The "Multiplication Factor" is the ratio of the total number of fission or fission-dependent neutrons produced in a time interval to the total number of neutrons lost by absorption and leakage during the same interval.
Applicable units are those of quantitykind:MultiplicationFactor
http://en.wikipedia.org/wiki/Neutron_multiplication_factor
The "Multiplication Factor" is the ratio of the total number of fission or fission-dependent neutrons produced in a time interval to the total number of neutrons lost by absorption and leakage during the same interval.
http://www.iso.org/iso/catalogue_detail?csnumber=31895