is provided with a substantial thickness of a thermal insulator 20 formed from calcium silicate this layer is provided in a series of sections see fig2 the materials provision in solid sections ensures accurate positioning during assembly and use a single base layer of insulator 22 and four wall sections 24 line the container itself when the container is loaded as described below a two piece insulating top layer is applied these two pieces 26 28 are shaped to interconnect with one another the rectangular box defined by the interior surfaces of the insulating layers receives an internal container 30 a having four walls and a base and also made of boronated steel or stainless steel this container 30 a is also provided with a lid 31 as shown in fig1 as seen in fig3 the container consists of a series of interlocking vertical walls 30 made of boronated steel stainless steel the container 30 a has two pairs of internal walls 30 at 90 degrees to one another defining nine chambers 32 within the pail load in use within each of the eight peripheral chambers a fuel drum or pail 36 is received the central chamber 32 a is provided with a polythene neutron absorber 38 the absorber 38 is itself provided.