Tritium is a radioactive isotope of hydrogen that occurs naturally in the environment and is a common by-product of nuclear plant operations. It emits a weak form of beta radiation that does not travel very far and cannot penetrate human skin, according to the NRC. A person who drank water from a spill would get only a low dose, the NRC says.
The NRC says tritium spills happen from time to time at nuclear plants, but that it has repeatedly determined that they've either remained limited to the plant property or involved such low offsite levels that they didn't affect public health or safety. Xcel reported a small tritium leak at Monticello in 2009.
