Committed dose equivalent

Once radioactivity is placed internally it becomes an internal emitter. Internal emitters are used infrequently either therapeutically (actually implanted in a tumor) or with accidental exposure via ingestion or inhalation or penetration through skin internal emitters may be removed only with varying degrees of difficulty (Harley, 2001). Usually, they cannot be removed simply or easily and an irreversible committed equivalent dose is said to exist. 

For radionuclides with half-lives zero to 3 months the equivalent dose is equal to the armual dose of the year of intake (Harley, 2001). It is often convenient to estimate the fraction of the committed equivalent dose which remains. For a radionuchde with a half-life of 3 months, after 1 year of exposure, it had undergone the passage of four half-fives so tfiat fraction of dose delivered was (1 /2 ) 94% of... 

Most of the properties mentioned in the previous paragraph are taken into account in the ALI and DAC concept (ALI = Annual Limits of Intake DAC = Derived Air Concentration, based on the ALI value). 1 ALI corresponds to an annual committed equivalent dose of 50 mSv. 

After an elapsed time T following an intake of radioactive substances, the committed equivalent dose is defined as ... 

Absorbed dose, organ dose, equivalent dose, effective dose, committed equivalent dose, or committed effective dose, depending on the context. The modifying terms are often omitted when they are not necessary for defining the quantity of interest. 

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... 

The SI unit of committed effective dose is Sv, the same as for effective dose. Similarly, one can derive a committed equivalent dose. The quantity of dose commitment differs from the committed dose only by the upper integration limit. It is defined as the infinite time integral (t = oo) of the per caput dose rate Hi or E) ofthe population due to a specified event. The unit of the dose commitment is the same as for committed dose. Both individual dose commitment and collective dose commitment can be defined. 

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. 

The sum of the effective dose resulting from exposure to external sources and the committed effective dose incurred from all significant inhalation pathways during the early phase. Committed equivalent dose to the thyroid and to this can may be five and 50 times larger, respectively. 

Committed equivalent dose to the thyroid from inhalation. 

Occupational - the committed effective dose equivalent (Internal) and annual effective dose equivalent (external) combined... 

The ALI is the activity of a radionuclide that can be taken into the body in a year, by inhalation or ingestion, without exceeding a committed effective dose equivalent (CEDE) of 5 rem/year or a committed dose equivalent to any organ of 50 rem/year, whichever is more limiting. The total effective dose equivalent TEDE is the sum of the CEDE and any penetrating external dose (10 CFR 20). If any external dose is present the ALI must be reduced by a proportional amount to ensure that the dose limits are not exceeded. For example, if a worker received an external dose of 1 rem/year, the ALI would have to be reduced by 20% to ensure that the TEDE did not exceed 5 rem/year. 

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)... 

Total effective dose equivalent (TEDE) is the sum of the deep-dose equivalent (for external exposure) and the committed effective dose equivalent (for internal exposure). 

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. 

Derived intervention levels (DIL) are concentrations of radioactivity in food whose consumption would deliver a committed effective dose equivalent equal to the most limiting of the protection action guides (PAGs) developed by FDA (1998). 

Committed effective dose equivalent the sum, over all relevant tissues... 

By considering all possible transfer routes, one can estimate what amount of a radionuclide released to the environment may end up in plants, animals, or man. When these figures are combined with the dose conversion factors ("committed effective dose equivalent per unit intake", according to ICRP) in Table 18.12, it is possible to calculate the dose received by man from intake of a radionuclide in the environment. The dose conversion factors dep d on the mode of intake (usually only inhalation or ingestion). Thus... 

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 ... 

The fundamental dosimetric quantity used is the absorbed dose. The equivalent dose and the effective dose are also important quantities. Special circumstances might be characterized by committed dose, kerma dose, and some other dose quantities and factors. 

A committed effective dose equivalent or total effective dose equivalent to any member of the public no greater than 4 mrem may result annually from exposure to and consumption of groundwater contaminated by releases from an LLRW disposal facility. 

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