Radiation dose

The dose rate DR) per unit activity (Q) maintained within the thyroid is given by Soldat et al. (1973)  

The average equilibrium radiation dose aquivalent rate per pCi I contained within the thyroid is calculated to be 0.57, 0.24, 0.08, and 0.061 mrem y for 1-, 4-, and 14-year olds, and adults, respectively. As the effective energy absorbed per disintegration (c) remains fairly constant with age (0.061 — 0.065 MeV par disintegration) (Soldat, 1976), the substantial decrease in dose equivalent per pCi with increasing age results almost entirely from the rapid increase in thyroid gland size. 

A steady dietary intake of one pCi ingested daily would lead to an equilibrium burden of 8.7 pCi in the thyroids of 1 to 4 year old children and 22 and 43 pCi in those of 14-year olds and adults, respectively, resulting in dose equivalent rates of 4f9, 2.1,1.7 and 2.6 mrem y for the 1-, 4-, and 14-year olds, and adults, respectively. 

Thyroid dose equivalents resulting from burdens detailed in Table 4.5 were determined from the above factors. The radiation dose equivalent rate for the adult thyroid resulting from food items exposed to air concentrations of 1 pCi m would be about 4 rem y (Table 

Dietary source Average Thyroid dpse rapivalent te (mrem y pCj m )  

---

High-current EC-50 betatron with maximal energy of accelerated electrons equaled to 50 MeV and radiation dose power 220 Gr/min on the distance of Im from the target [3] was made for experimental physical researches and activated analysis. 

Beer s absorption law (1) for the penetrating radiation is used to correlate the penetrated wall thickness (w) and the radiation dose I (lo - radiation dose at w=0, p - absoiption coefficient) ... 

Modem NDT film systems (with Pb screens) are very linear X-ray detectors. This is shown in fig.l for different NDT film systems and a X-ray tube at 160 kV. Note that for histoncal reasons the film response curve is often plotted as film density versus log (radiation dose), which hides this linear relationship. The film density is the difference between the measured optical film density and the fog density Db of the film base. 

In order to minimize the radiation dose, the inspection time is limited to 30 seconds of exposure (programmable) after which the X-ray on/off shutter will shutter off the X-rays and the block must be unloaded. A timer will keep the operator informed of the time that has elapsed. 

MAPPscan is a manual ultrasonic testing system connected to an acoustic positioning system.. The system is developed as a consequence of the increased radiation doses in nuclear plants The system has the same flexibility as manual scanning with the same accuracy and the possibilties to collect, store and evaluate the UT data as with mechanised Ultrasonic systems The positioning system is based on spatial acoustic triangulation and have an accuracy of better than 1.0 mm within its recommended range. 

Potential to reduce radiation doses for a small and specially trained group of UT evaluation experts. 

The system has proven to be a powerful tool for inspections in the Nuclear industry with the potential of reducing the radiation doses for a highly qualified group of personnel and at the same time ensure a high quality and reproducibility of testing... 

Radiation protection, ie, the limits on radiation dose to workers and the pubHc are specified. Exposure is maintained as low as reasonably achievable... 

Radiation dose limits at a disposal site boundary are specified by the NRC as 25 x 10 Sv/yr (25 mrem/yr), a small fraction of the average radiation exposure of a person in the United States of 360 x 10 /Sv/yr (360 mrem/yr). Protection against nuclear radiation is fully described elsewhere... 

The safety record for transport of radioactive materials including spent fuel and wastes is excellent. Information about transportation of radioactive materials including waste is managed by DOE. Codes such as RADTRAN that can calculate pubHc radiation dose owing to the passage of shipments have been developed. The maximum dosage from such shipments is a very small fraction of the typical annual radiation dose from all other sources. 

Most of the data on radiation health effects have come from medical monitoring of Japanese atomic bomb survivors. For survivors who received radiation exposures up to 0.10 Sv, the iacidence of cancer is no greater than ia the geaeral populatioa of Japanese citizens. For the approximately 1000 survivors who received the highest radiation doses, ie, >2 Sv, there have been 162 cases of cancer. About 70 cases would have been expected ia that populatioa from aatural causes. Of the approximately 76,000 survivors, as of 1995 there have beea a total of about 6,000 cases of cancer, only about 340 more cases than would be expected ia a group of 76,000 Japanese citizens who received only background radiation exposure (59). 

For radiation doses <0.5 Sv, there is no clinically observable iacrease ia the number of cancers above those that occur naturally (57). There are two risk hypotheses the linear and the nonlinear. The former implies that as the radiation dose decreases, the risk of cancer goes down at roughly the same rate. The latter suggests that risk of cancer actually falls much faster as radiation exposure declines. Because risk of cancer and other health effects is quite low at low radiation doses, the iacidence of cancer cannot clearly be ascribed to occupational radiation exposure. Thus, the regulations have adopted the more conservative or restrictive approach, ie, the linear hypothesis. Whereas nuclear iadustry workers are allowed to receive up to 0.05 Sv/yr, the ALARA practices result ia much lower actual radiatioa exposure. 

In common with other pharmaceuticals, the two primary requirements for success are safety and efficacy. Safety is deterrnined both by chemical toxicity and radiation dose deflvered to the patient. 

The 140 KeV photons emitted by Tc are accompanied by few conversion and Auger electrons and no beta-particles which increase the radiation dose without adding to the imaged information, and no gamma- or x-rays of other energies. These other gamma- or x-rays, if substantially lower in energy. 

Radiation dose for radiopharmaceuticals in a given patient can only be estimated. There are significant variations in dose from internally deposited... 

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. 

Eig. 12. Absorption spectmm of irradiated impure vitreous siUca, Heraeus fused quart2, after a radiation dose of 10 Gy (10 rad) (208). The main impurity... 

Chemical dosimeters based on ferrous sulfate, ferrous cupric sulfate, or ceric sulfate are generally used. Color-change process indicators are also used, but these cannot measure the radiation dose, only the extent of sterilization. 

Bunte salts have bacterial, insecticidal, and fungicidal properties, and are also used as chelating agents (qv) or surfactants (qv) (97,98). Bunte salts have been tested for preirradiation protection for mammals exposed to lethal radiation doses (99,100) (see Radioprotectiveagents). 

An algorithm has been developed to predict the thermal conductivity degradation for a high thermal conductivity composite ( 555 W/m-K at room temperature) as a function of radiation dose and temperature [33]. The absence of irradiation data on CFCs of this type required the use of data from intermediate thermal conductivity materials as well as pyrolitic graphite to derive an empirical radiation damage term [14, 17, 19, 25, 26]. 

---