Principles of naval engineering - Historic Naval Ships Association

Chapter 4-PREVENTIVE AND CORRECTIVE DAMAGE CONTROLare required to work in contaminated areas.The purpose of biological decontamination is todestroy the biological agents. The purpose ofchemical decontamination is to remove or neutralizethe chemical agents so that they will nolonger be a hazard to personnel.Decontamination operations may be both difficultand dangerous, and personnel engaged inthese operations must be thoroughly trained inthe proper techniques. Certain operations, suchas the decontamination of food and water, shouldbe done only by experts qualified in such work.However, all members of a ship's companyshould receive adequate training in the elementaryprinciples of decontamination so that theycan perform emergency decontamination operations.After an attack, data from NBC surveys willbe used to determine the extent and degree ofcontamination. Contaminated personnel must bedecontaminated as soon as possible. Beforedecontamination of installations, machinery, andgear is undertaken, appraisals of urgency mustbe made in light of the tactical situation.Radiological DecontaminationRadiological decontamination neither neutralizesnor destroys the contamination; instead,it merely removes the contamination from oneparticular area and transfers it to an area inwhich it presents less of a hazard. At sea,radioactive waste is disposed of directly overthe side. At shore installations, the problem ismore difficult.Several methods of radiological decontaminationhave been developed; they differ ineffectivenessin removing contamination, in applicabilityto given surfaces, and in the speed withwhich they may be applied. Some methods areparticularly suited for rapid gross decontamination;others are better suited for detaileddecontamination.GROSS DECONTAMINATION.-The purposeof gross decontamination is to reduce the radiationintensity as quickly as possible to a safelevel— or at least to a level which will be safefor a limited period of time. In gross decontamination,speed is the major consideration.Flushing with water, preferably water underhigh pressure, is the most practicable way ofaccomplishing gross decontamination. Aboardship, a water washdown system is used to washdown all the ship's surfaces, from high to lowand from bow to stern. The washdown systemconsists of piping and a series of nozzles whichare specially designed to throw a large spraypattern on weather decks and other surfaces.The washdown system is particularly effectiveif it is activated before the ship is exposed tocontamination; a film of water covering theship's surfaces keeps the contaminating materialfrom sticking to the surfaces. Figure 4-9shows a water washdown system in operation.Manual methods may be used to accomplishgross decontamination, but they are slower andless effective than the ship's washdown system.Manual methods that may be used by ship'sforce include (1) firehosing the surfaces withsalt water, and (2) scrubbing the surfaces withdetergent, firehosing the surfaces, and flushingthe contaminating material over the side. Figure4-10 shows men performing gross decontaminationoperations by manual scrubbing.Steam is also a useful agent for gross decontamination,particularly where it is necessaryto remove greasy or oily films. Steamdecontamination is usually followed by hosingwith hot water and detergents.DETAILED DECONTAMINATION.-As timeand facilities permit, detailed decontaminationis carried out. The main purpose of detaileddecontamination is to reduce the contaminationto such an extent that only a minimum ofradiological hazard to personnel would persist.Three basic methods of detailed decontaminationmay be used— surface decontamination,aging and sealing, and disposal. Each of thesemethods has a specific purpose; one method canoften be used to supplement another. Surfacedecontamination reduces the contamination withoutdestroying the utility of the object. In agingand sealing, radioactivity is allowed to decreaseby natural decay and any remaining contaminationis then sealed onto the surface. The disposalmethod merely consists of removing contaminatedobjects and materials to a place wherethey can do little or no harm.Biological DecontaminationThe methods available for biological decontaminationinclude scrubbing, flushing, heating,and the use of disinfectant sprays, disinfectantvapors, and sterilizing gases. The method to beused in any particular case depends upon thenature of the area or equipment to be decontaminatedand upon the nature of the agent (ifthis is known).79