Radiation committed equivalent dose

For the purpose of demonstrating compliance with dose limits, the sum of the personal dose equivalent from external exposure to penetrating radiation in the specified period and the committed equivalent dose or committed effective dose, as appropriate, from intakes of radioactive substances in the same period shall be taken into account. 

Committed doses are defined in cases of intakes of radioactive materials, mainly by ingestion, inhalation, or absorption through the skin, in terms of internal radiation impact. In most cases, the quantities of committed absorbed dose, committed equivalent dose, and committed effective... 

Accidents resulting in deterministic health effects will be very rare, and usually this will occur among employees or other professionals. However, in the case of a lost or stolen source, limited number of the general public may receive doses that can lead to deterministic health effects. Such a situation requires special medical care and supportive treatment for the early effects of acute radiation. In the event of internal exposure, especially by long-lived ra onuclides, decorporation might be considered, even if the dose is below the threshold for deterministic health effects. The decision about decorporation levels should be based on committed equivalent dose to the organs and the effective committed dose. 

A measure of the radiation received or absorbed by a target. The quantities termed absorbed dose, organ dose, equivalent dose, effective dose, committed equivalent dose or committed effective dose are used, depending on the context The modifying terms are often omitted when they are not necessary for defining the quantity of interest. 

The SITP is a quantity derived from the Annual Limit on Intake (ALI), an internationally accepted concept that has been acknowledged by the Government s Radioactive Waste Management Committee (RWMAC) as a valid method of establishing equivalent hazards of different waste types. The ALI is a derived limit for the permissible amount of radioactive material taken into the body of an adult radiation worker by inhalation or ingestion in a year. The ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in either a committed effective dose equivalent of 0.05 Sv or 0.5 Sv to any individual organ or tissue. 

F. Radiation Dose (committed dose equivalent, committed effective dose)... 

The Food and Drug Administration (FDA) develops standards for radioactive material concentrations in food (FDA 1998), and medical devices used in radiation therapy (FDA 1997). The FDA recently updated its guidance document that presents recommended action levels for radionuclides in foods, both domestic and imported (FDA 1998). These derived intervention levels (DILs) are estimated levels in food that could lead to individuals receiving a radiation equivalent dose equal to the FDA protection action guide (PAG) that is set as the more limiting of either 0.5 rem (5 mSv) for committed effective dose or 5 rem (50 mSv) committed dose equivalent to any individual tissue or organ. Table 8-2 presents the most restrictive DILs for strontium. 

One remaining barrier to significant injury, electric shock (>50 volts AC), radiation exposure (one event >1000 mr uptake, intake or Committed Effective Dose Equivalent [CEDE]) or Industrial Hygience Exposure (>3 times OSHA limits), exceed criticality limit or double contingency is not maintained... 

Dose limits means the permissible upper bounds of radiation doses. These are usually set for a calendar year. They apply to the dose equivalent received during the set interval, the committed effective dose equivalent resulting from the intake of radioactive material during the interval or the effective dose equivalent received in 1 year The external dose and the internal dose must be combined so as not to exceed the permissible limits. The following equation can be used to compute the relative amounts of each, for the annual intake Ij of nuclide J ... 

In the BSS [2] and in the 1990 Recommendations of the ICRP [6], the approach to calculating the committed effective dose is based on that used for the calculation of committed effective dose equivalent, although as a result of improved information on the late effects of radiation on the tissues of the body some changes have been made to the values of tissue weighting factors and a greater munber of tissues now have specified weighting factors (see Table A-in). 

Schlenker RA. 1986. Comparison of intake and committed dose equivalent permitted by radiation protection systems based on annual dose equivalent and committed dose equivalent for a nuclide of intermediate effective half-life. Health Phys 51 207-213. 

Current federal and state regulations limit radiation workers doses to a total effective dose equivalent (TEDE) of 5 rem/year and a committed dose equivalent to any organ, other than the lens of the eye, of 50 rem/year (EPA 1988c USNRC 1995a). These limits apply to the sum of external and internal doses. The limits are upper limits, and an important philosophy in radiahon protection is to keep radiation doses as low as reasonably achievable (ALARA). 

Table 3.3 summarizes the radiation exposure doses due to the industrial exploitation of phosphate rock, expressed in terms of collective effective dose equivalent commitments resulting from the decision to use a unit mass of marketable ore to accomplish a defined purpose, as reported by UN Scientific Committee on Effects of Atomic Radiation (United Nations, 1982). 

The annual occupational dose limit to an adult radiation worker is the more limiting of (1) total effective dose of 5 rem (0.05 Sv) or (2) the sum of deep-dose equivalent and the committed dose equivalent to any individual organ or tissue, other than the lens of the eye, being equal to 50 rem (0.5 Sv). 

A substance which represents a hazard within the body due to its radioactivity is referred to as radiotoxic. The radiotoxicity depends on the properties of the radiation and on a number of physical, chemical, and biological conditions such as mode of intake (via air, in water or food, through wounds, etc.), the size of the ingested or inhaled particles, their chemical properties (e.g. solubility), metabolic affinity, and ecological conditions. Most of these conditions are considered in the ALI concept. ALI Annual Limits of Intake) and D AC Derived Air Concentrations, from the ALI value) and other relevant data are presented in Table 18.12. An annual intake of 1 ALI corresponds to an annual committed dose equivalent of 50 mSv. 

Radiotoxicity depends on energy deposition in tissue or organs by the radionuclide, the specific tissue exposed to the radionuclide, and the tissue radiation sensitivity. Energy deposition by a radionuclide is a function of its emitted radiations and half-life. Biokinetic studies have identified for most radionuclides of interest the pattern of movement through the body and the effective turnover rate (the sum of the biological and radioactive turnover rates). Biokinetic information also identifies the appropriate type of sample to be collected among blood, urine, feces, saliva, breath, hair, teeth, nasal swipes, and tissue obtained incidental to unrelated operations, and collection frequency. The measured radionuclide concentrations are combined with biokinetic information to calculate the committed dose equivalent, the indicator of radiation impact on the subject (NCRP 1987b). 

The estimated 50-year dose commitment from plutonium for people in the north temperate zone due to atmospheric tests conducted before 1973 is 0.2 mrad (0.002 mGy) to the bone lining cells (Eisenbud 1987). [The gray is an SI unit of absorbed dose and is equal to 0.01 ram.] The average annual dose equivalent from all background radiation to an individual residing in the United States is estimated to be 360 mrem (3.6 mSv) (NCRP 1987). [The sievert is an SI unit of dose equivalent and is equal to 0.01 rem.]... 

The committed dose equivalent is the dose of radiation that a specific organ or tissue receives from an intake of radioactive material over a specified period of time. Once... 

Although during normal operation of research reactors exposure of the public due to the release of radioactive materials in the environment is expected to be negligible, a site-related assessment of such exposure should be performed prior to operation. The main objective of this assessment is to demonstrate compliance with the system of dose limitation as described in detail in IAEA Safety Series No. 9 "Basic Safety Standards for Radiation Protection 13). These evaluations are normally required by regulatory authorities and include estimating the effective dose equivalent for the most exposed members of the public (critical group) and collective effective dose equivalent commitment of the population ("collective dose"). 

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