Irradiation radiation quantities

GROSSWENDT, B. and HOHLFELD, K. (1982). Angular dependence of specified depth dose equivalent quantities in the ICRU sphere for photon irradiation, Radiat. FYot. Dosim. 3, 169-174. 

Fig. 5.14 Relationships between the four radiation quantities of irradiation...

Note that the actinic flux is always related to a given altitude (depth z, Fig. 2.11) in the atmosphere (earth s surface at z = 0). It is important to distinguish the actinic flux 5 (A) from the spectral irradiance /(A), which refers to energy arrival on a flat surface with a fixed spatial orientation (Table 2.14) and which is the most common measured radiation quantity ... 

As Mackenzie had suggested. Chalk River had a lot of work to do before it could produce isotopes in commercial quantities. Its research chemistry department was busy experimenting with the techniques required to extract isotopes from irradiated elements. In April 1947, laboratory space was set up specifically for isotope work. When NRX started up on July 22, 1947, the scientists first concentrated on getting to know the machine. They then began experiments to find our how much radiation exposure was required to produce different isotopes. In August, while the reactor power was still only at one hundred watts, they irradiated a quantity of sodium carbonate for thirty hours. When pulled from the reactor it yielded a small amount of sodium-24 - the first isotope produced at Chalk River."... 

Nuclear activation analysis (NAA) is a method for qualitatively and quantitatively detg elemental compn by means of nuclear transmutations. The method involves the irradiation or bombardment of samples with nuclear particles or high-energy electromagnetic radiation for the specific purpose of creating radioactive isotopes from the stable or naturally-occurring elements present. From the numbers, types and quantities of radioactive elements or radionuclides, it is possible to deduce information about the elemental compn of the original sample... 

Lind [2] has defined radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It should be distinguished from radiation damage which refers to structural transformation induced by irradiation, particularly in the solid state. The distinction is not always maintained, perhaps unconsciously, and sometimes both effects may be present simultaneously. Following a suggestion of M. Curie around 1910, that ions were responsible for the chemical effects of radioactive radiations, the symbol MjN was introduced to quantify the radiation chemical effect, where M is the number of molecules transformed (created or destroyed) and N is the number of ion pairs formed. Later, Burton [3] and others advocated the notation G for the number of species produced or destroyed per 100 eV (= 1.602 x 10 J) absorption of ionizing radiation. It was purposely defined as a purely experimental quantity independent of implied mechanism or assumed theory. 

Absorbed dose is a fundamental and basic physical quantity which can be used in all fields where ionizing radiations are used. It is directly related to the physical, chemical, and biological effects produced by the irradiation. The concept of absorbed dose thus has broad applications and is indeed widely used. Metrological institutions provide standards and calibration of instruments in terms of absorbed dose. 

When the entire body or parts of the body are irradiated externally, individual tissues and organs receive different absorbed doses. In order to relate the absorbed doses in tissue from non uniform irradiation to radiation detriment in humans, a quantity is required which reflects the relative effects of different types of radiation and the relative radiosensitivity of the irradiated organs and tissues. 

The principal data available to determine or E directly from ifpdO) are conversion coefficients which give the quotient of or E and /fp(lO) [i.e., He/[Hp(10)1 or /[ifp(10)]). The unit for each of the three quantities is Sv therefore, these conversion coefficients are dimensionless. Such conversion coefficients have been derived from calculations for a number of idealized conditions for irradiation by monoenergetic photons of mathematically described reference adult anthropomorphic phantoms. The conversion coefficients are a function of photon energy, photon beam direction, surface of the phantom on which the radiation is incident, and location where //p(lO) is being evaluated on the phantom. 

Dose In the context of chemicals, the temi dose means the amount, quantity, or portion of the chemical exposed to or applied to the target (e.g., a human being). It may also refer to a consistent measure used in toxicological testing to determine acute and chronic toxicities. An alternate definition is die amount of ionizing radiation energy absorbed per unit mass of irradiated material at a specific location, such as a part of die human body, measured in REMS, or an inanimate body, measured in rads. 

Knowledge of the volatile components of irradiated and nonir-radiated beef is reviewed. Concurrent and nonconcurrent irradiation procedures produce the same compounds but in different relative quantities. Storage of irradiated beef decreases irradiation flavor and the quantity of volatile constituents. Methional, 1-nonanal, and phenylacetaldehyde are of primary importance in beef irradiation off-flavor produced under the conditions described. 

The contribution to irradiation off-flavor of individual components was unknown, though the sulfur- and nitrogen-containing substances were suspected to be significant because of their inherent strong unpleasant odors. Merritt (9) suggested that dimethyl sulfide, 1-hexene, and n-hexane were important components of irradiation odor and pointed out that the quantity of these compounds produced increased directly with radiation dose. 

The major components identified among the volatiles produced in haddock upon irradiation are benzene and toluene and the sulfur compounds. These compounds may be expected from the radiation-induced degradation of protein. The only carbonyl compounds found are acetone and methyl ethyl ketone, and these are present in only moderate amount. Trace quantities of low molecular weight hydrocarbons were also found. The detection of hydrocarbons, even in trace amounts, led us to question whether their origin was in the protein or in the small amount of fat present in the haddock. 

Radiation Dose Limits. For routine exposure of individual members of the public to all man-made sources of radiation combined (i.e., excluding exposures due to natural background, indoor radon, and deliberate medical practices), NCRP currently recommends that the annual effective dose should not exceed 1 mSv for continuous or frequent exposure or 5 mSv for infrequent exposure. The quantity effective dose is a weighted sum of equivalent doses to specified organs and tissues (ICRP, 1991), which is intended to be proportional to the probability of a stochastic response for any uniform or nonuniform irradiations of the body (see Section 3.2.2.3.3). 

Maize starch may be separated after irradiation into several fractions, based on solubility in alcohol and aqueous alcohol. The size of the fractions and their composition depends on the radiation dose, as shown in Table X which also shows the distribution of organic products of destruction (aldehydes and carboxylic acids) in particular fractions.118 The relations presented in this Table are S-shaped. Under irradiation with increasing doses, the destruction of starch obviously increases. The nature of the increase of acidity in com starch has also been studied by Athanassiades and Berger.119 Thollier and Guilbot120 have conducted similar studies on potato starch, and Raffi et al99 have extended their studies to more varieties of starch. The results expressed as free and total acidities, as well as the quantity of formic acid at equilibrium water content, are given in Table XI. These data vary rather nonlinearly with increase of the irradiation dose and water content. 

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