Radiation protection counter

Exempt Radioactive Wastes. The radioactive waste classification system in the United States does not include a general class of exempt waste (see Table 1.1). Rather, many products and materials that contain small amounts of radionuclides (e.g., specified consumer products, liquid scintillation counters containing 3H and 14C) have been exempted from requirements for use or disposal as radioactive material on a case-by-case basis. The various exemption levels are intended to correspond to low doses to the public, especially compared with dose limits in radiation protection standards for the public or doses due to natural background radiation. However, the exemption levels are not based on a particular dose, and potential doses to the public resulting from use or disposal of the exempt products and materials vary widely. 

The standard sources have been designed in order to allow the calibration of all the classical detectors of a, p, e, y, n, X radiation (ionisation chambers, Geiger-Miiller or proportional counters, scintillation or solid-state counters, etc.). They are classified as alpha sources, electron sources, beta sources, gamma sources, neutron sources. X-ray sources, heat flux sources, and sources for radiation protection dose meters. 

A short description of possible nuclear applications of boron-based materials had been done by Potapov (1961) in an old overview that included the nuclear power industry (e.g., control rods of nuclear reactors) solid-state electronics (e.g., counters of neutrons and neutron energy sensors) radiation chemistry (e.g., acceleration of technological processes) etc. For these purposes, "B nuclei are useless, but °B nuclei are useful due to a large cross section of interaction with thermal neutrons, °B converts them into heavy ionizing particles. Besides, °B isotope is applicable for neutron radiation protection (Stantso 1983) and also in medicine, e.g., in boron neutron capture therapy (BNCT) for treating cancer tumors (Desson 2007). 

At all stages of medical care, the treatment of highly contaminated individuals will require special facilities or isolated facilities with the specif procedures that limit the spread of contamination and disposal of contaminated waste. For the deteetion of radioaetive eontam-ination, radiation equipment should be available, such as specialized radiation monitoring instruments, whole body counter, and iodine thyroid counter. Usually a radiation protection officer or health physicist performs the measurements. For the purpose of dose reeonstraction, different instruments and methods can be used, such as electronic paramagnetic resonance (EPR) spectrometry and cytogenetic dosimetry. Because of this, collection of various tissues (blood, hair, and teeth) and clothes of exposed persons should be organized. Provisions (plastic bags, labels, etc.) should be made in advance. 

Monitoring occupational radiation exposure is a fundamental aspect of radiation protection. This can be done by measuring radiation fields with a common handheld instrument such as a Geiger-Mueller Counter and, if exposure conditions are predictable and relatively low (i.e., less than 10% of the regulatory limit), expected exposures can be calculated and documented. Alternately, regular radiation field survey measurements can be performed, and personnel dosimeters are issued to workers. 

An expensive method is the use of nuclear radiation to obtain information on the level in an apparatus. The nuclear sensor is mounted at one side, and at the other side a scintillation counter is fixed near the surface of the apparatus. Both systems are sheathed with lead-screen shields to give protection from nuclear radiation. A continous level indicator using nuclear radiation is very complicated and therfeore seldom applied. 

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. 

In plants, phenolic metabolites can stimulate cellular protective response coupled to antioxidant function in the presence of biotic and abiotic stress (Briskin 2000). Among abiotic stress, UV light induces phenolic phytochemicals through the phenylpropanoid and flavonoid glycoside pathways as a protective of metabolic response (Logemann et al. 2000). This UV inducible phenolic phytochemical response can help to counter intracellular ROS produced in response to UV. This UV-inducible phenolic response ean be coupled to antioxidant enzyme response (Rao 1996) to attenuate damage from UV radiation. 

Preamplifiers are used in nuclear channels in which the variable of interest is the rate of pulses occurring within the detector. Since they are installed in places with high radiation fields, their main purpose is to increase the pulse amplitude with a minimum of electronic components. Therefore, the output pulse of the preamplifier is not, suitable for count rate meters, and additional signal conditioning is necessary. Linear amplifiers provide the necessary means to discriminate the undesirable noise and to properly shape the pulses, making them compatible with counters, ratemeters and spectroscopy analyzers. Conventional solid state amplifiers are an essential part of reactor protection systems, NIM modules are preferred, but many research reactors I C systems have integrated nuclear channels. Both of them have shown to be reliable and safe. 

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