Three infrared lasers are focused on a cell filled with caesium
Contrary to expectation, it happened that the hydrogen maser, though potentially slightly superior to the caesium
beam frequency standard, progressed only slowly (one of its uncertainties comes from the wall shift), and that caesium
standards were so much improved that an almost perfect confidence was acquired in their reliability, within the most severe present needs of precision.
Although different elements have since been used in other clocks, the caesium
clock has remained the standard of time and frequency.
In March 2013, TEPCO, the Japanese utility that operates the tsunami-damaged nuclear power plant, said it detected a record 740,000 becquerels per kilogram of radioactive caesium
in a fish caught close to the plant, which was 7,400 times the government limit for safe human consumption.
Current detection methods can only localise contamination on a scale of metres to kilometres, and they do not specifically identify caesium
. Researchers in Japan, led by Katsuhiko Ariga at the National Institute for Materials Science, have now developed a way to detect caesium
contamination on a scale of millimetres.
The 11 cows all showed high levels of radioactive caesium
, ranging from 1,530 to 3,200 becquerels per kilogram, compared with the legal limit of 500 becquerels, the Tokyo statement said.
After being used inside a patient's body the caesium
rod was thought to have been returned to a locked store.
The Bulgarian Atomic Agency yesterday admitted two cylinders of highly radioactive caesium
137 had been stolen from the Kremikovci smelting plant, just outside the capital Sofia.
Dounreay, , which is being decommissioned, is heavily contaminated with caesium
and other heavy metals.
Caesium-137 accumulation or loss at each sampling point can be determined by subtracting the average caesium
areal activity at the reference site from the areal activity at each sampling point following the method of Sutherland and de Jong (1990).