BLOCK 7: IONIZING RADIATION - Unit 4: Radiation Units (complete)

Question 1

The rate of decay of a radioactive source or the number of nuclear disintegration events occurring over a period of time.

Answer 1

ACTIVITY

The higher the activity, the more disintegrations there are per unit of time and, thus, the greater the amount of radiation that is emitted.

Question 2

The SI unit for activity

Answer 2

Becquerel (Bq), where 1 Bq is equal to one disintegration per second.

Question 3

The historical unit for activity

Answer 3

Curie (Ci). One Ci is equal to 3.7 x 1010 Bq.

Question 4

Gamma and x-ray exposure is expressed in units of _______________.

Answer 4

ROENTGEN (R)

Question 5

Unit referring to the amount of ionizations occurring in a mass of air at any given time. It applies ONLY to gamma and x-ray radiation. There is no SI unit defined for expressing radiation exposure (in air).

Answer 5

Roentgen (R)

Question 6

Alpha and beta particle radiation is expressed in _______________, which is simply the number of particles detected by a radiation detecting instrument each minute.

Answer 6

COUNTS PER MINUTE (CPM)

CPM is not a measure of activity or exposure, but can be used with known characteristics of the detector to infer the activity of the source or exposure from it.

Question 7

Refers to energy absorbed per unit of any material.

Answer 7

DOSE

Question 8

When ionizing radiation interacts with the human body, it deposits a portion of its energy in body tissues. The amount of energy absorbed per unit weight of the organ or tissue is called _______________.

Answer 8

ABSORBED DOSE

Question 9

Absorbed dose is expressed using which units (conventional and SI)?

Answer 9

conventional unit rad (radiation absorbed dose), or the SI unit Gray (Gy)

Question 10

One Gy is equal to _____ rad.

Answer 10

One Gy is equal to 100 rad.

Question 11

A person’s biological risk, or the risk that a person will suffer health effects from an exposure, is measured in which units (conventional and SI)?

Answer 11

conventional unit rem (Roentgen equivalent man) or the SI unit Sievert (Sv)

Question 12

Units describing absorbed dose are not an acceptable measurement of radiation injury. To compensate for these differences, radiation dose is expressed as dose equivalent. _______________ are used to determine the dose equivalent from the absorbed dose.

Answer 12

WEIGHTING FACTORS

Question 13

The International Commission on Radiological Protection (ICRP) Report 103 assigned a weighting factor to each type of ionizing radiation (alpha and beta particles, gamma rays, and x-rays), depending on that type’s ability to transfer energy to the cells of the body. These numbers are known as _______________.

Answer 13

QUALITY FACTORS (QF)

Question 14

The best way to determine a person’s dose is using a _______________, but it can also be calculated using the dose rate and time exposed.

Answer 14

DOSIMETER

Question 15

The amount of radiation absorbed per unit of time.

Answer 15

DOSE RATE

It is typically expressed using any of the exposure units, such as rem, per hour. Knowing the dose rate allows us to determine how long a person may be exposed without exceeding an allowable dose.