thickness as long as the cavity is either sufficiently small or if the filling 1s of the same gros2 atomic composition as the wall material itself, We use three types of ionization chamberg in our survey, The firet is the Failla-Rossi Tissue Equivelent Chamber, the secong is a Graphite Well Carbon Dioxide Filled Ionization Chamber and the third is a Polyethylene Moderator Steel Wall BF Filled Ionization Chamber. A Tissue Equivalent Chamber is composed with a wall and filling of the same gross atomic compogition as average wet tissue. This meane that 1t measures the tissue dose rate at a depth of 3/5ths of a centimeter, It has one disadvantage due to the currently accepted RV of 10 for fast neutrons. Equal ram dose rates of radiation of different types do not produce equal fone ization currents, Seven and a half millirem per hour of fast neutron radiation produces only one tenth the lonization current due to seven and a half millirem per hour of