Like sunlight transmits energy to the earth, nuclear radiation also transmits energy to the medium that absorbs the rays (particles). Here we talk about two concepts: one is the radiation irradiation medium, the other is the medium to absorb radiation. The former is expressed in terms of irradiation and the latter in terms of absorbed dose.
(a) the amount of exposure (X)
The amount of exposure (X) is the amount of X-rays or γ-rays in the air caused by the number of ionization of the legal unit of measurement for the library per kilogram, the symbol C / kg. In the past, used to use the unit is the roentgen (symbol for the R), is defined as follows: radiation in the air per kilogram produces a symbolic ions in the charge of 2.58 × 10-4C (due to a ions). carries a charge of 1.602 × 10-19C, or produces 1.61 × 1015 ion pairs/kg of air). Exposure is defined by the equation
Nuclear radiation fields and radiological surveys
The equation: dQ denotes the amount of a symbolic charge produced in a mass of dm (in a given volume) of air. The relationship between roentgen and cou/kg is: 1C/kg = 3.8277 × 103R.
(ii) Exposure rate
Definition is: the amount of irradiation per unit of time, which can be written as
Nuclear Radiation Fields and Radiological Surveys
The unit is C/kg-s. In the past, the units have been used as R/s (roentgen/second) or R/h (roentgen/hour); There is also μR/h (gamma, gamma). The relationship is
1γ=1μR/h=10-6R/h=7.17×10-14C/kg
(III) Radiation Absorbed Dose
Exposure can be measured in terms of the dose effect of radiation on the air, but it does not apply to the deposition of energy by radiation on human tissue. Hence the introduction of radiation absorbed dose. In the International System of Units (SI), the unit of absorbed dose used is: Gray (Gy). It is defined as the energy deposition of radiation forming 1 J in 1 kg of medium, i.e.
1Gy (Gorey) = 1 J/kg (J/kg); 1Gy = 100 rd
Rad (rd) is the unit previously used.
(D) dose equivalent
Dosimetry found that 0.01Gy (1rd) of fast neutron absorbed dose produced biological damage and 0.1Gy (10rd) of γ-ray radiation absorbed dose produced the same biological damage, for this reason, the proposed ability to respond to a specific type of radiation-induced injury to the ability of the quality of the factor Q multiplied by the absorbed dose, constituting the dose equivalent. The International System of Units (SI) unit now used is the Sievert, symbolized as Sv. In the past, the unit used was the rem (rem).
Dose Equivalent (Sievert) = Absorbed Dose (Gorey) x Q
Quality Factor Q value: for X-rays, gamma rays, and beta rays it is 1; for thermal neutrons it is 2.3; for fast neutrons it is 10; and for alpha particles it is 20.
1 Sv = 103mSv = 100rem
(v)Dose Rate
The Absorbed Dose as mentioned earlier. There is no concept of time. Dose rate represents the dose absorbed per unit hour. Therefore, the relationship between dose, dose rate and time is
Dose = dose rate × time
Dose rate is measured in Sv/h, mSv/h; or Gy/h, mGy/h.
(F) flux density (φ)
Flux density is also known as the rate of injection of rays or energy, and can be described by the number of particles or photons passing through an area of 1m2 in 1s. The number of particles or photons passing through an area of 1m2 in 1s can be described. Assuming that a point source emits neutrons (or particles) at a rate of Qn[n(neutrons)/s], at a distance r, the flux density is
Nuclear radiation field and radiological survey