Comment by chrissnell | Hacker News Reader

Comment by chrissnell | Hacker News Reader

Parent Full thread

Are size and efficiency the most pressing issues to solve in nuclear power? I don't know a thing about nuclear issues but from the layperson's perspective, it seems like security is the biggest problem that keeps nuclear power from being used everywhere. These containers are essentially dirty bombs without detonators and must be protected as such. This might work for the military, where you could secure one on a restricted section of a FOB, but how would this work for a small town in Alaska, as the article suggests? Securing the site is only half of the problem, too. You also have to secure the supply chain for the nuclear material, as well as the disposal. The cost of disposal is another challenge. Imagine the difficulties of transporting the spent fuel from the Alaskan village.

These guys have a big challenge ahead of them but it would be quite awesome if they can pull it off. Prime power generation and the supply chain issues that its fuel entails is a huge and extremely expensive problem for the military. If you could safely build this in a CONEX, that would be impressive.

Commercial power reactors are very expensive initially (multiple billions). This is a huge barrier to entry for most power plants. So the thinking is if the size can be reduced so can the cost.

The military is interesting because they already have small reactors in submarines and ships. And they have access to the highest grade fuel because they don't have to follow power plant regulations. So it seems like if these modular reactors would be useful to them, they could easily adapt these reactors for land use.

This startup is hard to gauge because there's so few actual details about their design. For example, how are they going to use thorium as a fuel? You can't just use thorium without a strong neutron starter source or some other fuel engineering.

'It can burn any fuel' is just code for 'we have no real core design yet'. But it doesn't matter, because no nuclear fuel is significantly better than any other, and they're all thousands of times better than alternatives.

Thorium is always used in mixed cores. An accelerator-driven thorium reactor will contain uranium from breeding even if no uranium is ever loaded into it.

There are core designs for low enriched uranium loading, mixed thorium loading, and spent fuel loadings. Have to make sure a fuel design works before it's claimed to work.

With 12 years of burnup? I've been having trouble getting burnup codes to handle thorium. What are you using? Apparently I should be using Serpent.

But anyway, 12 years is too long, even if it's feasible. Something like 4 years should be better, due to the learning curve on these. For instance, think of a reactor in the field as a ship on a long trip while technology at home continues to improve

http://en.wikipedia.org/wiki/Wait_Calculation

Edit: The lower the enrichment, and the lower the excess reactivity, the better.

The concept is to start small to overcome cost and regulatory barriers more quickly and for less.

And yes, we kick start using thorium with low enriched uranium or spent fuel to build up U233. Then we just keep reusing the thorium fuel over multiple refueling periods without reprocessing or separations until it is depleted.

I may be naive, but are there really bad actors lurking the world that a) have the resource to pull off such a crime, b) be able to get away with c) not already have means to get what ever it is they want?

To take a stab at your hypothetical situation, the small town in Alaska has multiple armed guards 24/7 as well as centralized offsite monitoring. Protocols in place to alert local authorities which have protocols in place to alert state authorities, etc. The overhead will be covered by excess efficiencies in adopting such a system.

Exactly right. Reactors are not attractive targets and this is very robust.

More importantly, 9/11 hit the WTC. When it did everyone immediately said "imagine if they'd hit a nuclear reactor".

But they didn't. They could've, but they didn't (and it also wouldn't have done very much damage). The reality is that even at the largest conceivable scales, nuclear security as implemented is not threatened by violent terrorism or direct action, so much as leaky side-channels (scientists selling off isotopes on the side).

> essentially dirty bombs without detonators and must be protected as such.

No, it's completely wrong. That's not how a nuclear plant works. And as you can see, a nuclear plant does not "explode" when it goes amok. The chain reaction is very tightly controlled and there are multiples redundancies in case things don't work as expected.

"dirty bomb" is a radiological weapon, not a fission/fusion weapon, and is exactly what detonating explosives (or H gas, or whatever) inside a commercial power reactor or RTG would be.

Except that a dirty bomb is designed to maximize the hazardous effects of such an event while a reactor is designed to minimize the hazardous effects of such an event.

No, a dirty bomb is mainly designed to maximize fear, not hazard. Once its gone off, telling people it was safe is probably not going to work very well.

Nuclear plants certainly do "explode" when things when wrong. I assume you used scare quotes because you were thinking of a nuclear detonation, but there was plenty of damage done by the non-nuclear explosions at Chernobyl and Fukushima, to cite the most famous examples.

You are right that there are explosions, but it isn't an explosion like an atomic bomb. You understand the difference, but unfortunately there is a fundamental misunderstanding for the general public that a reactor could function like a bomb. There just isn't the energy density to do that.

There was physical damage to structures at Fukushima but that didn't cause any real damage outside the plant or releases. The releases were leaks elsewhere (which were still not huge compared to natural radiation levels).

Chernobyl was due to a reactor literally geared for instability (search rbmk void fraction for details) in the Soviet union. It had no containment around the reactor. So a basic structure around the reactor would crumble with an explosion. But it wouldn't contain that much regardless since it wasn't designed to, and they frankly were arrogant and didn't care much about safety precautions.

As to the plenty of damage from Chernobyl, here's the facts: it has been highly studied over almost 30 years, it is a nature preserve, people who refused to evacuate still live there healthily, and they still operate a reactor on that site. Here's an article which examined and summarized the largest and most reputable medical studies on the Chernobyl aftermath. I was genuinely surprised myself. http://www.thingsworsethannuclearpower.com/2012/05/things-wo...

Actually Chernobyl was (partially) a nuclear explosion. Lots of misunderstanding about this, even among nuclear engineers.

Go on, my understanding is that the "explosion" was basically a steam pressure explosion which blew the top off of the reactor, if that is incorrect do you have a reasonably easy to understand source?

There were two explosions - first was a steam explosion followed 2 or 3 seconds later by another more powerful explosion - with the cause of the latter still being debated. However, one theory does describe it as follows:

"However, the sheer force of the second explosion, and the ratio of xenon radioisotopes released during the event, indicate that the second explosion could have been a nuclear power transient; the result of the melting core material, in the absence of its cladding, water coolant and moderator, undergoing runaway prompt criticality similar to the explosion of a fizzled nuclear weapon."

http://en.wikipedia.org/wiki/Chernobyl_disaster#Experiment_a...

NB I'm in the process of reading *"Atomic Accidents - A History of Nuclear Meltdowns and Disasters: from the Ozark Mountains to Fukushima" - but I haven't got to Chernobyl yet....

http://www.amazon.com/Atomic-Accidents-Meltdowns-Disasters-M...

Arnie Gunderson from Fairewinds makes the case that the explosion in fuel pool of Unit 3 at Fukushima was a detonation (faster than the speed of sound) and not a deflagration (speed of sound). A plausible reason was a initial hydrogen explosion in the pool distorted the fuel and initiated a moderated prompt criticality. http://www.fairewinds.org/gundersen-postulates-unit-3-explos...

"It is not a bomb. A bomb is a prompt fast criticality." http://www.fairewinds.org/fukushima-daiichi-the-truth-and-th...

In the 50s the US did an open air experiment called Borax - Safety Experiment on a Boiling Water Reactor, where they blew up a reactor. http://nukeprofessional.blogspot.com/p/videos-moderated-prom...

Except you just have to look at Fukushima to see that things can still go badly wrong, resulting in a meltdown of 3 reactors. And this happened in arguably one of the most tightly regulated and technologically advanced countries in the world.

I live in Japan and I don't consider that the outcome was as catastrophic as the media said it was (they are always ready to jump on the apocalyptic trigger). Everything went wrong (even the backup generators as they were blown away by the tsunami) and it was still reasonably contained and the levels of ambient contamination are nowhere as high as they initially predicted.

EDIT: > most tightly regulated and technologically advanced countries in the world.

Let's drop this kind of argument here, there are many things which are not technologically advanced at all in Japan. Like the fact you can't even use a credit card to pay in most places. This is really old.

Also if there's any lesson here, it's that government intransigence is the real threat here. They don't want to build new reactors, they don't want to shut down old ones, but they still need electricity too.

And of course consider the scale - something like 8,000 people died from that tsunami. Oil refineries burned for hours (how much heavy metal got dumped into the ocean and soil?)...how many people did Fukushima actually kill?

> how many people did Fukushima actually kill?

Hey, we already know the answer. No-one. Not even the guys who went and exposed themselves to high doses of radiation to keep the reactor under control. And people who may have been contaminated are being strictly followed for potential leukemia and other cancers. Following the events, I'd say the risks regarding the nuclear power were relatively well managed.

No, there are other lessons too. Read the official report.[1]

"For all the extensive detail it provides, what this report cannot fully convey – especially to a global audience – is the mindset that supported the negligence behind this disaster. What must be admitted – very painfully – is that this was a disaster “Made in Japan.” Its fundamental causes are to be found in the ingrained conventions of Japanese culture: our reflexive obedience; our reluctance to question authority; our devotion to ‘sticking with the program’; our groupism; and our insularity.

[1] https://www.nirs.org/fukushima/naiic_report.pdf

> Let's drop this kind of argument here, there are many things which are not technologically advanced at all in Japan. Like the fact you can't even use a credit card to pay in most places. This is really old.

More salient is the fact that the country has two different electric standards in different parts of the country, as this contributed directly to the problem.

Wrong, perhaps, but 'badly' wrong? Despite the accident, building Fukushima saved lives and reduced atmospheric pollution relative to other power sources.

Part of the reason we haven't improved reactor designs as rapidly as we should is due to irrational fears surrounding nuclear power. In other words, such fears have to some extent been a self-fulfilling prophecy.

The fears aren't so irrational. They reflect the fact that we don't know how to assess and manage risk over the kinds of timescales required to safely handle nuclear waste.

After a couple of hundred years the waste is no more radioactive than the ore from which it came.

Although the fear-mongers never mention this,"long half-life" means "less radioactive". By definition.

1) Massive earthquake, followed by

2) Tsunami, followed by,

3) Complete loss of power to all control systems, followed by,

4) Gas explosions and core meltdown.

Pretty much the worst possible scenario, and yet no member of the general public was killed from radiation exposure.

Just how safe do you want something to be?

If it still survives 5) terrorist plane crash on the core, 6) Meteor impact, maybe people will feel a little less paranoid about nuclear energy :)

I agree with your comment, I'm constantly baffled by people who claim Nuclear Power is not safe.

Except you just have to look at Onagawa to see that things can still go exactly right.

http://thebulletin.org/onagawa-japanese-nuclear-power-plant-...

The cause of Fukushima was complete and utter corporate (at TEPCO) and regulatory failure. I would argue against "tightly regulated"; on paper it may be, but in practice it obviously was not or we wouldn't have been in this situation in the first place.

Reply on news.ycombinator.com