Why Fukushima Was Preventable • Hacker News Board

Re: Why Fukushima Was Preventable

#21

Post by uvdiv » Sun, Aug 19, 2012, 5:18 PM UTC

jimktrains2 wrote: post #4

esbwhat wrote: post #3

I don't think it's really relevant. The point is not that there is a way to have safe nuclear energy, the point is that the worst case scenario is catastrophic, and that I don't trust any company or government to do what's necessary, especially if they're strapped for cash.

That's not entirely true. There are a lot of new designs (i.e.: not BWR) that passively cool and shutdown without the input of any external energy. Also, molten salt reactors and fusion reactors won't be able to have catastrophic failure modes either.

There are a lot of new designs (i.e.: not BWR) that passively cool and shutdown without the input of any external energy.

That's true of some new BWR designs as well:

http://www.ne.doe.gov/np2010/pdfs/esbwrOverview.pdf

Claims 72 hours of passive heat dissipation -- the heat sinks are [giant] tanks of water inside the containment building.

The HN article mentions a passive cooling system in Fukushima Daiichi #1: a gravity-driven steam condenser (footnote #5). It failed when electric batteries failed, because it needed DC electricity to open valves. (I think this isn't the case in ESBWR).

The systems with limited functionality in the absence of power were an isolation condenser (in unit 1) and a reactor core isolation cooling (RCIC) system (in units 2 and 3). An isolation condenser takes steam from the reactor core, passes it through a tank of water to cool and condense it, and then feeds it back as water into the reactor pressure vessel. The flow is gravity driven (i.e., no pumps are needed). The system in unit 1 had a thermal capacity of about eight hours.

Re: Why Fukushima Was Preventable

#22

Post by pella » Sun, Aug 19, 2012, 6:44 PM UTC

"Black Swan Lessons on the Japanese Disaster .."

"We don't understand the world as well as we think we do and tend to be fooled by false patterns. We mistake luck for skills (the fooled by randomness effect), overestimate knowledge about rare events (Black Swans), as well as human understanding, something that has been getting worse with the increase in complexity." Nassim Taleb

http://www.cbsnews.com/8301-505125_162-40143642/black-swan-l...

Re: Why Fukushima Was Preventable

#23

Post by mjvandenbergh » Sun, Aug 19, 2012, 7:05 PM UTC

dctoedt wrote: post #20

My jaundiced view of civilian nuclear power is still colored by one of my most vivid experiences in the Navy nuclear reactor program. It came in the course of prepping for the [chief] engineer's exam, after two years of sea duty running reactor plants aboard an aircraft carrier. That in turn had followed a year of intensive academic and practical nuclear propulsion training. Our "coaches," all senior nuke officers, h…

The American nuclear navy is one of the classic examples of what process safety experts call a High Reliability Organisation. HROs are organisations that run dangerous systems susceptible to so-called "Normal Accidents" while having fewer such accidents than their competitors.

The main things that have been found to contribute to HROs are: A chronic sense of unease even in the face of normal operations - always be thinking of ways to improve safety. A separate engineering standards organisation that is not responsible for operations - i.e. they can order shutdowns without affecting their own job objectives in a way that a plant manager cannot. They do not tolerate the so-called "normalisation of deviance" (which is when out-of-range behaviour becomes accepted as people get used to it.).

Re: Why Fukushima Was Preventable

#24

Post by mjvandenbergh » Sun, Aug 19, 2012, 7:06 PM UTC

alberich wrote: post #12

_delirium wrote: post #2

Long article, but the best one I've run across explaining the inputs used to choose design tolerances, the advances in those methods over the years, and where the Fukushima design and later maintenance was and wasn't in accordance with best practices. The overall conclusion is that it was known by the early 2000s that the plant's worst-case tsunami estimate, used as its design basis, was no longer sufficient, given i…

I don't know Japan's geography, so, maybe it is possible for it to have tsunamis everywere. However, if there is some part of Japan's territory that is safe from tsunamis, wouldn't it be easier to just build those reactors there, and not in a place that is known to have tsunamis since, at least, the year 684 AD?

In general the west coast of Japan is much less susceptible to tsunamis.

Re: Why Fukushima Was Preventable

#25

Post by mjvandenbergh » Sun, Aug 19, 2012, 7:07 PM UTC

Retric wrote: post #19

jimktrains2 wrote: post #9

Earlier quoted context omitted.

Yes, I understand that you can't just turn them "off." It's easiest just to say that it's shut off if it's unable to do anything really. I think you missed everything in my previous post. All new designs passively cool. You can have safe (comparative to coal and gas) nuclear power.

I should have been more clear, a lot of designs passively cool the reactor / primary loop, but they don't have long term 100% passive cooling on the secondary loop. Though a counter example would be welcome.

No, you're right. They have a water pool that cools the secondary loop. That will need refilling after a few days, 72 hours for the ESBWR iirc.

Re: Why Fukushima Was Preventable

#26

Post by esbwhat » Sun, Aug 19, 2012, 7:43 PM UTC

jimktrains2 wrote: post #4

esbwhat wrote: post #3

I don't think it's really relevant. The point is not that there is a way to have safe nuclear energy, the point is that the worst case scenario is catastrophic, and that I don't trust any company or government to do what's necessary, especially if they're strapped for cash.

That's not entirely true. There are a lot of new designs (i.e.: not BWR) that passively cool and shutdown without the input of any external energy. Also, molten salt reactors and fusion reactors won't be able to have catastrophic failure modes either.

Fair enough -- I should have informed myself better before commenting/making judgements.

Re: Why Fukushima Was Preventable

#27

Post by Turing_Machine » Sun, Aug 19, 2012, 9:12 PM UTC

dctoedt wrote: post #20

My jaundiced view of civilian nuclear power is still colored by one of my most vivid experiences in the Navy nuclear reactor program. It came in the course of prepping for the [chief] engineer's exam, after two years of sea duty running reactor plants aboard an aircraft carrier. That in turn had followed a year of intensive academic and practical nuclear propulsion training. Our "coaches," all senior nuke officers, h…

Nuclear power has been in widespread civilian use in the West for over 50 years without a single nuclear-related fatality to a member of the general public (Chernobyl was a crap design that was never approved in the West). Plant workers have been killed and injured, yes, but even if you take them into account, the safety record for nuclear is still much better than any other source (coal mining isn't the safest job in the world, nor is working in oil and gas fields).

You know what worries me? The 75 million people who live downstream of the Three Gorges Dam.

Re: Why Fukushima Was Preventable

#28

Post by Turing_Machine » Sun, Aug 19, 2012, 9:16 PM UTC

esbwhat wrote: post #3

I don't think it's really relevant. The point is not that there is a way to have safe nuclear energy, the point is that the worst case scenario is catastrophic, and that I don't trust any company or government to do what's necessary, especially if they're strapped for cash.

Let's see. The plant was hit by:

1) Massive earthquake 2) Tsunami 3) Fire 4) Total loss of all power to control systems

Result: no one died from radiation exposure (a couple of guys died from heat stroke while fighting the fire).

Just what do you consider a "worst-case scenario"?