ACTIVITY LKVELS IN LABORATORY DESIGN AND PRACTICE 



case of a ciiiitlris. He points out lliat, clue to tlic cxtcinal radiation hazard 

 associated with ^ contamination, no relaxation of the '•"'Sr Hmit can be 

 allowed in applying it to other ^ emitters. In the case of a radiation, how- 

 ever, since the hazard is entirely one of ingestion and inhalation, some 

 relaxation can be allowed in considering less radio-toxic a emitters than 

 23'*Pu and --^Ra. In the calculations of this paper Dunster's figure of 

 4x 10"'* [xC/cm- for widespread j3 contamination has been applied to all 

 j8 emitters and his figure of 10"^ [xC/cm^ for -^s^Pu and ^seRa contamination 

 has been modified for other a emitters in the ratio of the respective maximum 

 permissible daily intakes. The total amounts of the various nucleides which 

 may be distributed around the laboratory over a number of years, without 

 exceeding the allowable contamination level, have then been calculated 

 from these figures. The amount of activity which may be handled in the 

 laboratory can then be obtained by integrating an assumed daily fractional 

 spread, witli due allowance for radio-active decay. 



DISCUSSION OF RESULTS 



Table 1 sets out the assumptions which have been used to relate the recom- 

 m'rnded maximum amounts of activity for use under specified conditions to 

 the various hazards discussed as in the last section of this paper. The 

 calculations have been carried out for a number of nucleides and tlic final 

 generalized expressions given in the Table 2 have been chosen to limit the 



Table 2. Recommended maximum amounts of activity for use under specified 



conditions 



White Area Operations involving radio-active material in any physical form: 



— up to 10 [xC of any /3y emitter except ^"Sr and --''Ra which should be limited 

 to 1 (xC. 



— up to 10-1 |j^Q of any a emitter except 232-^};, ^^j natural U of which amounts 

 up to 6 X 10~i [iC shall be permitted.* 



Blue Area Operations involving radio-active material in a dry dusty form: 

 Open room — 10^ X m.p.d.i.f 

 Fume hood — 10* X m.p.d.i. 



Red Area Operations involving radio-active material in a dry dusty form : 

 Open room — 10* > m.p.d.i. 

 Fume hood — 10" :■. m.p.d.i. 



All quantities above 10* X m.p.d.i. should be handled in a glove box or sealed 

 cell. 



Aiodifying Factors 

 All Areas 

 Storage in closed but suitably vented containers — increase limits by a factor of 10'. 



White Areas 



(In the case of 232-^]^ ^y^^ natural U only) 



General dry but non-dusty operation — increase by a factor of 10. 



Wet chemistry — increase by a factor of 10-. 



Blue and Red Areas 



General dry but non-dusty operations — increase by a factor of 10. 



Wet chemistry or more general operations on materials of low specific activity — increase by 



a factor of 10-. 



* A special limit is allowed for -'^Th and natural U duo to their low specific activity. 



t The maximum permissible daily intake is to be taken here as the daily water intake x I.C.R.P. occupational 

 permissible drinking water concentration or the daily air intake X I.C.R.P. occupational permissible air concen- 

 tration, whichever is the smaller. 



150 



