Fukushima: The myth of safety

[thriftyandboringinohio]

Re: Fukushima: The myth of safety

I'm not an expert, but my understanding is that the reason why spent fuel rods are stored near the reactors is because the spent fuel rods need the same thing as the reactors: high volumes of.... circulating purified water to keep temperatures down....

Last year I worked a nuclear power plant refueling project, and the plant's Chief Nuclear Officer made that exact point pretty dramatically at a large project meeting. Westinghouse was presenting the status of a certain portable water pump that had caused problems last refueling. Westinghouse had put a team of engineers to work and concluded that the pump would likely not be needed this outage, but they'd have it on site anyway just in case.

The CNO glared and frowned and said "I do not want to hear another word from Westinghouse about why this pump isn't needed. This is a nuclear reactor core that needs to be cooled the day before we refuel the reactor, and it will be treated as such during refueling and after it's in the spent fuel pool. Do you understand me?"

You coulda heard a pin drop as a hundred senior technical people waited the two seconds it took the Westinghouse guy to say "yes" and sit down.

[cjppjc]

Re: Fukushima: The myth of safety

Thanks for acting as a BS meter... can't read anything these days without being on guard.

+1

[c1ue]

Re: Fukushima: The myth of safety

Cancer and radiation is a tricky thing.

For one thing, it seems quite clear that it isn't any radiation that causes cancer, it is any radiation over a certain amount in a certain period of time.

For another thing, it appears highly variable due to genetics, lifestyle, and so on and so forth.

Ionizing radiation - that bugaboo that those seeking to alarm over radiation invoke - is something undergone by every person who goes up in altitude in a commercial flight.

The radiation dose received in a typical 8 hour international flight is comparable to over 10 years of 'background' radiation (40 milliSieverts vs. 3.5 annual mSv exposure).

If a pilot flies 1 international 8 hour trip per week, this works out to over 1100 years of annual background exposure per year (40 mSv * 2 * 50 / 3.5).

Now, if indeed radiation exposure/ionizing radiation exposure is linearly related to cancer, you'd think airline pilots would be dropping like flies from cancer.

But that doesn't seem to be the case:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1739925/

Incidence of cancer among commercial airline pilots

V. Rafnsson, J. Hrafnkelsson, and H. Tulinius

Department of Preventive Medicine, University of Iceland, Reykjavik, Iceland. Email: vilraf@hi.is

This article has been cited by other articles in PMC.


Abstract


OBJECTIVES—To describe the cancer pattern in a cohort of commercial pilots by follow up through the Icelandic Cancer Registry.
METHODS—This is a retrospective cohort study of 458 pilots with emphasis on subcohort working for an airline operating on international routes. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cancer cases were calculated on the basis of number of person-years and incidences of cancer at specific sites for men provided by the Cancer Registry. Numbers of separate analyses were made according to different exposure variables.
RESULTS—The standardised incidence ratio (SIR) for all cancers was 0.97 (95% confidence interval (95% CI) 0.62 to 1.46) in the total cohort and 1.16 (95% CI 0.70 to 1.81) among those operating on international routes. The SIR for malignant melanoma of the skin was 10.20, 95% CI 3.29 to 23.81 in the total cohort and 15.63,95% CI 5.04 to 36.46 in the restricted cohort. Analyses according to number of block-hours and radiation dose showed that malignant melanomas were found in the subgroups with highest exposure estimates, the SIRs were 13.04 and 28.57 respectively. The SIR was 25.00for malignant melanoma among those who had been flying over five time zones.
CONCLUSIONS—The study shows a high occurrence of malignant melanoma among pilots. It is open to discussion what role exposure of cosmic radiation, numbers of block-hours flown, or lifestyle factors—such as possible excessive sunbathing—play in the aetiology of cancer among pilots. This calls for further and more powerful studies. The excess of malignant melanoma among those flying over five time zones suggests that the importance of disturbance of the circadian rhythm should be taken into consideration in future studies.

Despite exposures which are literally thousands and tens of thousands normal exposure, the international pilots have overall cancer rates less than 20% higher than the average pilot, which in turn have a slightly less than average cancer incidence rate.

There is a very significant increased risk of skin cancer, but the overall rate of cancer is actually normal outside the skin cancer outlier.

[debu]

Re: Fukushima: The myth of safety

Talk of airplane flights and MRTs and bananas are straw men arguments. Funny how mention of the risks of internal contamination, which is far more dangerous, is somehow neglected. Strange that.

[c1ue]

Re: Fukushima: The myth of safety

Talk of airplane flights and MRTs and bananas are straw men arguments. Funny how mention of the risks of internal contamination, which is far more dangerous, is somehow neglected. Strange that.

Perhaps you can elaborate on these risks, after all, we've only had several hundred nuclear tests, including many aerial ones.

The entire Pacific Rim should be a cauldron of cancer due to the presence of radioactive elements including plutonium, strontium, cesium, and what not for over 4 decades - in air, in the water, in fish, in plants, and so forth.

[Polish_Silver]

Re: Fukushima: The myth of safety

How long do the rods need circulating water? I'll bet it's two years at the most.

[debu]

Re: Fukushima: The myth of safety

Perhaps you can elaborate on these risks, after all, we've only had several hundred nuclear tests, including many aerial ones.

Forgive my ignorance but are the public health risks posed by nuclear tests equivalent to those of three simultaneous meltdowns in nuclear power stations in close proximity to major population centers?

[davidstvz]

Re: Fukushima: The myth of safety

How long do the rods need circulating water? I'll bet it's two years at the most.

10 to 20 years before it can be reprocessed or sent to dry storage according to wikipedia.

I assume it needs circulating water the whole time (to keep the water cool by running it through a refrigeration unit).

[vt]

Re: Fukushima: The myth of safety

http://online.wsj.com/article/SB1000...pinion_LEADTop

[Polish_Silver]

Spent fuel pools

The wiki article on spent fuel pools seems fairly good:

1) rods are kept in the pools 10-20 years before being suitable for dry cask storage.

2) Water quality is important to prevent degradation of the cladding.

3) provision for circulating and cooling the water is needed

4) The rods do gradually cool down.

China is building a system to use the spent fuel to provide heat for desalination. This is an old idea promoted by James Lovelock. However, China seems to be the first place to actually use it.

The spent fuel pools are a security risk. According to "the nation" the Fukushima pools did not have back up water circulation systems.

The time needed to keep the fuel in the pools seems to be a technical and policy issue.

The Wiki Dry cask storage article mentions times from 1 year and up.


NRC on dry cask storage:
http://www.nrc.gov/waste/spent-fuel-...k-storage.html

(mentions 1 year in spent fuel pool)

My comment
The rods are kept in pools so long because alternatives are limited. The alternatives are limited
for political and legal reasons, not technical ones. The way things are going, China will be paid to
accept every one elses spent fuel and have free heat and hydrogen fuel in the bargain.

[c1ue]

Re: Spent fuel pools

Forgive my ignorance but are the public health risks posed by nuclear tests equivalent to those of three simultaneous meltdowns in nuclear power stations in close proximity to major population centers?

You tell me: the largest hydrogen above ground test was the Tsar Bomba:

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

It was 1,400 times stronger than Hiroshima and Nagasaki combined: 50 megatons.

It weighed 27 tons.

The largest US bomb test was Castle Bravo: http://en.wikipedia.org/wiki/Castle_Bravo

This bomb had a yield of 15 Megatons, and weighed just under 12 tons.

Overall there have been over 500 above ground nuclear tests totaling over 450 megatons, plus the 2 'field tests'.

http://www.johnstonsarchive.net/nucl.../wrjp205a.html

Nevada alone had over 100 above ground nuclear tests from 1951 to 1992 - there should be concentric rings of cancers extending outward from the Nevada desert into Los Angeles, Las Vegas, Phoenix, San Francisco, and so forth by now.

[davidstvz]

Re: Spent fuel pools

That depends greatly on the dynamics of the bombs tested though. Hydrogen bombs get most of their energy from fusing light isotopes of helium into normal helium (if I understand right). I could be entirely wrong, but I think the fusion reaction itself is entirely clean. However, there is a fission reaction used to get the fusion reaction started, hence there may be some amount of radioactive material dispersed in a fusion bomb, but not nearly as much as if you simply scaled a fission bomb to the same megatons as a fusion bomb. The fusion reaction may emit some dangerous particles during the blast itself, but once finished, the only radioactive material to spread should be whatever limited amount was in the fusion trigger. Presumably less than the original fission bombs... although that is just a WAG.

[c1ue]

Re: Spent fuel pools

I could be entirely wrong, but I think the fusion reaction itself is entirely clean.

If you have 2 deuterium atoms, and fuse them, then in theory this should be clean.

If you take a fission bomb and surround it with tons of lithium or deuterium, you don't have just 2 deuterium atoms. Even after the first fusion, there are going to be a cascading number of secondary and tertiary reactions. Sure, you probably don't wind up with strontium, or at least not much, but you still get all sorts of other fun stuff.

Fusion bombs are much less 'dirty' relative to their megatonnage, but this is a far cry from clean.

[davidstvz]

Re: Spent fuel pools

c1ue, I found this on physics forum:

The main fusion reaction under consideration is "D-T" fusion:

D + T --> He4 + n + 17.6 MeV

The product isotope He4 is stable - so it is often said that fusion is
"clean" and doesn't produce radioactive species.

However, that neutron; the "n" ; receives 14.1 MeV worth of energy and
the next atom it hits will most likely become radioactive.

So D-T fusion is only "clean" if you look at just the first generation of
products. If you look one generation removed from the initial products -
then you are going to have radioactive species and fusion is not "clean".

In fact, fission gives you about 2 radioactive atoms per reaction, which
releases about 200 MeV worth of energy. Fusion gives you 1 radioactive
atom per reaction that releases 17.6 MeV of energy.

So in effect, on a per energy released basis; fusion is more than 5 times
more "dirty" than fission.

Dr. Gregory Greenman
Physicist

So it's specifically the neutrons ejected into the environment that turns many ordinary substances into radioactive isotopes. I'm sure many of them are very short-lived, but the ones with half-lives measured in years would make an area radioactive for an extended period.

[Polish_Silver]

Re: Spent fuel pools

Fusion bombs: Every H bomb uses a uranium fission bomb to produce the temperature and pressure needed to start fusion.
The fusion then releases energy which causes more fission. About half the released energy actually comes from fission processes. Not suprising, because Uranium has a far higher density of nuclear particles than hydrogen.

Fusion reactors: No one has even come close to building a practical fusion power source. So there is no way of knowing how "clean" the energy would be, or if there would be solid waste, gaseous waste, etc.