280 Applied Biophysics 



The films which are issued to radium workers are half cov- 

 ered with sheet lead 1 millimeter thick, which absorbs any beta 

 radiation. The shielded half of the film thus records the gamma- 

 ray dose, whereas the unshielded portion records both beta and 

 gamma radiation. In the case of luminizers, it has been found 

 that there is a large beta-ray effect, and subsequent inspections 

 of many of the departments have revealed that most of the dose 

 is due to contaminated benches and clothing. In the major- 

 ity of cases, the total doses are now well below the tolerance 

 level. 



It seems possible to use the film technique for the measure- 

 ment of neutrons which fall on the body. Fast neutrons would 

 be slowed down in the tissue and would "evaporate" from the 

 surface of the body with thermal velocities. If the film is covered 

 with a thin foil of, say, cadmium, rhodium, or indium, which 

 have a high-capture cross section, these elements would capture 

 the neutrons, becoming radioactive and emitting ionization radia- 

 tions which would blacken the film. The radioactivity should, 

 preferably, be short-lived, so that there w^ould be no need to 

 take into account the lapse of time between the initial irradiation 

 of the film and the photographic development. 



The inspections of luminizing departments also include tests 

 of the radon concentration of the air of the workrooms, and 

 tests of the radium in the bodies of luminizers, part of the radium 

 being assessed by means of the alpha rays from the radon con- 

 tained in the exhaled air and part by means of the gamma rays 

 from the subsequent disintegration products of the radon trapped 



in the body. Similar tests have been carried out by Jones and 

 Day.i2 



It will be apparent from the foregoing review that, while there 

 is much to be learned about the tolerance doses for various types 

 of ionizing radiation, and while there is an ever-growing number 

 of radiological workers using an ever-widening range of man- 

 made radiations, sufficient experience has already been gained 

 to be able to tackle the new protection problems with high hopes 

 of evolving effective safety measures, 



