PRINCIPLES OF NAVAL ENGINEERING 



measure gamma radiation alone or tiiey can 

 measure combined gamma radiation and beta 

 radiation; an indirect measure of beta radiation 

 can be obtained by subtracting the gamma radia- 

 tion from the gamma-beta radiation. 



ALPHA SURVEY METERS.-Meters for 

 measuring alpha radiation are usually calibrated 

 to give a meter reading in counts per minute 

 (c/m, or cpm). However, some alpha survey 

 meters give a reading in a unit called disinte- 

 grations per minute (d/m). The two units are 

 not the same numerically. 



DOSIMETERS. -There are two basic types 

 of dosimeters. Self- reading dosimeters can be 

 read by the person wearing the instrument. 

 Nonself- reading dosimeters cannot be read 

 directly by the wearer but must be read with the 

 aid of special instruments. Some dosimeters 

 are calibrated in roentgens, others in milli- 

 roentgens. Both self- reading and nonself- read- 

 ing dosimeters measure exposure to radiation 

 over a period of time— in other words, they 

 measure accumulated radiation exposure. 



Self- reading dosimeters are provided in 

 various ranges for use by personnel aboard ship. 

 Some of these self-reading dosimeters indicate 

 accumulated gamma radiation from to200mr; 

 others indicate doses from to 100 r; others 

 from to 200 r; and still others from to 600 r. 

 The dosimeter selected for any particular use 

 will depend on the radiological situation existing 

 at the time. Self-reading dosimeters must be 

 charged before they are used. A special charging 

 unit is furnished for shipboard use. 



High-range nonself- reading dosimeters of 

 the DT-60/PD type are furnished for use aboard 

 ship. A dosimeter of this type consists of a 

 special phosphor glass between lead filters, 

 encased in a bakelite housing. The dosimeter, 

 which is small, lightweight, and rugged, is worn 

 on a chain around the neck. This dosimeter will 

 measure accumulated doses of gamma radiation 

 from 25 r to 600 r. A special instrument, the 

 CP-95/PD computer- indicator, is required to 

 read the DT-60/PD dosimeter. 



Film badge dosimeters are nonself- reading 

 devices for measuring both gamma radiation 

 and beta radiation in low or moderate ranges. 

 A film badge uses a special photographic film 

 which is surrounded with moisture-proof and 

 light-proof paper and shielded with lead, cad- 

 mium, plastic, or other shielding material. By 

 the use of different shielding materials, the badge 



can be made to differentiate between gamma 

 radiation and beta radiation. Laboratory tech- 

 niques are required for the development and 

 reading of the film. 



Detection of Biological Agents 



Basically, there are two possible approaches 

 to the problem of detecting biological agents. 

 Physical detection is based on the measurement 

 of particles within a specified size range (and 

 possibly the simultaneous measurement of other 

 physical properties of the particles). Research 

 is currently being done with a view to develop- 

 ing effective methods of physical detection. 

 Biological detection involves growing the or- 

 ganisms, examining them under a microscope, 

 and subjecting them to a variety of biochemical 

 and biological tests. Although positive identifi- 

 cation can frequently be made by biological 

 detection methods, the procedure is difficult, 

 exacting, and relatively slow. By the time a 

 biological agent has been detected and identified 

 in this fashion, personnel may well be showing 

 symptoms of illness. 



Biological detection may be divided into two 

 phases: the sampling phase and the laboratory 

 phase. The sampling phase may be a joint re- 

 sponsibility of damage control personnel and of 

 the medical department. The laboratory phase 

 is obviously a medical department responsibil- 

 ity. 



Detection of Chemical Agents 



Various detection devices have been devel- 

 oped for the detection and identification of 

 chemical agents. Most of these devices indicate 

 the presence of chemical agents by color changes 

 which are chemically produced. To date, no 

 single detector has been developed which is 

 effective under all conditions for all chemical 

 agents. A number of devices, including air 

 sampling kits, papers, crayons, silica gel tubes, 

 and indicator solutions, are in naval use. Some 

 of these devices are also useful in establishing 

 the completeness of decontamination and in es- 

 timating the hazards of operating in contami- 

 nated areas. 



MONITORING AND SURVEYING 



The monitoring and surveying of any area 

 contaminated with NBC contamination is a vital 

 part of NBC defense. In general, monitoring 



76 



