Radiation contamination control measures

Will work require radiation or noise control measures, monitoring for biological or chemical air contaminants, or medical surveillance ... 

In comparing the three main types of hazards found in biomedical laboratories, chemical, biological, and radiological, only radiation has the unique characteristic of ease of detection of its presence with very few exceptions, the presence of contamination or radiation areas is readily detected by fairly inexpensive equipment, so that steps can be taken to prevent continued exposure or spread of the hazard. Thus, many of the control measures in handling radioisotopes use instruments that can detect radiation. 

Radiation protection control is one of most important considerations in the program. Dose equivalent rate and radioactive concentration are measured daily and reported by health physicists. Each work plan is made on the basis of this measurement and work areas are classified into various categories. For example, radioactive contamination is classified into three groups C-l(less than 4 Bq/cm ), C-2(4 to 40 Bq/cm and C-3(more than 40 Bq/cm ). Work conditions, such as respiratory protection and personal protective clothing, are then decided according to this categorization. Data on radiological safety... 

Three carbon fibre-reinforced polyimides were exposed to UV radiation at 177C, at three different intensities for three different times, so that the product of intensity and time was a constant. Intensities of 1,2 and 3 suns, where one sun is the power in space at one earth-sun distance, were used, for a time periods of 500, 250 and 167 h. The samples were characterised by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, thermomechanical analysis and dynamic mechanical analysis. Measurement of bulk properties showed no difference between samples exposed to heat and UV radiation, and control samples. Surface analysis by XPS showed an apparent decrease in carbonyl concentration on the surface of some exposed samples. This was correlated to surface contamination by a silicone-containing material. 3 refs. 

As an example let us consider the pentacene/samarium interface (Koch et al, 2002). Samarium has a low work function ((/>m — 2.7 eV), which is comparable to E a from pentacene (— 2.7 eV). Thus, if A 0, the condition Ep, should provide efficient electron injection because in this case fp and LUMO are nearly aligned. In order to avoid contamination that may alter the instrinsic m, h and homo values, such heterostructures have to he prepared in ideally clean conditions, imposing the use of UHV. The UPS experiments performed with synchrotron radiation are shown in Fig. 4.24. After measuring (pM of the clean samarium surface (2.7 eV) as described above, increasing amounts of pentacene are controllably deposited onto the samarium surface. The survey spectra of the valence states and a close-up view of the energy region near E are shown in Figs. 4.24(a) and (b). 

The protection follows three stages prevoition, supervision, and after-control. Preventive measures include use of fume hoods, or-boxes, radiation shielding, tongs, etc., as discussed above. The supervision stage involves the use of radiation instrum ts to monitor the radiation level (see Ch. 8). Small TLD, film or pocket pen dosimeters are used for individual monitoring ( 7.9). For spills and contamination of hands, shoes, etc., special contamination instruments (counters) are used which are more sraisitive than the monitoring dose instrumrats. 

The spectrometer permits confirmation of the observed radionuclide by its spectrum, within the limitations of spectral distortion by energy losses and the radiation background associated with the measurement. It also permits setting the lower and upper energy discriminators for optimum values for each radionuclide of interest. The energy ranges beyond the region of interest usually are measured at the same time to confirm the absence of contaminant radionuclides. Two or three radionuclides may be detected simultaneously by such discriminator control... 

Screening measurements of incident response samples begin as soon as possible after sample receipt and logging. A necessary first step is prescreening to prevent a sample from being taken to a laboratory if its radionuclide content is unsuitably high for the usual controls of personnel radiation exposure and contamination of the analyst, the laboratory, and radiation detectors. External radiation is measured with conventional low-level radiation monitors that include the G-M detector and... 

Detector quality control records are reviewed to assure that control samples and the radiation background have been measured recently and that the detectors in use are within control limits (Section 11.2.10). Brief control source and background measurements are performed before the screening process begins to assure that detectors continue to operate appropriately and have not been contaminated recently. The detection limit in terms of activity per sample is calculated for all radionuclides of interest to determine whether a null result will meet radionuclide detection requirements for the submitted samples. 

Examination of the contamination of surfeces using IMS measurements was also described by Seng, who was concerned with quality control in curing of surface films. An IMS analyzer was used to detect trace amounts of coating and ink components that remained unlinked during the ultraviolet (UV) radiation curing process. ... 

Properly calibrate radiation measurement instruments before each use. Train personnel in handling radiation wastes. Each department that generates radioactive wastes should develop written procedures that cover handling of, transportation, and disposal. Properly secure and store all waste materials and designate controlled areas. Dispense or draw materials only behind a protective barrier. Label refrigerators that contain stored materials. Notify the radiation control officer when receiving a contaminated shipment. 

In general, exposure to radiation during all activities for the establishment of the safe enclosure was significantly lower than expected. Due to the low level of contamination in the controlled and supervised areas, it was possible to furnish the radiological proof required for downgrading of the controlled area to the supervised area and for release of buildings from the supervision under nuclear law by means of a relatively small number of measurements. 

When monitoring for contamination, measurements of surface activity are generally made for the purpose of controlling radiation exposure and/or contamination levels. 

Before items are removed from any contamination zone, and in any case before they are removed from controlled areas, they are required to be monitored as appropriate (Ref [2], para. 1.23) and suitable measures should be taken to avoid undue radiation hazards. 

Area monitoring may include measurements of radiation dose rates, airborne activities and surface contamination. In the controlled areas, fixed continuously operating instruments with local alarm and unambiguous readout should be installed to give information on the radiation dose rates. Any such instruments shall have ranges adequate to cover the expected levels. 

Radiation control Remote high dose-rate measuring instrument Dust monitor Contamination inspection apparatus Waste package contamination and dose rate monitor... 

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