The burns are caused by direct exposure to beta rays
, the utility added.
Strontium-90, materials that emit beta rays
and causes bone cancer, likewise hit 1.
Tepco said the level of those that emit beta rays
was 230 million becquerels per liter.
About 10 tons of water may have leaked, the utility said, noting the pipe contained some 37 million becquerels per liter of radioactive substances that emit beta rays
such as strontium-90 in a reading in August, against the legal limit of 30 becquerels for strontium-90.
Tepco said the radiation measured was beta rays
, which would be easier to protect against than gamma rays.
Alpha rays carry a positive charge, beta rays
carry a negative charge and gamma rays are neutral.
can release radioactive gamma and beta rays
that can cause cancer.
Tritium, a hydrogen isotope in gas form that emits radiation in the form of beta rays
, has long been the subject of scrutiny by government and retail groups.