The Reactor — Getting Heat by Splitting

Not burning — splitting

Wood burning is the outer parts of atoms trading places with oxygen. The nucleus at the centre is held together far more tightly.

Undo that binding and what comes out is about a million times larger for the same weight. That is the gap between the truckloads and the pellet.

Once started, it continues itself

Certain uranium nuclei split in two when a neutron strikes them. Heat comes out — and so does something else: two or three more neutrons.

Those strike neighbouring nuclei and split them, releasing more neutrons again. One becomes two, two become four, and it spreads.

Note the mirror image of fusion. Fusion goes out at the slightest disturbance, so the difficulty is holding it. Fission continues on its own, so the difficulty is holding it down.

A research reactor is not a power station

The reactor in Daejeon does not make electricity. It is a research reactor named HANARO.

A power reactor, incidentally, is in the end boiling water. Why every power station boils water, and why the solar cell alone does not, is set out in the article on solar cells and hydrogen.

Research reactors are run for neutrons rather than heat. Neutrons carry no charge and so travel deep into matter — useful for seeing cracks inside a component that looks sound, or working out how a material is arranged. Radioactive medicines used in hospitals are made here too.

A little further in

Why building and watching are kept apart

Here is what really distinguishes this technology. Daejeon holds not one nuclear organisation but three.

1. The builder — the Korea Atomic Energy Research Institute, which develops reactors and related technology.
2. The watcher — the Korea Institute of Nuclear Safety, which inspects and regulates operating plants.
3. The counter — the Korea Institute of Nuclear Nonproliferation and Control, which accounts for every gram of nuclear material.

The counting may sound strange. Materials like uranium can also make weapons, so every country declares what it holds to an international body and has it verified. What came in, what went out, what remains — a continuous reckoning. It is closer to bookkeeping than to physics.

On being afraid of radiation

Radiation is what a nucleus gives off settling into a steadier state. It cannot be seen or smelled, so no sense of ours catches it — which is part of why it frightens us more than other hazards.

But what our senses miss, instruments catch very well. Radiation is among the easiest dangers in the world to measure, down to tiny amounts. That handling a danger begins with measuring it ties this back to the article on standards.

What you would study to do this

Nuclear work is not one discipline either.

1. Someone who calculates where the neutrons go — nuclear engineering.
2. Someone who handles hot water and steam — thermal and fluid mechanical engineering.
3. Someone who finds materials that survive radiation — materials engineering.
4. Someone who measures and manages the dose people receive — radiation protection.
5. Someone who works out in advance what happens when things go wrong — safety analysis.

That last line is the character of the field. More people are employed calculating the failure than the ordinary running.

The question that remainsIf safety requires that the maker cannot inspect its own work — what around us is still inspected by the people who made it?