InHour
InHour is a unit of reactivity of a nuclear reactor. It stands for the inverse of an hour. It is equal to the inverse of the period in hours. One InHour is the amount of reactivity needed to increase the reaction from critical to where the power will increase by a factor of e in one hour. The unit is abbreviated ih or inhr, and is usually measured with a reactimeter. See also *Per cent mille A per cent mille or pcm is one onethousandth of a percent. It can be thought of as a "millipercent". It is commonly used in epidemiology, and in nuclear reactor engineering as a unit of reactivity. Epidemiology Statistics of crime rates, mort ... References Units of measurement {{energystub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] 

Per Cent Mille
A per cent mille or pcm is one onethousandth of a percent. It can be thought of as a "millipercent". It is commonly used in epidemiology, and in nuclear reactor engineering as a unit of reactivity. Epidemiology Statistics of crime rates, mortality and disease prevalence in a population are often given in Nuclear Reactivity In nuclear reactor engineering, a per cent mille is equal to onethousandth of a percent of the reactivity, denoted by Greek lowercase letter rho. Reactivity is a dimensionless unit representing a departure from criticality, calculated by: :\rho=(k_1)/k_ where keff denotes the effective multiplication factor for the reaction. Therefore, one pcm is equal to: :1~\text = \rho \cdot 10^5 This unit is commonly used in the operation of lightwater reactor sites because reactivity values tend to be small, so measuring in pcm allows reactivity to be expressed using whole numbers. Related units * Percentage point difference of 1 part in 100 * Percentage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] 