8. Glossary of some of the terms used
Annual dose equivalent limit: The value of the annual dose equivalent that must not be
exceeded, according to the ICRP system of dose limitation.1
Annual limit on intake (ALI): ALI is a secondary limit for the internal exposure of
radiation workers. It is the smaller value of intake of a given radionuclide in a year by
Reference Man2 which would result in either a committed effective dose equivalent of
50 mSv or a committed dose equivalent in the lens of the eye of 150 mSv or in any
other organ or tissue of 500 mSv.
Approved medical practitioner: A medical practitioner responsible for the health
surveillance of occupationally exposed workers and whose capacity to act in this
respect is recognised by the competent authority.
Area, controlled: An area where workers might receive doses in excess of three-tenths
of the occupational dose equivalent limits for workers engaged in radiation work during
the anticipated working period, and where appropriate controls (such as restricted
access, individual assessment of dose and special health surveillance) are accordingly
Area, supervised: An area where radiation levels are such that annual exposure is most
unlikely to exceed three-tenths of the occupational dose equivalent limits but may
exceed one-tenth of those limits, and where special forms of supervision (such as area
monitoring) are accordingly applied.
"As low as reasonably achievable": Synonym for optimisation (see Optimisation).
Becquerel, Bq: The name of the unit of activity. The activity, A, of an amount of a
radioactive nuclide in a particular energy state at a given time is the quotient of dN by
dt, where dN is the expectation value of the number of spontaneous nuclear transitions
from that energy state in the time interval dt:
A = dN
The SI unit of activity is s –1. The special name of this unit is becquerel (Bq):
1 Bq = 1 s –1.
The unit of activity previously used was the curie (Ci):
1 Ci = 3.7 × 1010 Bq.
1 See ICRP: "Recommendations of the International Commission on Radiological Protection",
2 See ICRP: Report of the Task Group on Reference Man, Publication No. 23 (Oxford,
Pergamon Press, 1975).