othervise, the guide for a suitabie sample (one-third the guide for the individual) is to be used. This operational technique may be modified to meet special situations. The FRC primary numerical guides, expressed in rem, are provided in two reports, FRC Nos. 1 and 2, surmarized in Table I. guides developed by FRC are expressed in Secondary numerical terms of daily intake of specific radionuclides corresponding to the annual 27G's. Consideration is given to all radionuclides througn all patiways to derive a total annual exposure for comparison with FRC guides. However, for many practical situations a relatively few radionuclides yield the major contribution to total exposure; by comparison, exposures from others are very small. TABLE I v/ FRC RADIATION PROVEC'TVION GUlDEsS— Whole body Gonads Individual Population Group. 0.5 rem/yr 0.17 rem/yr - 5 rems/30 yrs Thyroid 2/ 1.5 rems/yr 0.5 rem/yr Bone marrow 0.5 rem/yr 0.17 rem/yr Bone 1.5 rems/yr 0.5 rem/yr Bone (alternate 2/ guide) 0.003 pg of 2262, in adult 0.001 ye of 7#°Ra in adult skeleton skeleton 1/ 2/ For conditions and qualifications see FRC Report Nos. 1 and 2. Based upona childs thyroid, 2 gms in weight and otherfactors listed in paragraphs 2.10-2.14 of FRC Report No. 2. 3/ Or the biological equivalents of these amounts of 226p., 449-03