Question

MC 7/9

± Study of Plutonium Levels in a Human Population

Radiation can be measured according to activity, exposure, or its effect on biological tissue. Units of curies (Ci) and disintegrations per second (dps) measure activity. The rad measures exposure, where rad stands for radiation absorbed dose. The rem measures biological effect, where rem stands for roentgen equivalent man. RBE is a multiplication factor known as relative biological effectiveness and is approximately 1 for beta and gamma radiation and 10 for alpha radiation.

The following conversion factors relate these quantities:

1 Ci1 radnumber of rems===3.7×1010 dps1×10−2 J/kg tissue(RBE)(number of rads)

Note that the conversion factors between curies and disintegrations per second and between rads and joules per kilogram of tissue are exact (i.e., they contain an infinite number of significant figures). The RBE, however, is approximate and has only one significant figure because it varies with the dose rate, total dose, and type of tissue affected.

Tests on human subjects along the East Coast of the United States in 1965 and 1966, following the era of atomic bomb testing, revealed quantities of about 1.31 pCi of plutonium radioactivity (alpha radiation) in a test subject.

Part A

How many disintegrations per second does this level of activity imply?

Express your answer numerically in disintegrations per second.

Hints

dps

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