  The paper describes methods and presents results of the Troitsk Nu-mass
experiment spectrometer cleanup, which inner volume (40 m3) and surfaces (160
m2) was contaminated by 4.4 GBq of tritium. The Troitsk Nu-mass experiment of
Institute for Nuclear Research of Russian Academy of Sciences, Moscow, is
designed to measure the spectrum of electrons from tritium decays in order to
search for hypothetical particles - sterile neutrinos. As a result of equipment
failure, the spectrometer internal volume was contaminated with tritium. The
contamination made measurements impossible and the research program stopped.
The methods of vacuum extraction, hydrogen soaks, and water vapour soaks were
used for cleanup. As a result of detritiation, the background level of the main
detector of the Troitsk Nu-mass spectrometer decreased by more than 10 times,
which made it possible to resume work. The results are consistent with the data
obtained earlier for volumes in normal conditions in the air and can be used
for planning work on detritiation of similar installations.
