NEUTRON EFFECTS OX ANIMALS 25 



PROTECTION OF PERSONNEL 



The cyclotron was provided with both earth and water shielding, and 

 was located at some distance from the other laboratories. The main water 

 walls were three feet thick and the roof was covered with two feet of water. 

 Depression of the cyclotron room floor level placed the plane of the beam 

 and hence the plane of maximum radiation just below the floor level of the 

 main building. The long duration and high intensity of neutron radiation 

 in this program made it necessary to evaluate all this protection. It was 

 also essential that provisions be made against accidental entry into the 

 radiation area. 



A plan of the cyclotron room, animal house (right) and part of the main 

 building (left) is shown in Fig. 6. The neutron radiation dosage in "n" 

 units for normal daily operation (6 days per week) is shown by the numbers 

 in the area where measurements were made. This dosage was exceeded 

 during the last year of the program but did not average double the earlier 

 dosage. Thus doubling the dosage values given in the diagram gives the 

 maximum average daily dosages at any of the points. 



The point .-1 represents the point of closest approach to the radiation 

 area by cyclotron operators during normal operation. C is the limit of 

 permitted approach during radiation. B is the limit of approach permitted 

 in the animal house. Illuminated warning signs at C and D automatically 

 went on during cyclotron operation. An additional safety device was a 

 photoelectric cell installed at D Avhich operated a bell signal in the control 

 room so that the operator could stop irradiation if the cyclotron room was 

 inadvertently entered from the animal house. 



^Yith reasonable care by the cyclotron operators it was thus impossible 

 for anyone connected with the radiation program to receive an accumu- 

 lative dosage of more than .001 n per day. Actual dosages received by 

 personnel were probably a fraction of this. Blood examinations were made 

 periodically upon all operators and attendants who might be exposed to 

 radiations. 



Additional radiation monitoring was achieved by film badges worn by 

 personnel throughout the program. These consisted of dental films set in 

 brass frames. A portion of the film was covered with a cadmium shield to 

 absorb neutrons, this area being used to monitor gamma radiation only. 

 These badges were checked weekly and made possible detection of any 

 accidental entry into the radiation area. During the program there was 

 no evidence of any badge being exposed to detectable amounts of radiation 

 while worn by personnel. 



REFERENCES 



(1) Aebersold, p. C. and Anslow, G. A., Phys. Rev., 69, 1, 1946. 



(2) Staub, H., axd STEPHEN'S, W. E., Phijs. Rev., 55, 131. 1939. 



(3) Aebersold, P. C, axd Lawrexce, J. H., "Annual Review of Physiology", 



Stanford University, 4, 25, 1942. 



