Archive for April, 2011

Some nuclear accidents not listed on the scale

April 13, 2011

Keeping Score on Nuclear Accidents –, Matthew Wald 12 April 11, “……. it may be time to review past accidents. Thomas B. Cochran, a physicist at the Natural Resources Defense Council, just did that in preparing to testify on Tuesday afternoon before the Senate Environment and Public Works Committee. (more…)

Plutonium and Mox nuclear fuel

April 11, 2011

Government’s doomed £6bn plan to dispose of nuclear waste,  The Independent, 11 April 11“……Q & A: Why has it come to this?

Q: What is Britain’s “plutonium mountain”?

A: It is the nation’s stockpile of radioactive plutonium, kept as plutonium dioxide powder, packed into special drums stored at Sellafield in Cumbria. A further, smaller amount is stored at the Dounreay nuclear facility in Scotland, the site of the doomed nuclear fast-breeder reactor programme.

Q: Why is the plutonium stockpile so big?

A: This is civilian plutonium, not military. It is largely the result of a decision in the 1960s to extract the plutonium from spent nuclear fuel for use in fast-breeder reactors, which were never built commercially. Britain continued to accumulate civilian plutonium, currently amounting to 84 tonnes, along with foreign-owned plutonium, currently 28 tonnes. The final British-owned plutonium stockpile will be 109 tonnes, once fuel reprocessing from existing nuclear reactors has been completed.

Q: Why do we need to do anything with it?

A: Plutonium remains radioactive for many thousands of years – just how long depends on which isotope. Experts say that doing nothing with the stockpile is not an option – the current methods of storage will eventually become unsafe in decades to come. Plutonium either has to be put into long-term storage, with a view of permanent disposal at some future point in cement or glass blocks, or used in some way that makes it “safer”, such as incorporating it into Mox fuel that is used in a reactor.

Q: Is converting plutonium to Mox fuel safe?

A: Plutonium is an extreme health risk if it gets inside the body – it emits alpha particles which are highly dangerous if they penetrate the skin because they damage the DNA of cells and cause cancer. It is also a security risk because of its use in nuclear weapons and “dirty” bombs. By converting it to Mox fuel, and irradiating this fuel in reactors, some experts believe that plutonium will, ironically, become safer because, being more radioactive, it will be more difficult to handle. Opponents argue that manufacturing Mox necessarily increases security risks not least because of the transport of Mox fuel rods, and even plutonium dioxide, which can be subject to terrorist attacks of accidents.

Q: Is it easy to use Mox fuel in nuclear reactors?

A: Some reactors do use Mox, but only as a small percentage (less than 30 per cent) of the total fuel. The rest of the fuel is conventional uranium oxide. Supporters of Mox suggest that the new generation of nuclear reactors to be built in Britain could burn Mox fuel and thereby be used to diminish the plutonium stockpile. However, the new reactors have been licensed to burn uranium-only fuel and none of the reactor designs being considered has been “just”justified” for Mox, which in any case remains far more expensive than conventional uranium fuel.
Government’s doomed £6bn plan to dispose of nuclear waste – Science, News – The Independent

How the IAEA scores nuclear incidents

April 11, 2011

Eventually, this Japanese incident will be assigned a final numerical rating according to a scale devised by the IAEA.  The scale, called INES (for International Nuclear and Radiological Event Scale), breaks down the severity of nuclear events into bloodless, regimented categories.  Each event ultimately gets a ranking from 1 to 7.

The anomalies, incidents, and accidents of our nuclear world,, 11 April 11 From simple leaks to sudden deaths, Fukushima to Pennsylvania, our world’s brief history of nuclear power is rife with mishaps and tragedy. By Shelley DuBois, reporter

 The nuclear crisis in Japan, the aftermath of an 9.0 magnitude earthquake, including a 7.1 magnitude aftershock yesterday, and a tsunami on March 11, adds to a long list of major nuclear accidents, all of which stem from some combination of human error, insufficient safety procedure, or outdated equipment….

Eventually, this Japanese incident will be assigned a final numerical rating according to a scale devised by the IAEA.  The scale, called INES (for International Nuclear and Radiological Event Scale), breaks down the severity of nuclear events into bloodless, regimented categories.  Each event ultimately gets a ranking from 1 to 7.

A rating of 1 is applied to “an anomaly.” That includes situations in which a person is exposed to a higher level of radiation than the annual limit set by regulators, but does not necessarily develop health problems…..

Level 2 is an “incident” and Level 3 is a “serious incident.”  Which designation applies depends on the extent of security problems, the number of people exposed to radiation, and the dosage they receive.

Levels 4-7 on the INES scale are officially called “accidents” and often, but not always, signal that one or more fatalities from radiation exposure have occurred. The INES ranking scale doesn’t cover deaths at nuclear facilities from non-radioactive chemical leaks or explosions…

level 5, which signifies that there is severe damage to the reactor core and that members of the public will probably be exposed to some level of radiation….

History’s second-most damaging nuclear accident occurred in 1957 at Russia’s Mayak plant in the Kyshtym province.  Caused by the explosion of a tank that contained radioactive waste, this crisis is recorded as a Level 6 “serious accident” on the INES scale. The explosion spewed roughly 75 tons of radioactive waste into the atmosphere, according to the World Nuclear Association, and caused an estimated 200 people to develop fatal cancer.

There has only been one Level 7 “major accident,” and that, of course, was at Chernobyl, located in what is now called Ukraine….
surge of power caused a chain reaction that set the reactor core on fire.  It burned for 10 days and released a cloud of radioactive matter that spread over a wide area of the USSR.

At the plant, 134 emergency workers were exposed to high doses of radiation that killed 28 of them in that same year, 1986.

To that toll of about 30 deaths must be added the indirect effects of Chernobyl—deaths caused, for example, by that radioactive cloud, which is estimated to have exposed more than 5 million people to abnormal doses of radiation.

Radioactive fuel rods

April 9, 2011

Radioactive fuel rods: The silent threat – The Week, 9 April 11,Japan’s nuclear crisis has highlighted the danger of the spent fuel rods piling up outside America’s nuclear plants (more…)