London, March 3 (ANI): Scientists have found a discarded bottle at a waste site in the US that contains the oldest sample of bomb-grade plutonium made in a nuclear reactor, dating back to 1944.
According to a report by BBC News, the sample dates to 1944 and is a relic from the infancy of the US nuclear weapons programme.
A team from the Pacific Northwest National Laboratory used nuclear forensic techniques to date the sample and track down its origins.
The type of plutonium in the bottle - known as Pu-239 - is a so-called alpha emitter. These alpha particles are too bulky to penetrate skin or paper, but they can cause poisoning if swallowed or inhaled.
It has a half-life (the time it takes for half the radioactive nuclei in a sample to decay) of 24,110 years.
The bottle in question was discovered in a burial trench at the Hanford nuclear site in Washington state, north-western US.
Established as part of the Manhattan Project in 1943, Hanford was home to the world's first full-scale plutonium production facility.
The Manhattan Project was the US' bid to build the world's first nuclear weapon during World War II. The project's roots lay in fears that Nazi Germany was investigating similar technology.
The Hanford site is now the focus of a massive environmental cleanup effort due to high levels of radioactive waste that remain at the site.
While excavating a burial trench in December 2004, clean-up personnel discovered a safe which contained a jug filled with whitish liquid slurry.
Further tests revealed the bottle contained a type of plutonium made by re-processing spent fuel in a manner consistent with early operations at Hanford.
Realising the historic potential of the find, Jon Schwantes and colleagues from the Pacific Northwest National Laboratory carried out further tests on the sample.
In order to determine its age, the researchers analysed the different forms, or isotopes, of plutonium and uranium in the sample.
They found it had been separated from the spent fuel in 1944.
In order to determine which reactor had produced the sample, they compared plutonium isotope ratios from the contents of the bottle against technical data from nuclear research reactors that were operating at the time the sample was made.
Their results strongly suggested the plutonium was manufactured at the prototype X-10 reactor at Oak Ridge in Tennessee, which began operating in 1943, a year after the Manhattan Project was authorised. (ANI)