Chemical decontamination procedures

The chemical composition and the structure of the contamination layer oxides in the primary systems depend highly on the reactor type (PWR, BWR) and also on the operational history of the plant. The optimum decontamination process to be applied, therefore, must be selected and, if necessary, optimized to meet the task in question. In particular, when components and systems are to be decontaminated, different structural materials and, consequently, oxide layers of different composition are involved, resulting in more stringent demands on the decontamination procedures to be applied. 

The Can-Decon process developed by AECL and London Nuclear and originally applied to the Canadian CANDU reactors (LeSurf, 1977) uses a citric acid -oxalic acid solution. When the decontamination is carried out at temperatures around 90 °C, only a rather poor process efficiency is achieved therefore, in most of the applications temperatures around 120 °C have been used, leading to an overpressure in the systems of about 0.3 MPa, resulting in complications in process engineering. Under such conditions, decontamination factors between 10 and 20 were obtained when the process was applied to US BWR plants. From these applications no adverse effects on the base materials have been reported. In the early 1980 s tests under aggravated conditions yielded stress corrosion phenomena in sensitized steel SS 304 as a result, the importance of the process decreased markedly for a certain time. It has to be pointed out, however, that the conditions 

In the Dilute Chemical Decontamination (DCD) process developed by Westing-house, a solution of citric acid, oxalic acid, EDTA and an inhibitor is applied, resulting in decontamination factors on the order of 10, as was determined in laboratory studies higher efficiencies were obtained when a pre-oxidation step was included (Murray et al., 1985). In order to improve the decontamination effectiveness, it was proposed that the spent solution be circulated over a porous DC electrode where dissolved ions are reduced. The Fe ion generated in this manner is assumed to attack the contamination layer in a one-electron reaction, thus accelerating the dissolution of the oxides (Murray and Snyder, 1985). However, this process seems not yet to have been applied to operating light water reactor plants. 

In the NS-1 process developed by Dow Chemical, organic chelating agents such as ethylenediamine tetra-acetic acid plus organic inhibiting additives were used at temperatures around 125 °C and an associated overpressure in the systems of about 0.4 MPa. From several applications to piping and systems in US BWR plants, decontamination factors between 10 and 100 have been reported in some cases pre-oxidation steps had to be applied in order to improve the efficiency of the process (Anonymous, 1985). 

One of the most frequently reported decontamination processes is the Lomi process (Low Oxidation State Metal Ions), which was originally developed by the British CEGB for removal of corrosion product deposits from the fuel bundles of the Steam Generating Heavy Water Reactor (SGHWR). Since Fe always is the 

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A publication summarises all the then available technical evidence related to the Seveso accident, and recommends operational criteria to ensure safety in commercial processes to produce trichlorophenol [4], All the plant scale incidents were characterised [ 1 ] by the subsequent occurrence of chloracne arising from the extremely toxic and dermatitic compound 2,3,7,8-tetrachlorodibenzodioxin (structure IX, p. S-3), formed dining the thermal runaway reaction and dispersed in the ensuing explosion. It is also extremely resistant to normal chemical decontamination procedures, and after the 1968 explosion, further cases occurred after transient contact with plant... 

Decontamination. If contaminated equipment or material does not have to be used immediately, natural aeration is an effective decontaminant procedure, as most chemical agents, including the bHster and V-agents, are volatile to a certain degree. Wind accelerates their evaporation and hastens their dissipation. Rain and dew may also cause sufficient hydrolysis of some agents. Sunlight increases the surface temperatures of military equipment and thus accelerates agent evaporation. 

Potential effects of inclement weather (i.e., using wet procedures during cold weather can cause both operational and maintenance problems) Potential effects of hazards on worker S H (i.e., vapors from chemical decontamination solutions may be hazardous on inhalation or contact with skin, or may be flammable)... 

The primary mission of the Decontamination Element is to turn chemical/biological victims into patients through mass decontamination procedures by establishing a site capable of providing initial and sustained operational decontamination of Force personnel (rescue workers), ambulatory, and non-ambulatory patients. The Decontamination Element also handles decontamination of CBIRF members, attachments, vehicles, and equipment that have entered the incident site controls access into and out of the incident site handles processing of surety material and evidence while maintaining chain of custody through the site and handles limited area decontamination of the incident site. 

WASTE DISPOSAL METHOD All decontaminated material should be collected, contained and chemically decontaminated or thermally decomposed in an EPA approved incinerator, which will filter or scrub toxic by-products from effluent air before discharge to the atmosphere. Any contaminated protective clothing should be decontaminated using HTH or bleach and analyzed to assure it is free of detectable contamination (3X) level. The clothing should then be sealed in plastic bags inside properly labeled drums and held for shipment back to the DA issue point. Decontamination of waste or excess material shall be accomplished in accordance with the procedures outlined above with the following exception ... 

External decontamination procedures are designed to minimize internal contamination of patients and the individuals providing care. Radionuclides on the intact skin surface rarely produce a high enough absorbed dose to be hazardous to patients or to medical staff. However, this is not the case for chemical hazards. Prior to implementing decontamination procedures, a patient should be moved to an upwind position outside of the area of contamination. 

During radiological decontamination efforts, caregivers should consider the chemical nature of the contaminant, the medical needs of the patient, the seriousness and extent of contamination, and the presence of wounds. Prior to implementing decontamination procedures, remove all outer clothing from the contaminated individual and place the clothing in a sealed container such as a plastic bag. Save clothing so... 

Decontamination of JACADS will require chemical, mechanical, and thermal processing. The removal of critical structural components and systems from buildings will have to be planned to ensure structural stability. Residuals of any of the agents processed at JACADS (HD, GB, and VX) may be exposed during disassembly activities. These residuals will be harmful to anyone in the immediate area If they are vaporized, airborne agent concentrations could be harmful, so decontamination procedures for equipment, waste streams, and building materials must ensure that agent residues are destroyed, and the destruction must be verified. 

This subject is discussed in the following refs Refs 1)US Dept of the Army TM3-220, "Decontamination (Nov 1943) 2)US Army Supply Bulletin SB5-52, Decontamination Procedures (July 1945) 3)US Depts of the Army and the Air Force TM3-215 AFM 355-7, "Military Chemistry and Chemical Agents (1963) 4).AMC Safety Manual AMCR 385 224, Sect 3, Headquarters, US Army Materiel Command, Washington, DC (June 1964)... 

Check on the quality of equipment decontamination procedures involving the "swiping" of sterile filter paper over sampling equipment after decontamination has occurred, followed by chemical analysis of the field swipe and an unused filter paper. Volume 2(10). 

What is the criterion that determines whether a decontamination procedure was effective It is not the absolute absence of any chemical contaminants in the equipment blank. Important for the project are only the contaminants of concern and their concentrations. For site investigations, when no information is available on existing pollutants, it may be important that no contaminants of concern are present in equipment blank samples above the laboratory PQLs. On the other hand, for site remediation projects, the presence of contaminants of concern in equipment blank samples may be acceptable, if these concentrations are only a fraction of the action levels. The decision to decontaminate equipment and the selection of the acceptability criteria for equipment blanks are made in the DQO process based on the intended use of the data. 

Children with special health care needs will require additional considerations during mass casualty or disaster care. These considerations include decontamination procedures following radiation or chemical exposure for children using wheelchairs, ventilators, or oxygen and decontamination procedures for children with gastrostomy tubes, tracheostomy tubes, indwelling bladder catheters, and indwelling central venous catheters. Replacement supplies would be needed once the cutaneous decontamination is completed. Such supplies may not be readily available, so provisions must be made to secure these items or to have comparable clean or sterile supplies on hand. 

Immature cognitive function can put children at risk diuing a chemical attack (Rotenberg and Newmark, 2003). Children lack the abdity to discern threat, to protect themselves, or to follow directions. Infants, toddlers, and young chddren do not have the motor skdls to flee from the site of an incident (CEH/CID, 2000). This can adversely impact their avoidance of a contaminated area and decontamination in the event of exposure. During decontamination, procedures for children who have been separated from their caregivers must be taken into consideration. Without guidance, children may not be able to follow directions for the decontamination process (Wheeler and Poss, 2003). 

Dismantling of decommissioned nuclear reactors requires special procedures. The outer parts can be handled like normal industrial waste, whereas the inner parts, mainly the reactor vessel and some core components, exhibit high radioactivity due to activation. Radioactive deposits on the inner surface of the reactor vessel may be removed by chemical decontamination. Altogether, the relatively large volumes of LLM and MLW which are obtained by dismantling are further processed and then preferably enclosed in concrete or bitumen. 

Since 1966 the basin has been operated as a closed system. The basin water is continuously recycled through a diatomaceous earth filter, and no contaminated water is released to ground. Makeup water is added to the basin by spraying casks as a part of the cask decontamination procedure. The water level is controlled by adding additional water to the basin if needed, or by purging a small stream from the basin to the plant waste evaporator. An increase in the concentration of radionuclides and dissolved solids in the water has occurred as a result of the recycle process. Consequently, a plant-scale ion-exchange unit was installed in July 1973, based on the results of laboratory studies, to remove radionuclides from the basin water. The fuel storage basin water at that time had the approximate chemical and radiochemical composition shown in Table I. 

The ultra-sensitive technique of LEAFS was developed and exploited for the analysis of snow and ice to be carried out at the Institute of Spectroscopy of the Russian Academy of Science (ISAN) (46). This technique allows the direct determination of toxic metals in polar snow and ice to be carried out at and below the pg/g level in sample volumes of less than 100 pi. This is an important issue considering that very often the volume of sample obtained after the decontamination procedures amounts to just a few tens of milliliters in the best case and that this must be subdivided into different aliquots for a complete chemical characterisation. 

Most states will have a designated resource center, such as a regional Poison Control Center, which can provide information for caring for specific hazardous chemical exposures, including appropriate decontamination procedures. 

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