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B

background:
The dose or dose rate (or an observed measure related to the dose or dose rate), attributable to all sources other than the one(s) specified.
Strictly, this applies to measurements of dose rate or count rate from a sample, where the background dose rate or count rate must be subtracted from all measurements.  However,background is used more generally, in any situation in which a particular source (or group of sources) is under consideration, to refer to the effects of other sources.  It is also applied to quantities other than doses or dose rates, such as activity concentrations in environmental media.

  • natural background: The doses, dose rates or activity concentrations associated with natural sources or any other sources in the environment which are not amenable to control.
    This is normally considered to include doses, dose rates or activity concentrations due to natural sources, global fallout (but not local fallout) from atmospheric nuclear weapon tests and the Chernobyl accident.

barrier:
A physical obstruction that prevents or inhibits the movement of people, radionuclides or some other phenomenon (e.g. fire), or provides shielding against radiation.

! The term ‘chemical barrier’ is sometimes used in the context of waste disposal, to describe the chemical effect of a material which enhances the extent to which radionuclides react chemically with the material or with the host rock, thus inhibiting the migration of the radionuclides.  As defined above, this is not strictly a barrier (unless the material also constitutes a physical barrier) but the effect may equivalent to that of a barrier, and it may therefore be convenient to regard it as such.

becquerel (Bq):
Name for the SI unit of activity, equal to one transformation per second.
Supersedes the curie (Ci).  1 Bq = 27 pCi (2.7 10-11 Ci) approximately.

beyond design basis accident:
See plant states.

bioassay:
Any procedure used to determine the nature, activity, location or retention of radionuclides in the body by direct (in vivo) measurement or by in vitro analysis of material excreted or otherwise removed from the body.

biosphere:
That part of the environment normally inhabited by living organisms.
In practice, the biosphere is not usually defined with great precision, but is generally taken to include the atmosphere and the Earth’s surface, including the soil, surface water bodies, seas and oceans and their sediments.  There is no generally accepted definition of the depth below the surface at which soil or sediment ceases to be part of the biosphere, but this might typically be taken to be the depth affected by basic human actions, particularly farming.
In waste safety in particular, the biosphere is normally distinguished from the geosphere.

buffer:
Any substance placed around a waste package in a repository to serve as an additional barrier to: stabilize the surrounding environment; restrict the access of groundwater to the waste package; and reduce by sorption the rate of eventual radionuclide migration from the waste.
The above definition is clearly specific to waste safety.  The term buffer (e.g. in buffer solution) is also used, in its normal scientific sense (and therefore normally without specific definition), in a variety of contexts.

bypass:
1.   A device to inhibit, deliberately but temporarily, the functioning of a circuit or system by, for example, short circuiting the contacts of a relay.

2.   A route that allows fission products released from a reactor core to enter the environment without passing through the containment or other enclosure designed to confine and reduce a release in the event of an emergency.
This route may be established intentionally by the operator or as a result of the event.