OT: Chernobyl metal content uranium

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tour of the area.
Kind of sobering but interesting.
Karl
Reply to
Karl Vorwerk
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...wow... It really makes you think about the genie in the bottle.
Reply to
George
There was no bottle! They built that plant without any containment building...and paid the price. They also neglected to learn from a similar accident that happened to a somewhat similar British plant (Windscale
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decades ago.
Vaughn
Reply to
Vaughn
They opted for a graphite system if I recall. There was an interesting National Geographic about Chernobyl a few years back and they showed, for example, the graveyard of helicopters and equipment that had to be abandoned because it was too hot to be used again. In the commentary they noted that people had been sneaking in and stripping parts off to sell in the black market.
Reply to
George
Notice that all the radiation readings in the article are in micro-Roentgens, and the average for the area is now only 6 uR above global average background.
As a reality check, the LD50-30 dose is 500 Roentgens, or about 19,000,000 times higher. That's why the young lady doesn't fear to tour through the area. As she says, people fear radiation all out of proportion to the actual risks.
A good factual description of radiation effects and risks can be found here:
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Here's a snippet. (Note REM is Roentgen Equivalent Man and is equivalent to whole body absorption of one Roentgen of gamma radiation or ingestion of an alpha emitter with an output of 0.05 Roentgen. Alpha can't penetrate the skin, but it does more damage if it gets inside the body than gamma or beta.)
Begin quote:
4.1 Risk Comparison Since many persons are particularly fearful of radiation, it may be helpful to compare the risk from radiation exposure to some other risks encountered in everyday life. Based on the straight-line model, a worker exposed to 1,000 millirem (one rem) per year for 30 years would lose about 30 days of life expectancy due to increased risk of cancer. This is comparable to other "safe" jobs. For comparison, the loss of life expectancy for some other risks is given below.
Job or Other Risk Days of Life Expectancy Lost
Manufacturing 43 Agriculture 277 Construction 302 Coal Mining 1100 Being 30% overweight 1300 Being President of the U.S. 1861 Being an average male smoker 2153
To put it another way, statistically the risk from one millirem of exposure is approximately equal to the risk from taking one puff on a cigarette or driving a car 0.15 miles on the highway. Many persons do not approach radiation risk rationally. Some tend to ignore the risk because they cannot see any immediate ill effects. Others have an irrational fear of radiation entirely out of proportion to the actual risk (Radiophobia).
End quote.
Note that the straight line model is considered overly conservative. Areas with naturally high background levels do *not* have the number of excess cancers predicted by the straight line model. This leads many researchers to suggest that there is a threshold below which there is no added risk due to radiation.
In fact, a number of such high background areas have a *reduced* cancer risk compared to the general population. This leads some researchers to conclude that small excess radiation exposures may actually be helpful. As the quoted article says, the risk numbers are so low, and confounding factors so many, that it is extremely difficult to make a case either way for this hypothesis.
In any event, what all this means is that the "dead zone" around Chernobyl is today primarily an irrational fear zone instead of an area of actual credible threat.
Gary
Reply to
Gary Coffman
Three major mistakes. 1) no containment structure, 2) a design with a positive void coefficient, ie subject to thermal runaway, and 3) they attempted to operate it completely against established procedures, which in fact caused thermal runaway to occur.
US commercial reactors are designed with 1) effective containment structures, 2) have negative void coefficient, ie damp down if they get too hot, and 3) even when established procedures have been ignored, and 200,000 gallons of coolant was dumped on the containment floor, 1 and 2 have kept off site release to negligible values.
The Soviets designed the RMBK reactors with the implicit idea that no single point critical failures would occur, and that operators would unfailingly follow proper operating procedures.
US commercial reactors are designed with the explicit idea that multiple critical systems can fail, and that operators may take exactly the wrong actions, even over a period of days. Despite that, the reactor must self-damp, and containment must hold. TMI is testimony that even in a worst case scenario loss of cooling and core melt, the design performs as intended.
Note too that current US commercial reactors aren't the best we know how to build. There are *intrinsically safe* designs available which would have avoided even the core melt of TMI.
An intrinsically safe design is defined as one where you can simply walk away from the reactor in any situation, and if operation goes outside well defined parameters, it will gracefully shut itself down due to basic physics principles without need for any active shutdown system.
This sort of reactor was a staple of college nuclear engineering programs when I was in school. They let unsupervised undergrads play with them. As many undergrads might, I've throttled one up to see what she would do. Lots of heat, but no harm no foul as far as safety was concerned, just the friendly blue glow that reminds you Mr Atom is working for you.
Gary
Reply to
Gary Coffman
Well, not exactly. The Windscale fire was a Wigner release gone wrong. It was an air-cooled plutonium breeder reactor. Apparently, for reasons I don't understand, the Wigner release (a procedure that anneals the graphite moderator before the energy stored in the crystal lattice of the graphite becomes unstable) is not needed on water-cooled reactors, possibly due to the different operating temperature of the graphite.
Chernobyl did have a containment structure, although due to the size of these graphite pile reactors, it was impractical to withstand the pressures that are required for our PWR reactors. A massive rupture of the cooling water pipes, with the flashing of tons of water into steam in seconds would likely have burst ANY containment structure. The key is that at the time the bar-betters blew the plant up, it was ready for a fuel replacement, and the fuel in this type of reactor is VERY unstable. Any reduction in the neutron damping of the reactor could cause a wild increase in power output. And, a temperature spike and boiling of the cooling water was enough to raise the reactor to 10 or more times full power output within seconds. They produced the dreaded "superprompt hypercriticality" that is supposed to be practically impossible in our PWR designs.
Oh, the bar bet thing: The operators, without consulting anyone who might have known what could happen, were wondering how long they could keep power in the station only on the inertia of the turbo-alternator. So, they went off grid, and then shut off the steam to the turbine. As the alternator slowed, the power frequency slowed down, and all pumps slowed down. The reactor, just down from full power operation, was still very hot, and they needed full cooling water flow to keep the water from boiling in the pipes. When the water boiled, it kept water from entering the pipes, and the reactor came back to producing nuclear power very quickly, and then went out of control. With the fuel at that advanced state of burn, there was no way to stop the runaway reaction. All control rods were alredy fully inserted.
Jon
Reply to
Jon Elson
Yes, but this is at the center of the asphalt. it was noted to be twice that at the edge of the road, and 5-6 times higher in the weeds.
Note she won't ride with anyone else, because she doesn't want anyone else stirring up dust that she will breathe or get on her.
Jon
Reply to
Jon Elson
I believe the water-cooled graphite-moderated plutonium production reactors at Hanford had to have Wigner releases. I can't put my finger on a cite however.
Reply to
Jim Stewart
With one interesting exception. DOE's N reactor at Hanford, Washington. It was a dual-use reactor, producing plutonium and supplying power to the grid. Water cooled, graphite moderated, *no* containment. The argument can be made that it was a commercial reactor as it's power was sold to the grid.
N reactor was shutdown for safety upgrades in '87 and then put into cold shutdown in '88. It hasn't run since.
Reply to
Jim Stewart
Yeah, but that's still well below what the scientific community considers acceptable exposure. See the article I referenced.
I got the impression that the main reason is just that she likes to ride alone through an area with no people and no traffic. Her main complaint about getting dust on herself and her bike was that the chemical decontamination she'd be forced to endure when leaving the area in that case was hard on the paint of her Kawasaki.
Gary
Reply to
Gary Coffman

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