Reply #27: The Candu Reactor

[NNadir]

The Candu Reactor was originally developed by the Canadians to use unenriched (natural) Uranium. The reason for taking this approach was that the Canadians did not want to invest in (then) extremely expensive Uranium isotopic separation plants, and recognized that it was much easier to separate hydrogen isotopes. The name CANDU derives from fusing the words Canadian and Deuterium.

The main principle behind the reactor is that it uses deuterium oxide (heavy water) as a moderator as opposed to the natural water used in most Pressurized Water Reactors (PWR) and boiling water reactors (BWR). Deuterium has an extremely low neutron capture cross section, which is a measure of the probability that a nucleus will absorb a neutron. It also has a very large potential for slowing neutrons down to ordinary molecular speeds, a process generally called "thermalizing" neutrons. Combined these two properties result in a reactor that has a very high "neutron efficiency," meaning the neutrons are available for doing work.

The cost of enriched Uranium has fallen a great deal, especially now with the important task (probably to be abandoned by the awful Bushies) of fissioning surplus weapons grade material. Thus the chief motivation for building the CANDU, at least from a financial perspective has been negated.

It turns out that the CANDU reactor is extremely useful for two other reasons. One reason is that it is possible to use it as a plutonium burner. The other is that using U-233 as a fuel (derived from Thorium) the reactor can function essentially as a thermal breeder reactor, which actually creates more fuel than it burns. (The most widely explored breeder reactors are "fast reactors" cooled with liquid metals.) As a practical matter, this is expressed by the ability of these types of reactors to achieve high "burn-ups" (total energy obtained per unit mass of fuel), conditions that greatly reduces the volume of "waste" that needs processing.

Candu reactors also have an important advantage in that it is possible to continuously refuel them. This latter property eliminated the down-time that reactors require to be re-fueled. Such down-time has important consequences in nuclear economics. In an earlier era, when reactor operators were relatively inexperienced, excessive downtime had a great negative impact on the economics of nuclear power. The reason that the US nuclear industry has been able to increase it's capacity to the highest in its history (by almost 20%) without building a single new reactor (and while actually closing several) is precisely this: great reductions in down time, especially in refueling operations. The CANDU reactor completely eliminates this economic problem almost completely.

There is a drawback to continuous fueling capability: It can under certain circumstances allow for the use of a reactor for the production of weapons grade material, especially when pure Uranium is used as a fuel. Therefore CANDUs have impacts on the area that, in my opinion, represents the most serious objection to nuclear power, proliferation risk. In the CANDU case, this is somewhat offset by the fact that the CANDU is a perfect reactor for destroying and/or denaturing plutonium and recovering energy in the process. The Clinton-Gore administration had quietly sounded out the Canadians on using Candus precisely for this critical (pun intended) disarmament task. Indeed, where the reactor is fueled with Plutonium and Thorium it has tremendous non-proliferation value, as the use of U-233 in weapons is extremely problematic. Thus the CANDU reactor can be a tool for peace or a tool for war, depending on who is using it. CANDU reactors should be subject to close international scrutiny. The Canadians have used them well; and Canada is a nation that is demonstrably more civilized than the United States, for instance. This is an instance where a technological development is ethically and morally neutral: It can be used for either great good or great harm, depending on the ethics and morality of the group using them.

The Indians have basically appropriated the CANDU design and have built copies of this type of reactor. There is an economic purpose for doing so: India has much larger reserves of Thorium than it has Uranium. However, it is worth noting that the Indians are egregious violators of non-proliferation agreements. They, with the Pakastanis stand closer than any other nation to the precipice of potential nuclear war. I don't trust the Indians with CANDUs. I do note however that they are excellent nuclear engineers, and have published good work on the non-weapons use of CANDU reactors.

I really don't know how much presence the Halliburton Corporation has in the nuclear industry. There is none of which I am aware, but I admit to not being aware of many of Halliburton's filthy dealings and operations. It is true that the left has been generally hostile to nuclear power, something I am trying, with mixed success, to reverse. This historical anti-nuclear attitude of the left has probably caused many of the people in the nuclear industry to develop political attitudes that lean rightward. People who are aware of my politically liberal leanings are often surprised by support for nuclear power, an attitude that actually represents a reversal of my previous views on the subject.

In any case, the Canadians, the Japanese, the Germans and the French all have extensive and successful nuclear power programs. None are beholden to Halliburton; arguably these states hold Halliburton in contempt, much as you and I do. The Japanese, Canadians and the Germans have been model states in their use of nuclear technology. Although the technical capability to develop nuclear weapons is a trivial barrier in those nations, none of these three has ever seriously considered becoming nuclear armed states.

I don't believe that hostility to nuclear energy is consistent with realistic environmentalism. It is unfortunately not possible to produce energy with a zero environmental, economic, and moral risk. The best we can hope for is yo minimize these risks. I argue that nuclear energy is the maximally minimized risk strategy available to humanity in the early 21st century. If it happens that people on the right hold similar views on promoting nuclear energy to those which I, on the left, also hold, it has little bearing on the desirability of such views. People often undertake identical actions for widely varying, even opposing, reasons. If it is true that Halliburton supports nuclear energy for the purpose of giving themselves another avenue to pillage and plunder, and I support nuclear power because I am a concerned environmentalist (and Greehouse gas nut-job), the end, if not the means, is the same.