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Nuclear: Freedom from concern

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Yes, these reactors can give us freedom from want. Nuclear reactors are, sensibly designed, inherently safe. One should not place them over known faults in the earth; or upwind of a major metropolis. One should not fear them nearly so much as one might fear the spend thrift politicians shoving us toward economic disaster with its associated evils, e.g., hunger and despair. Of course the average light bulb in the NY subway once lasted 50 years; now fails in less than a month. GE, the company responsible for the reactor, made the latter bulb and the reactor.

One pound of Uranium can produce 1 megawatt of power for about one year; one pound of oil is good to fry with.

Two Reactor Types

There are many types; only two are shown below …

A heterogeneous reactor is one with control rods of graphite and safety rods of, typically, boron steel or cadmium; the homogeneous reactor (such as the Fuchisima reactor) is one using natural water as a moderator.

The difference is that in the (not quite so efficient) former reactor the controlled fission is moderated by a system that inserts the rods mechanically into the core, thus quenching the chain reaction and production of neutrons, which in turn sustain the reaction.

In the latter reactor the nuclear fuel is a soluble salt of Uranium 235-enriched dissolved in water acting as a dispersed moderator, in a vessel or tank which is a neutron reflecting shield of beryllium oxide. Into this solution is inserted cadmium rods to control the reproduction factor and the overall temperature is maintained at the desired level through use of spiral metal tubes containing cooling water.

Sometimes the fuel elements are in the form of plates containing a very high proportion of Uranium 235 in Uranium 238 alloyed with aluminum. Depending on the design these reactors can become “breeder reactors” (not possible with heterogeneous reactors). It is suspected that the Fuchisima reactor is of this type (converting U238 into fissile material Plutonium 239). I have no way of knowing this.

In any event the parent – daughter reactions result in product nuclei (fissile fragments), which have excess neutrons which they release, or which are converted into protons by negative beta particle emission (beta rays). These products, or so-called daughter nuclei,

(or what I call secondary fissile fragments) then decay successively through beta particle emission until a stable nuclide is reached.

Contamination

In general gamma rays are emitted by the parent nuclei which decay then by emitting beta rays. Hence we have radiation of gamma, beta, and neutron flux to consider in the contaminated zone as well as fissile fragments which can be ingested or absorbed by the body. N.b., recall what Piet Hein once said: “what doesn’t kill you outright, makes you stronger.” hein made up “grooks” or poems to relay intelligence during the Nazi occupation of Denmark during WWII. This was one. For one who has survived a number of nuclear incidents I can affirm his conclusion.

Fission products; yield in percent

The predominant radioactive fission products include isotopes of iodine, cesium, strontium, xenon and barium. A few examples follow:

I 131 decays with a half life of 8.0 days with Beta and Gamma emissions. This nuclide upon decaying transforms into Xe 131

Cesium 137 with a half life of 30 years decays by Beta emission into a metastableomer of Barium 137

Strontium 90 undergoes Beta decay to Yittrium (Y) which in turn undergoes Beta decay into Zirconium (Zr 90) which is stable. Sr 90 has a half life of about 29 years and so is very long-lived. It is chemically a direct replacement for calciou so it replaces normal calcium in bones and teeth. (The cows eat the grass that contains the fragments and we then partake of the milk). It is the most dangerous of all from this standpoint. To put this into perspective however the nuclear tests in the 1950s produced more Sr 90 than any 500 reactors could produce. We lived through the 1950s, indeed some of us even lived through the 1930s. The 50s didn’t seem to hurt us that much. The 30s hurt much worse. Be calm.

Fragments, with the percent of occurrence from fission are as follows:

CS 135             6.9

CS 137            6.4

Tc   99             6.1

Zr   93             5.5

Sr   90           4.5

Kr  92             2.2        (remember Kryptonite – fictional Superman stuff)

Plus

Sn 126

Pd 107

And other smaller amounts

E.g., the decay chain for Kr,

Kr -> Rb-> Sr-> Y -> Zr -> Cb -> Mo

Each in the chain is radioactive except the last. Although it all sounds scary in reality it is

far less onerous than some of the foods we eat every day. It’s all relative.

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Nelson Propane

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