Chernobyl reactors until 2000. There is no comparison, seriously.