Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGmeasure gamma radiation alone or tiiey canmeasure combined gamma radiation and betaradiation; an indirect measure of beta radiationcan be obtained by subtracting the gamma radiationfrom the gamma-beta radiation.ALPHA SURVEY METERS.-Meters formeasuring alpha radiation are usually calibratedto give a meter reading in counts per minute(c/m, or cpm). However, some alpha surveymeters give a reading in a unit called disintegrationsper minute (d/m). The two units arenot the same numerically.DOSIMETERS. -There are two basic typesof dosimeters. Self- reading dosimeters can beread by the person wearing the instrument.Nonself- reading dosimeters cannot be readdirectly by the wearer but must be read with theaid of special instruments. Some dosimetersare calibrated in roentgens, others in milliroentgens.Both self- reading and nonself- readingdosimeters measure exposure to radiationover a period of time— in other words, theymeasure accumulated radiation exposure.Self- reading dosimeters are provided invarious ranges for use by personnel aboard ship.Some of these self-reading dosimeters indicateaccumulated gamma radiation from to200mr;others indicate doses from to 100 r; othersfrom to 200 r; and still others from to 600 r.The dosimeter selected for any particular usewill depend on the radiological situation existingat the time. Self-reading dosimeters must becharged before they are used. A special chargingunit is furnished for shipboard use.High-range nonself- reading dosimeters ofthe DT-60/PD type are furnished for use aboardship. A dosimeter of this type consists of aspecial phosphor glass between lead filters,encased in a bakelite housing. The dosimeter,which is small, lightweight, and rugged, is wornon a chain around the neck. This dosimeter willmeasure accumulated doses of gamma radiationfrom 25 r to 600 r. A special instrument, theCP-95/PD computer- indicator, is required toread the DT-60/PD dosimeter.Film badge dosimeters are nonself- readingdevices for measuring both gamma radiationand beta radiation in low or moderate ranges.A film badge uses a special photographic filmwhich is surrounded with moisture-proof andlight-proof paper and shielded with lead, cadmium,plastic, or other shielding material. Bythe use of different shielding materials, the badgecan be made to differentiate between gammaradiation and beta radiation. Laboratory techniquesare required for the development andreading of the film.Detection of Biological AgentsBasically, there are two possible approachesto the problem of detecting biological agents.Physical detection is based on the measurementof particles within a specified size range (andpossibly the simultaneous measurement of otherphysical properties of the particles). Researchis currently being done with a view to developingeffective methods of physical detection.Biological detection involves growing the organisms,examining them under a microscope,and subjecting them to a variety of biochemicaland biologicaltests. Although positive identificationcan frequently be made by biologicaldetection methods, the procedure is difficult,exacting, and relatively slow. By the time abiological agent has been detected and identifiedin this fashion, personnel may well be showingsymptoms of illness.Biological detection may be divided into twophases: the sampling phase and the laboratoryphase. The sampling phase may be a joint responsibilityof damage control personnel and ofthe medical department. The laboratory phaseis obviously a medical department responsibility.Detection of Chemical AgentsVarious detection devices have been developedfor the detection and identification ofchemical agents. Most of these devices indicatethe presence of chemical agents by color changeswhich are chemically produced. To date, nosingle detector has been developed which iseffective under all conditions for all chemicalagents. A number of devices, including airsampling kits, papers, crayons, silica gel tubes,and indicator solutions, are in naval use. Someof these devices are also useful in establishingthe completeness of decontamination and in estimatingthe hazards of operating in contaminatedareas.MONITORING AND SURVEYINGThe monitoring and surveying of any areacontaminated with NBC contamination is a vitalpart of NBC defense. In general, monitoring76