Scintillation units for gamma-radiation detection are described. The u
nits are built around CsI(Na) single crystals (250-350 mm thick and 54
mm in diameter) and FEU-151 or Urengoi-2 photomultipliers. In spectro
metric mode of operation the units can work at temperatures from -60 t
o +250-degrees-C continuously, and at 280-degrees-C for up to 3 h.