The pressure within the core requires that whatever cooling water (distilled or from the sea) they are going to use be inserted into it at a higher pressure, right?
I don’t know if a “manual” system (engineers on a treadmill?) can deal with trying to inject water (according to the article linked by Eleusis, in post 73, above) against a thousand psi (which, if I read that correctly, is the operating pressure under normal conditions). You may need high powered pumps for that…
Perhaps a bit rah-rah, but you may find the linked article from an MIT NukEnginteresting. AFAICT, he’s only addressing hazards from a reactor loss of coolant accident, not any potential hazards from the SFP. I also hasten to add that, while the linked opinion article is from a claimed Nuclear Engineer, I doubt it reflects the views of MIT or their Nuclear Engineering department.
No, the news articles I’ve seen are very clear on this point, the level jumped from microSievert range to hundreds of milliSievert/hr range. Latest news I saw says they’re going to “allow” workers at the plant to be exposed to 250 mSv, up from the normal limit of 100 mSv, which allows them to work at the plant for just over 30 minutes rather than 15.
seeing news that only 50 or 70 workers are left at the plant due to high radiation levels.
So do I understand correctly that the “spent” fuel rods still generate enough heat to melt down by themselves unless immersed in water?
I thought the same thing when I read the article this morning. I’m also used to thinking in terms of rem, so I did the same conversion and also came up with 40 Rem/hr, and thought, “Holy shit!” :eek:
When I was in the Navy, we were limited to just one-tenth the maximum allowable whole-body dose of the federal limit for radiation workers, so we would reach our maximum allowable annual dose (500 mrem) at that rate in just 45 seconds. (We were also limited to a maximum quarterly whole body dose of 300 mrem.)
Perhaps not melt, but they can certainly heat up to the point that the fuel cladding catches fire (releasing radioactive waste), depending on how long it’s been since the fuel rods were removed from the core. Ultimately, spent fuel rods will cool enough to be removed from the pool and be reprocessed to obtain usable fuel, or be processed as high level nuclear waste for disposal. It takes a few months before this is possible, though.
In theory that’s true. Not so sure in practice. I referenced this study yesterday: http://www.sar-net.org/upload/s2-6.pdf Zirconium fuel rod cladding was electrically heated to up to 1500 deg C and air or steam blown through to see what happens. It slowly oxidised but didn’t start a self-sustaining fire or anything like it. I think zirconium needs to be more finely divided to burn. For this reason I’m a little suspicious of reports that the reactor 4 fire was a burning zirconium fuel pool fire. I’ve read a couple of reports attributing it to burning lubrication oil.
Greg Palast on Emergency Coling Systems:
the International Nuclear and Radiological Event Scale, 1 to 7, is used to rate accidents.
Three Mile Island is a 5, Chernobyl is a 7.
no official rating has been given for Japan accident. Japanese officials on Saturday suggested it was a 4. French officials (a nuclear power friendly nation) have suggested a 6.
it is at least a 5 from what has happened.
radiation has now been detected in Tokyo.
Yeah, I read the same thing (i.e. that it’s between a 5 and 6 right now). As for the radiation in Tokyo I read that there was some trace radiation detected in a water sample (far below harmful levels) but that in subsequent samples no radiation above background was detected. Do you have a cite confirming that additional radiation is being detected in Tokyo?
-XT
Very interesting paper, matt, thank you for the cite. Surprising how much the zirconium corrosion varied depending on the gas composition and temperature, and when those were varied.
More links to chew on. A further plug for Eleusis’s mention of MIT’s NSE Nuclear Information Page here. They’ve a string of quite informative posts on the Fukushima situation. I found their descriptions to be very well written, concise, yet with enough information to be informative and a clear calm tone.
For those who have insomnia and need help sleeping, the NRC’s NUREG-1738 report, Technical Study of Spent Fuel Pool Accident Risk at Decommissioning Nuclear Power Plants may be found here. It is a very lengthy report, and as such is about a 20MB .pdf. Robert Alvarez, et al’s report, Reducing the Hazards from Stored Spent Power-Reactor Fuel in the United States that took a much more pessimistic line on the hazards of spent fuel fires may be found here. Also a .pdf, but much smaller. Obviously these earlier reports don’t have the benefit of knowledge from the study that matt cited. (Which leads me to the question, has there ever been a zirconium fuel cladding fire in Western nuclear facility operations? And if so, what was the nature of that accident to get the cladding to ignite, that was missing in the zirconium oxidation study?)
A question for the multitude: what is then causing the elevated radiation levels at the plant that caused many of the workers to be evacuated? I understand from the MITNSE post here, that initial elevated radiation levels were probably caused by, according to the post:
But radiation levels at the plant are have continued to spike and fall, leading at one point to workers being evacuated from the plant. What mechanism is causing these increased radiation levels, if it isn’t a spent fuel fire, (Thank God), and if the primary containment for the reactors haven’t been breached?
CNN was quoting a Japanese spokesman that a white cloud over one of the buildings may have been caused by a breach in the containment vessel.
From reading the very informative posts from robby, matt, Exapno, and others, I know that the word “containment” may refer to many different subsystems of the reactor installation. It would be nice if they mentioned which part is supposed to be damaged.
Perhaps it needs to be reemphasized that the damage and loss of life at Fukushima, in any but the absolute utter worst case, is tragic but will remain very, very minor compared to the rest of the damage caused by the tsunami and earthquake. Moreover, it is impressive how well 40 year old designs are coping with one of the largest earthquakes in recorded history coupled with a very large tsunami. Radiation certainly grabs peoples’ attention.
my comment was based on parts of a news release from this morning (in USA)
TOKYO (Reuters) –
…
Early in the day another fire broke out at the earthquake-crippled facility, which has sent low levels of radiation wafting into Tokyo in the past 24 hours, triggering fear in the capital and international alarm.
…
Officials in Tokyo said radiation in the capital was 10 times normal at one point but not a threat to human health in the sprawling high-tech city of 13 million people.
…
First you could have a intermintent leak. Pressure or temp gets a bit high, leak gets much worse, causes the temp or pressure to fall again and leak stops/greatly decreases.
Or you could have an area where some radioactive material has accumulated, like say some contaminated water in the bottom corner of one of the mostly destroyed buildings. If the wind temporarily shifts or a gust comes along, that could greatly increase the rate at which that source is releasing radioactive material into the environment. Wind goes back to normal and rate drops back down.
In Germany they tested the diesel generators at one of the older plants (Biblis A or B, not sure which) and actually noticed they would never have generated any electricity at all, because they had forgotten to install the coupling for the driveshaft. :smack:
Another complication (as I understand it, lots of semi-contradictory, confused sources, etc) is that the “spent” fuel rods in the #4 storage tanks are not actually spent, having been taken out of the reactor and filed there while the reactor was shut down for some reason or another.
That’s correct. They were taken out because reactor 4 was undergoing routine maintenance. So they are not “spent” rods.
The one I’m most worried about is reactor 3. There have already been statements saying that the containment was damaged, and reactor 3 uses MOX rods, which means they contain plutonium.
If that stuff gets outside the containment you can stop worrying about the millisieverts.
I dont think thats true.
Now, if you wanted to compare a reactor that had never been run (or run for a very short period of time) that suddenly blew up/caught fire, yes, the one with some plutonium would be worse.
But once you’ve run a reactor for awhile, its all the other really nasty stuff thats way more radioactive (and sometimes biologically active, ie it gets absorbed chemically/biologically into your body) that you have to worry about. Stuff that makes plutonium look downright harmless.
Now, its possible that a running reactor with plutonium in the fuel mix has WAY more of those other really nasty things in it, but I don’t think so.
When reading press releases that imply there is some “safe” level of radiation exposure, or some level that is too low to cause damage, it’s worth noting that the National Academies of Science committee took the view that there is no such thing, at least not per se. The BEIR VII (Phase 2) committee endorses the LNT model (Linear, No Threshold).
The short layman’s version:
[ul]
[li]Harm to health is dependent on exposure (linear…more=bad, less=less bad)[/li][li]There is no safe minimum exposure (threshold)[/li][/ul]
This has two implications for the discussion. Firstly, it is true you are unlikely to get cancer from low levels of exposure – lottery-winner unlikely for low levels, incalculably unlikely for very low levels. Secondly, while it is reasonable for various authorities and news sources to characterize the harm from low levels as “negligible,” minuscule, or otherwise of little account, it’s somewhat disingenuous of them to characterize the situation as having “safe levels” as if there’s some line you can stay under and be completely confident. There’s randomness involved and there’s a theoretical chance from any sort of exposure. Of course, that includes normal environmental exposures like going outside (or staying indoors for that matter).
The takeaway: radiation levels can be low enough not to worry about, but it irritates me when it’s presented like some bad SF movie where you can stand in the radiation for 29 seconds and be safe if 30 seconds is the “lethal dose.”
Thanks for the hypothesis on the intermittent radiation spiking, billfish. As the quoted material indicated, the workers are back at the plant, continuing to control the situation.
On the other side of that argument are proponents of Radiation Hormesis. I’ll remain agnostic regarding Hormesis or the LNT model, as I don’t believe we have a very good idea of the long term effects from widely scattered, very low levels of ionizing radiation. I would prefer not to experience any more of it than I had to, but unlike the NAS, I am unsure whether cancer rates scale linearly with decreasing radiation. The Reports from the UN Chernobyl Forum Expert Groups go into great detail as to the epidemiology and environmental effects of the disaster as of the middle of 2006. Health Effects of the Chernobyl Accident and Special Health Care Programmes, a report from the CFEG, “Health” can be found here. (.pdf) A similar report from the CFEG, “Environment”, ENVIRONMENTAL CONSEQUENCES OF THE CHERNOBYL ACCIDENT AND THEIR REMEDIATION: TWENTY YEARS OF EXPERIENCE can be found here. (Also a .pdf, sorry for the all-caps in the title.)
Short version, I would’ve expected to see a lot more cancer incidence and deaths from the radiation dumped on Northern Ukraine/Belarus than have shown up so far. Accordingly, I don’t know how much the LNT model cited by Sailboat holds true at very low levels of ionizing radiation.