ACTINITY LF.VELS IN LABORATORY DESIGN AND PRACTICE 



Energy Coininission. It is therefore perhaps relevant to first descrilic the 

 situation existing at that Estal)lishment. All of the laboratories in the radio- 

 chemical building fall w ithiii the classification (I) of Dunster, being provided 

 with readily decontaminable surfaces, adequate fume hoods and forced 

 ventilation giving approximately 20 room changes an hour. Following 

 British practice, areas within the radio-chemical building are classified as 

 red, blue or white. A red contamination area is one in which the normal 

 procedures in the area may sometimes give rise to hazardous levels of 

 contamination of surfaces and of breathing air. A blue contamination area 

 is one in which contamination is unlikely to reach hazardous levels, and a 

 white area one in which the amounts of activity in use are not such as to 

 necessitate any special restrictions. The blue and red contamination areas 

 are located in the active section of the building and access to them is by way 

 of a change room. Measures against the spread of contamination in these 

 latter areas include regular monitoring of all laboratory surfaces, systematic 

 cleaning procedures, clothing and shoe changes for persons entering and 

 leaving the area, showering, prohibition of smoking and eating, and the 

 monitoring of hands for contamination. In general, stricter measures apply 

 in red areas than in blue. A decision on the necessity for contamination 

 control measures then, amounts to deciding the maximum amounts of 

 radio-activity which should be used in a white area. No consideration has 

 been given here to the y radiation hazard associated with the radio-active 

 material to be used in the laboratory, it being assumed that adequate 

 shielding will be piovided to reduce the y radiation dose rate to acceptable 

 levels. 



ROUTES OF INGESTION AND INHALATION 



Three possible sets of circumstances leading to the ultimate ingestion or 

 inhalation of radio-active material have been considered in these calculations, 



viz. '• — 



[a) The day-to-day transfer of small amounts of radio-active material into the body 



Under this heading, has been considered the direct transfer of radio-active 

 material into the body, either by ingestion or inhalation, resulting at the 

 time of handling material, as distinct from transfer by contamination build- 

 up. The daily ingestion and inhalation by this route must be limited to the 

 maximum permissible daily intakes of the particular nucleide (m.p.d.i.) 

 derived directly from the maximuin permissible drinking water and air 

 concentration figures which were suggested by the International Commission 

 on Radiological Protection (I.C.R.P.). 



{b) A single accidental inhalation or ingestion of an appreciable fraction of the 

 material being handled 



For the purposes of these calculations, the maximum amount of radio- 

 active material, which it is considered may be tolerated as a single ingestion 

 occurring only once in a lifetime, has been put equal to the amount which 

 would produce an integrated dose to the critical organ of not more than 

 25 REM over a lifetime, except in the case of '-^apu and '-^-Th. In these 

 latter cases the long effective half-lives result in the dose being delivered at a 



148 



