Tritium hazard rating 'should be doubled'
来源：未知 作者：毕旮 时间：2019-03-02 06:17:04
By Rob Edwards Radioactive tritium, commonly discharged in large amounts by civil and military nuclear plants around the world, may be more dangerous than previously thought. The cancer risk for people exposed to tritium could be twice as high as previously assumed, an expert report for the UK government’s Health Protection Agency (HPA) concludes. The report suggests that international safety standards need to be tightened up, which will put pressure on nuclear plants to cut their emissions. Mark Little, one of the report’s authors from Imperial College in London stresses that the risks are still low, even amongst nuclear workers with the highest exposures. But evidence that tritium causes more biological damage than assumed is “solid enough” to justify a change, he says. Tritium – a radioactive isotope of hydrogen with a half-life of 12.3 years – is an essential component of the H-bomb and a waste product of the nuclear power industry. It is also widely used in medicine, and would help fuel future nuclear fusion reactors, if they ever become viable. Since the 1950s, vast quantities of tritium have been released into the environment from numerous nuclear plants, including Savannah River in the US, Sellafield in the UK, Marcoule in France, and Ontario Power Generation in Canada. Workers are known to have been exposed at other facilities, including Aldermaston in England and Mayak in Russia. But the 100-page report from the HPA’s Advisory Group on Ionising Radiation, argues that the weighting factor used by the International Commission on Radiological Protection (ICRP) in Stockholm, Sweden, to assess risks should be increased from one to two. This means that the maximum acceptable radiation doses worldwide would have to be recalculated. “Tritium is not highly radioactive, but it can become widely dispersed in the environment, and we felt a special review of the evidence was necessary,” says the advisory group’s chairman, Bryn Bridges. The health risks of tritium were investigated in response to a recommendation in 2004 from the UK government’s former Committee Examining Radiation Risks of Internal Emitters (CERRIE). According to one of the committee’s members, nuclear consultant, Pete Roche, the weighting factor for tritium was lowered in 1969 because of pressure from the US military. “There have been calls for it to be increased ever since,” he says. “In the meantime the industry can no longer assume it will be allowed to release large quantities of tritium.” The Nuclear Decommissioning Authority, which is responsible for many of the tritium-emitting plants in the UK, promises to “consider carefully the impact of any agreed increase in radiation weighting.” The ICRP’s scientific secretary, Jack Valentin, says: “We will look at this, and we will be considering it.” The Nuclear Age – Learn more about all things nuclear in our explosive special report. Cancer – Learn more about one of the world’s biggest killers in our comprehensive special report. More on these topics: