Loose Contamination Research Articles

Activity estimates of localised gamma emitting radionuclides using a GR-135 survey meter

During the operation of high energy accelerators activated materials are commonly created. The activity and isotopes present in these materials must be characterised for their clearance and release from the facility, or to ascertain their duration of stay in a radiological storage area. An activity estimate method using a gamma detecting GR-135 survey meter, which has the ability to collect an energy spectrum, is presented. Using several reference radioactive sources the detection efficiency and dead time of the survey meter were characterised. This information combined with the physical properties of the survey meter, the counting time and the properties of the measured photon energy emissions can be used to calculate an accurate activity estimate for localised activation on accelerator components, or loose contamination on isolated waste materials.

Validation of a Dose Assessment Method to be Used in 18F FDG Loose Contamination Exercises.

Radiological emergency response may require responders to operate in contaminated environments. To provide more realistic training to these individuals, it has been proposed to disperse low amounts of short-lived radioactive material in simulated emergency scenarios. To demonstrate the applicability and safety of such activities, a limited exercise was conducted where 18F was sprayed in a small area and survey activities were executed. A pre-job external radiation exposure dose assessment was performed in preparation for this training. The research presented here compares participant external recorded doses to assessment results in order to validate the dose estimates. Two individuals were used during the dispersion, search, and survey activities. First, a radiation worker mixed 200 MBq Fludeoxyglucose 18F with 470 mL H2O in a weed sprayer and distributed it over a 3 m × 3 m area. After evaporation, an exercise participant performed search and survey activities in the area. Actual whole-body doses measured with optically stimulated luminescence dosimeters were 10 ± 1 μSv for both personnel. Whole-body digital dosimeters read 4.3 ± 0.2 μSv and 3.3 ± 0.5 μSv for the radiation worker and exercise participant, respectively. Actual extremity doses were below the dosimeters' minimum detectable limits for the radiation worker (thermoluminescence dosimeter) and exercise participant (optically stimulated luminescence dosimeter). The dose assessment-predicted whole-body doses were 2.8 ± 0.4 μSv and 3.2 ± 0.1 μSv for the radiation worker and exercise participant, respectively. The estimated dose to the radiation worker's hand was 21.8 ± 3.8 μSv, and the estimated dose to the exercise participant's knee was 13.4 ± 0.6 μSv. The study provided substantial evidence for the validity of the dose assessment method, supporting its use for a larger training exercise.

Particulate size and shape effects in laser cleaning of heavy metal oxide loose contamination off clad surface

This work explores laser assisted removal of uranium-di-oxide and thorium-di-oxide particulates from zircaloy substrate. An electro-optically Q switched Nd-YAG laser operating on three wavelengths of 1064 nm, 532 nm, 355 nm was used as the cleaning tool to compare the efficiency of the decontamination process. Laser assisted surface cleaning that offers the dual advantage of remote operation and minimizing the generation of secondary waste has therefore emerged as the most attractive technique with regard to decontamination of radioactive surface. In case of loose contamination wherein the contaminant particulates are often attached to the substrate surface by short range van-der-wall’s force, the absorption of energy from the incident radiation field by both particulates and substrate can contribute towards generation of cleaning force leading to expulsion of the particulates. It was found that laser parameters like its wavelength, fluence, number of exposures and particulate shape/size play an important role in the cleaning process. A single laser exposure with a fluence of ∼0.3–0.5 J/cm2 was found to be enough to obtain decontamination efficiency of ∼70–80% while removing the contaminants from zircaloy substrate. Subsequent exposure of laser pulses to the contaminants further increases the efficiency of cleaning. Decontamination efficiency was found to be always higher for uranium-di-oxide particulates than virgin thorium-di-oxide particulates under identical cleaning conditions. However, decontamination efficiency of milled thorium-di-oxide particulates was found to be marginally higher than uranium-di-oxide particulates.

Experimental study on encapsulating the loose contamination by atomizing process

Experimental study on encapsulating the loose contamination by atomizing process

Laser-assisted cleaning: Dominant role of surface

Pulsed laser-assisted removal of particulates from substrates has decided advantages over the conventional methods of cleaning. Experiments conducted with loose contamination on metal and transparent dielectric surfaces proved conclusively the dominant role played by the absorption of the incident radiation by the surface towards the generation of the cleaning force as against the absorption in the particulates alone. Further, the presence of transparent/semi-transparent particulates on a metal surface was found to result in an increased absorption of the incident radiation by the substrate. This effect, identified as field-enhanced surface absorption was found to increase with reduction in the average particulate size.

Potential for Contamination during Removal of Radioactive Seeds from Surgically Excised Tissue

The purpose of this study was to determine whether the use of a scalpel or electrocautery to remove radioactive sealed sources ("seeds") from surgically excised tissue could damage the seed and cause it to leak its radioactive contents. Attempts were made to cut or burn Oncura Model 6711 non-radioactive seeds while in pig muscle or on a stainless steel plate. Additionally, one active 125I seed was purposely charred using pressure with an electrocautery knife to see whether the casing could be damaged. Electron microscopy scanning was performed on the dummy seeds to determine if the integrity of the metal casing had been compromised. Two types of leak tests were performed on the active seed to verify the presence or absence of loose contamination. The seed casing was not damaged from either use of a scalpel or electrocautery when the seed was in tissue. The active seed was not found to be leaking after applying pressure with an electrocautery knife while the seed was on a stainless steel plate. We conclude that removal of active Model 6711 seeds from surgically excised tissue can be done safely with a scalpel or electrocautery because constant, firm pressure cannot be applied to the seed. This is likely true for seeds made of similar materials.

Guidelines for Handling Radioactively Contaminated Decedents

The Centers for Disease Control and Prevention recently issued guidelines for medical examiners, coroners, and morticians in dealing with decedents after detonation of an improvised nuclear device (IND) or radiological dispersal device (RDD) (). Partners in this effort included the New York City Office of Chief Medical Examiner and the National Funeral Directors' Association. This paper describes the handling techniques required for loose surface contamination, radioactive shrapnel, and internal contamination caused by inhaling or ingesting radioactive materials from an IND or RDD, and provides suggested guidelines for medical examiners, coroners, and morticians to deal with these situations.

Radiation Protection Issues Related to Canadian Museum Operations

Museums in Canada have been found to possess radioactive items. The origin of the radiation can be broadly categorized as either natural (generally, radioactive ores) or anthropogenic (generally, luminous gauges). Radioluminescent gauges, especially bearing radium (226Ra), can also generate significant radiation fields. This is especially true if many gauges are located in close proximity. In addition, the radon may out-gas from these gauges, and generate a loose contamination problem in enclosed spaces (such as display cases). Radioactive ores, bearing naturally occurring uranium and thorium, can generate radiation fields many times greater than the ambient background levels. In addition, they will increase the ambient radon level and potentially generate loose contamination. In this paper, we discuss the specific results of radiological decommissioning at three museums: the National Air Force Museum of Canada (Trenton, Ontario); the Quebec Air and Space Museum (Montreal, PQ); and the Canadian Museum of Nature (Aylmer, PQ). In addition, a radiological survey performed at Canadian Forces Detachment Mountain View (Mountain View, Ontario) of surplus aircraft is included. The primary conclusion is that museums holding radioactive materials may have detectable levels of loose Ra and progeny contamination. They, therefore, have a requirement to be surveyed for loose contamination periodically with the potential for periodic decontamination caused by radon out-gassing. In addition, public access to displays bearing radioactive material should generally be restricted, and comprehensive radiation safety and security programs at museum facilities should be developed and enacted.

Decontamination and Deactivation of the Power Burst Facility at the Idaho National Laboratory

Successful decontamination and deactivation of the Power Burst Facility located at the Idaho National Laboratory was accomplished through the use of extensive planning, job sequencing, engineering controls, continuous radiological support, and the use of a dedicated group of experienced workers. Activities included the removal and disposal of irradiated fuel, miscellaneous reactor components and debris stored in the canal, removal and disposition of a 15.6 curie Pu:Be start-up source, removal of an irradiated in-pile tube, and the removal of approximately 220,000 pounds of lead that was used as shielding primarily in Cubicle 13. The canal and reactor vessel were drained and water was transferred to an evaporation tank adjacent to the facility. The canal was decontaminated using underwater divers, and epoxy was affixed to the interior surfaces of the canal to contain loose contamination. The support structures and concrete or steel frame walls that form the confinement were left in place. The reactor core was left in place and a carbon steel shielding plate was placed over the reactor core to reduce radiation levels. All low-level waste and mixed low level waste generated as a result of the work activities was characterized and disposed.

Target handling at high-intensity RNB facilities

The increasing scientific demand for new isotopes farther from stability has created a need for dealing with targets and ion sources capable of handling higher primary-beam powers. The induced residual radiation makes hands-on maintenance not possible. However, remote handling of complex systems is difficult and costly. The engineering challenges are to achieve long-term target availability while minimizing radiation exposure to workers and to the environment. In order to realize these goals, it is essential to develop an overall strategy to deal with the prompt radiation, the activated components, the volatile contamination and the loose contamination.

Surface Contamination on Fuel Flasks: Best Practice Advice on Minimising and Measuring Non-Fixed Radioactive Contamination

Knowing the levels of non-fixed radioactive contamination on surfaces is important for the safety of personnel and ensuring conformity with the regulations. Best practice will reduce the generation of loose surface radioactivity and enable it to be assessed with reasonable accuracy. This paper summarises experimental work carried out by the Central Electricity Generating Board/Nuclear Electric into the generation of non-fixed contamination, the mechanisms of the swabbing process and how the swab value relates to the, total loose surface radioactivity. It identifies those factors which are, and are not, important in the generation of non-fixed contamination and its measurement. These factors include: paint condition, time in the pond, decontamination vigour, environmental sources, journey time, flask surface location (top/sidelbottom), area wiped, contact pressure, swab – surface contact geometry, soiling, relative humidity prior to swabbing, effect of liquid water during transport but dried off before swabbing, wetness of surface/swab, water chemical composition, effects derived from UV irradiation on paint before contamination, effects of UV and gamma irradiation on paint previously contaminated. Surface soiling (grime and water) are the only significant generators of loose contamination. Swab reproducibility and precision is improved by circumscribing the contact geometry, area wiped and contact pressure. An in situ method of determining total loose radioactivity by multiple swabbing is presented. Best practice advice for minimising and measuring non-fixed contamination is derived.

The Three Mile Island Unit 2 Reactor Building Gross Decontamination Experiment: Effects on Loose Surface Contamination Levels

In March 1982, the gross decontamination experiment was conducted in the Three Mile Island Unit 2 reactor building (RB). The intent of the experiment was twofold: (a) to determine which of several ...

Transfer of loose radioactive contamination of surfaces in the movement of people

The authors construct a model for assessing the amount and quality of radioactive material transported throughout a nuclear reactor or facility by the motion of people walking back and forth through the plant in the process of discharging their assigned duties. The model accounts for contamination primarily carried on the soles of their shoes and is intended for use in optimizing a monitoring scenario in the plant.

スミヤ法による表面汚染密度の測定に関する実験

Smear survey is carried out in order to measure the amount of loose contamination on the surface. The value measured by the smear method depends on the nature of surface material, contaminants, or smear pressure, therefore, it is desirable to make clear the relations between them for radiation protection. In this work the smear survey was performed in various experimental conditions stated above, and the results obtained were compared with those of field tests.The non-permeable surface materials such as vinyl sheet were contaminated with various radioisotopes and were smeared. These experiments show that 5080% of loose contamination and about 50% of total contamination were detected in the model experimental conditions. On the other hand, the same experiments were also carried out using permeable materials. In this case, 5080% of loose contamination and 250% of total contamination were detected. From these results, it is possible to estimate the amount of surface contamination, by assuming that 10% and 50% of the amount of total contamination are transfered to the smear disk for permeable and non-permeable surface materials with contaminants, respectively.

On the Susceptibility and Decontamination Properties of Surface Finishing Materials

The smear method is compared with an ordinary method for the measurement of decontamination factors. The smear method provides the decontamination factor of loose contamination and generally gives better resuits compared with the ordinary method using the surface contamination detector. However, for the sake of convenience and accuracy, it is preferable to adopt the ordinary method. To improve the decontamination experiment, it was found that more serious attention should be paid to the following contaminated; (2) chemical form of the contaminant, especially its pH; and (3) drying method of contaminant applied to the testing materials. The results of decontamination properties of twenty kinds of materials, most of them newly produced in Japan since 1958, are summarized. The decontamination reagents used are EDTA, HNO/sub 3/ + H/sub 3/PO/sub 4/, HI, and ferric ammonium ciirate. Generally speaking, these newly produced materials are comparatively easily decontaminated by any kind of reagent. In this experiment, P/sup 32/ and I/sup 131/ were used as the contaminant for the most part. It was found that the susceptibility for the former is higher than the litter but, on the contrary, most of the decontamination reagents work better for P/sup 32/ than I/sup 131/. This comes probably frommore » the fact that P/sup 32/ has a very low pH and is corrosive. (A.G.W.)« less