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Radiation Safety Training Dose limits and Dosimetry Washington State University Radiation Safety Office. Units Used in Radiation Safety. erg. Rad . Sievert. Roentgen. joule. Curie. Rem. Gray. Becquerel. Units Definitions Really it’s not that hard. Energy. ft lb, erg, joule,
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ftlb, erg, joule,
electron-volt (1 eV = 1.6 x 10-19 joules)
Others: meV, keV, MeV, GeV, TeV
1 erg = 10−7 joule
James Prescott Joule
One foot-pound is the amount of energy expended when one pound-force acts through a distance of one foot along the direction of the force.
An electron volt (symbol eV) is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electrostatic potential difference of one volt.
Roentgen (symbol R) (coulomb/kg)
1 R = 2.58 x 10-4 C./kg
(1 esu charge in 1.293 mg of air)
87.6 ergs/gm for air
Wilhelm Conrad Röntgen
The röntgen or roentgen (symbol R) is a unit of measurement for ionizing radiation, and is named after the German physicist Wilhelm Röntgen. Adopted in 1928, 1 R is the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (esu) in 1 cm³ of dry air at standard temperature and pressure (STP). This corresponds to the generation of approximately 2.08×109 ion pairs.
Rad (or Gray in SI units)
1 R 95 ergs/gm for tissue
1 rad = 100 ergs/gm
1 gray (Gy) = 0.01 J/kg = 100 rad
The rad (radiation absorbed dose) is a unit of absorbed radiation dose, with symbol rad. It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. It was restated in SI units (Gray) in 1970 as the dose causing 0.01 joule of energy to be absorbed per kilogram of matter. To gauge biological effects the dose in rads is multiplied by a 'quality factor' which is dependent on the type of ionizing radiation. This modified dose is now measured in rems (roentgen equivalent mammal, or man)
Rem (or Sievert in SI units)
H = QD (H in rem if D in rad)
Q is quality factor (Effects of Type of Radiation)
1 for e, x,
2-10 for neutrons (E - dependent)
10 for protons
20 for alpha
1 sievert (Sv) = 100 rem
A “Rem” is a unit of measurement also known as “dose equivalent” which numerically describes the relative amount of biological damage which occurs from doses of ionizing radiation. The rem is derived by the product of the dose received in rads and a quality factor which is unique to each type of radiation. This equates the effectiveness of each type of radiation to cause biological damage. The rem is used to report doses to persons or organs.
1 calorie=amount of energy to heat up 1 milliliter of water 1 degree C.A millirem measures the amount of radiation energy absorbed into the tissue.
1000 millirems =1 rem =0.01 Gy
1 Gy=1 Joule /kg times a quality factor to adjust for the type of radiation (alpha, beta, or gamma)
But how much energy is that?
Therefore 4.16 Gy would produce the same amount of energy it would take to heat up 1 milliliter of water 1 degree C.
Curie (or Becquerel in SI units)
1 Becquerel (Bq) = 1 dis./sec
1 curie (Ci) = 3.7 x 1010 dis./sec
1 curie (Ci) = 2.22 x 1012 dis./min
1 mCi = 37 MBq
A “Curie” is a unit of measurement which quantifies the amount of radioactivity present as a disintegration rate. One Curie (Ci) is referenced as the amount of radioactivity present in 1 gram of radium and is equivalent to 3.7 x 1010 disintegrations per second (DPS).
An annual limit, the more limiting of:
(1) Total effective dose equivalent, or----------------5 rem (0.05 Sv)
(2) Sum of deep dose equivalent and committed dose equivalent to any organ or tissue (not lens of eye)—50 rem (0.5 Sv)
AND—Annual limits to lens or eye, to skin, and to extremities of:
(1) Eye dose equivalent of -----------------------------15 rem (0.15 Sv)
(2) Shallow dose equivalent to skin or extremity—50 rem (0.5 Sv)
Print the Prenatal Radiation Exposure Statement form on page S90.75.16.Return the original signed form to the Radiation Safety Office. Retain a copy for departmental files.
The Radiation Safety Office issues Personnel Dosimetry
About 850 Persons are badged at WSU.
Worn on index finger of dominant hand, with the white face turned towards the radiation source.
OSL Body Badge
Worn on torso, below chin
and above waist
Internal Dosimetry - A technique used to monitor the dose from radioactive materials taken into the body.
Urinalysis: Analyzing urine samples to determine the amount of radionuclide excreted by the human body.
Thyroid monitoring: To determine the amount of radioactive iodine (125I and 131I) in the thyroid.
Whole body counting: This procedure would be performed elsewhere, if necessary.
If you are required to wear a badge (dosimetry). Once a year you will receive an exposure report. This report tells you what your radiation exposure was for the previous year. This person received 16 mrem (0.016 rem). Far below the 5 rem limit. ALARA As Low As Reasonably Achievable.