A radiation treatment unit having an elongated shape and a central longitudinal axis comprising: (a) a first pipe assembly comprising: a first coiled pipe for passing therethrough a fluid to be treated and having a first coil inner cylindrical surface defining a first cylindrical cavity a first radiation source disposed within the first cylindrical cavity and a first support assembly supporting at least said first coiled pipe, and (b) a second pipe assembly comprising: a second coiled pipe for passing therethrough a fluid to be treated and having a second coil inner cylindrical surface defining a second cylindrical cavity, a second radiation source disposed within the second cylindrical cavity and a second support assembly supporting at least said second coiled pipe said second pipe assembly being configured to be coaxially inserted within said first cylindrical cavity so that the second coiled pipe is disposed between said first radiation source and said second radiation source, so that a fluid passing through the first coiled pipe is exposed to an inside radiation of the first radiation source and a fluid passing through the second coiled pipe is exposed to an outside radiation from the first radiation source and an inside radiation from the second radiation source.Linvention concerne une unité de traitement par rayonnement ayant une forme allongée et un axe longitudinal central comprenant : (a) un premier ensemble de conduits comprenant : un premier conduit hélicoïdal dans lequel circule un fluide à traiter et dont la surface cylindrique interne définit une première cavité cylindrique une première source de rayonnement située à lintérieur de la première cavité cylindrique et un premier ensemble-support sur lequel repose au moins ledit premier conduit hélicoïdal, et (b) un second ensemble de conduits comprenant : un second conduit hélicoïdal dans lequel circule un fluide à traiter et dont la surface cylindrique interne définit une seconde cavité cylindrique une
