Radiation area activity

The use of two separate electrical or mechanical zones of detectors, both of which must be actuated before the confirmation of a fire or gas detection. For example, the detectors in one zone could all be placed on the north side of a protected area, and positioned to view the protected area looking south, while the detectors in the second zone would be located on the south side and positioned to view the northern area. Requiring both zones to be actuated reduces the probability of a false alarm activated by a false alarm source such as welding operations, from either the north or the south outside the protected area. However this method is not effective if the zone facing away from the source, sees the radiation. Another method of cross zoning is to have one set of detectors cover the area to be protected and another set located to face away from the protected area to intercept external sources of nuisance UV. If welding or lighting should occur outside the protected area, activation of the alarm for the protected area would be inhibited by second... 

Photoallergic responses to sunscreen products represent an area where chemical components not known to produce dermal allergic responses are activated by solar radiation to produce ACD. I45 46 It is hypothesized here that in these instances, electromagnetic radiation may activate the skin to adsorb and/or absorb species that do not so react without the incident radiation. Alternatively, the molecular species themselves are excited by the radiation to molecular states that make them more reactive to skin. Chemicals exhibiting photoallergic contact dermatitis include oxybenzone, butyl methoxy dibenzoylmethane, methoxycinnamate, and benzophenone—all molecules that are readily photoexcitedJ45 ... 

The field of aquatic photochemistry encompasses a wide diversity of areas within environmental science. Natural waters receiving solar radiation are active photochemical reactors. Within these reactors, primary and secondary processes are occurring. Heterogeneous reactions are associated with both living and nonliving particulate matter. Naturally occurring humic substances are relatively efficient initiators of photochemical reactions. Many xenobiotic chemicals in natural waters undergo either direct or indirect photochemical transformations. 

Those portions of 10CFR20 specifying permissible occupational dose levels and levels of radiation and activity concentrations in unrestricted areas are consistent with all of the selection bases and, therefore, are included as top-level regulatory criteria. 

A.26. Records of occupational radiation doses. Inspection personnel should selectively review records of individual occupational doses, including internal and external doses. Activities should be observed to ensure that procedural and management controls are effective. This includes controls for radiation areas and contamination areas as well as inspection of activities for internal and external dosimetry. Exposures of personnel that result in the operator s reference levels for effective doses or intakes being exceeded should be noted. Records of radiation protection training and retraining should be assessed. 

The exposures should be kept low through practices such as minimization of cladding defects, use of corrosion resistant materials, reduction of formation of long lived corrosion and activation isotopes, very low primary circuit coolant leakage, minimization of maintenance in high radiation areas and use of remote handling tools and robots. 

To minimise personnel exposure from valve operations, motor operated, air operated or other remotely actuated valves are used where justified by activity levels and frequency of use. Where manual valves are used, either valve extenders or shielding is provided such that personnel need not enter a radiation area for valve operation. 

Pipes carrying radioactive materials are routed through controlled access areas properly zoned for the level of activity. Where it is necessary that radioactive piping be routed through corridors or other low radiation areas, shielded pipe ducts, or distance separation are provided. Where practicable, radioactive and non-radioactive piping are separated. 

Most of the activity from any such steam and water leakage is associated with activation products which have been retained by the pipework lagging. This, incidentally, has given a useful method of leak detection when the reactor is shut down and depressurized. The feed heater cell is classified as a restricted radiation area principally because it contains bled st earn pipes and the primary circuit polishing plant. However, access has been possible at all times for visual inspection, and some maintenance work has been performed with the reactor at full power. 

A. 1239. This section shall present a diagram showing the radiation fields in normally occupied areas of the facility and in areas where maintenance activities will be performed. Estimated annual occupancy data for the facility radiation areas shall be used to show that the expected doses are acceptable for the major functions, such as reactor operation, conduct of experiments, normal maintenance, radwaste handling, refuelling and in-service inspection. An estimate of the annual dose at the boundaries of the restricted area shall be provided. 

Uptake of Natural Uranium by Native Plants Grown in a High Background Radiation Area Table 5 Activity concentration of uranium isotopes in some leafy plants... 

The physical properties of the Selenium also offer big advantages with respect to radiation shielding and beam collimation. Within the comparison of radiation isodose areas the required area-radius for a survey of 40pSv/h result in a shut off area that is for Selenium only half the size as for iridium. Sources of similar activity and collimators of same absorbtion value (95%) have been used to obtain values as mentioned in Table 3 below. 

The detector setup consists of four 256 x 256 pixel amorphous silicon technology sensor flat panels with 0.75 x 0.75 mm pixel size, having an active area of 192 x 192 mm [5j. These sensors are radiation sensitive up to 25 MeV and therefor well suited for detecting the LINAC radiation. The four devices are mounted onto a steel Irame each having the distance of one active area size from the other. With two vertical and two horizontal movements of the frame it is possible to scan a total area of about 0.8 x 0.8 m with 1024 x 1024 pixel during four independent measurements. 

Nonetheless, these methods only estimate organ-averaged radiation dose. Any process which results in high concentrations of radioactivity in organs outside the MIRD tables or in very small volumes within an organ can result in significant error. In addition, the kinetic behavior of materials in the body can have a dramatic effect on radiation dose and models of material transport are constandy refined. Thus radiation dosimetry remains an area of significant research activity. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

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