Small Modular Reactors

By Helen Caldicott

In light of Peter Dutton’s enthusiastic endorsement of the latest nuclear reactors, it is pertinent to review this technology in depth.

There are three types of SMRs which generate less than 300 megawatts of electricity compared with current day 1000 megawatt reactors.

  1. Light water reactors designs – smaller versions of present-day pressurized water reactors using water as the moderator

These SMRs will be expensive because the cost per unit capacity increases with decrease in reactor size. To alleviate costs, it is suggested that safety rules be relaxed, including reducing security requirements and a reduction in the 10 mile emergency planning zone to 1000 feet.

Non-light water designs

  1. High-temperature gas cooled reactors HTGR or pebble bed reactors. Five billion tiny fuel kernels consisting of highly-enriched uranium or plutonium will be encased in tennis-ball-sized graphite spheres which must be made without cracks or imperfections –otherwise they could lead to an accident. A total of 450,000 such spheres will slowly and continuously be released from a fuel silo, passing through the reactor core, and then re-circulated ten times, and cooled by helium gas operating at high very temperatures (900 C).

A reactor complex will consist of four HTGR modules located underground, and run by just two operators in a central control room.

Should temperatures unexpectedly exceed 1600 C the carbon coating will release dangerous radioactive isotopes into the helium gas, and at 2000C the carbon would ignite creating a fierce graphite Chernobyl-type fire.

Although HTGRs produce small amounts of low-level waste they create larger volumes of high-level waste than conventional large reactors.

  1. Liquid metal fast reactors (PRISM)

Fueled by plutonium or highly enriched uranium, and cooled by either liquid sodium, or a lead-bismuth molten coolant. Liquid sodium burns or explodes when exposed to air or water and lead-bismuth is extremely corrosive producing very volatile radioactive elements when irradiated.

Should a crack occur in the reactor complex, liquid sodium escaping would burn or exploding. Without coolant, the plutonium fuel could reach critical mass, triggering a massive nuclear explosion scattering plutonium to the four winds. One millionth of a gram of plutonium induces cancer and it lasts for 500,000 years.

There are two types of fast reactors, a simple plutonium fueled reactor and a “breeder” in which the plutonium reactor core is surrounded by a blanket of uranium 238 which captures neutrons and converts to plutonium.

The plutonium fuel, obtained from spent reactor fuel currently in storage pools at large light water reactors, will be fissioned and converted to shorter lived isotopes – cesium and strontium which last 600 years instead of 500,000. Called “transmutation”, the industry claims that this is an excellent way to get rid of plutonium wastes – fallacious, because only 10% fissions leaving 90% of the plutonium intact.

Fast reactors require a massive infrastructure including a reprocessing plant to dissolve radioactive waste fuel rods in nitric acid, chemically removing the plutonium and a fuel fabrication facility to create new fuel rods. A total of 10,160 kilos of plutonium is required to operate a fuel cycle at a fast reactor and just 2.5 kilos is fuel for a nuclear weapon.

Fast reactors and breeders provide extraordinary long-term medical dangers and the perfect situation for nuclear weapons proliferation.

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