Per cent mille

Last updated
Visualisation of 1%, 1%0, 1%00, 1 pcm and 1 ppm as fractions of the large block (larger version) Visualisation parts per 1 block.svg
Visualisation of 1%, 1‰, 1‱, 1 pcm and 1 ppm as fractions of the large block (larger version)

A per cent mille or pcm is one one-thousandth of a percent. [1] It can be thought of as a "milli-percent". It is commonly used in epidemiology, and in nuclear reactor engineering as a unit of reactivity.

Contents

Epidemiology

Statistics of crime rates, mortality and disease prevalence in a population are often given in "per 100000". [2] [3]

Nuclear Reactivity

In nuclear reactor engineering, a per cent mille is equal to one-thousandth of a percent of the reactivity, denoted by Greek lowercase letter rho. Reactivity is a dimensionless unit representing a departure from criticality, calculated by: [4]

where keff denotes the effective multiplication factor for the reaction. Therefore, one pcm is equal to: [5]

This unit is commonly used in the operation of light-water reactor sites because reactivity values tend to be small, so measuring in pcm allows reactivity to be expressed using whole numbers. [6]

See also

Notes

  1. SCALE: A Comprehensive Modelling and Simulation Suite for Nuclear Safety Analysis and Design. Available from Radiation Safety Information Computational Center at Oak Ridge National Laboratory as CCC-785. Oak Ridge, TN: Oak Ridge National Laboratory, June, 2001. Version 6.1. ORNL/TM-2005/39
  2. "Number of Infections and Incidence* per 100,000 Persons | FoodNet | CDC". 28 September 2018.
  3. "GHO | by category | Homicide - Estimates by country".
  4. Merljak, Vid. "Reactivity measurements" (PDF). University of Ljublj. Retrieved September 17, 2017.ana
  5. "Reactivity". nuclear-power.net. Retrieved September 17, 2017.
  6. "percent mille – pcm – unit of reactivity". nuclear-power.net. Retrieved September 17, 2017.


Related Research Articles

Percentage Number or ratio expressed as a fraction of 100

In mathematics, a percentage is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", although the abbreviations "pct.", "pct" and sometimes "pc" are also used. A percentage is a dimensionless number ; it has no unit of measurement.

Parts-per notation Set of pseudo units to describe small values of miscellaneous dimensionless quantities

In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million, parts-per-billion, parts-per-trillion and parts-per-quadrillion. This notation is not part of the International System of Units (SI) system and its meaning is ambiguous.

Per mille Unit for parts per thousand

Per mille is an expression that means parts per thousand. Other recognised spellings include per mil, per mill, permil, permill, or permille.

Molar concentration is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L or mol⋅dm−3 in SI unit. A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M. To avoid confusion with SI prefix mega, which has the same abbreviation, small caps or italicized M are also used in journals and textbooks.

Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity.

A temperature coefficient describes the relative change of a physical property that is associated with a given change in temperature. For a property R that changes when the temperature changes by dT, the temperature coefficient α is defined by the following equation:

In nuclear engineering, prompt criticality describes a nuclear fission event in which criticality is achieved with prompt neutrons alone and does not rely on delayed neutrons. As a result, prompt supercriticality causes a much more rapid growth in the rate of energy release than other forms of criticality. Nuclear weapons are based on prompt criticality, while most nuclear reactors rely on delayed neutrons to achieve criticality.

A basis point is one hundredth of a percent or equivalently one percent of one percent or one ten thousandth. A very rarely used term, permyriad, means parts per ten thousand, differing in meaning only in that basis points are normally used to express differences in parts per ten thousand. Figures are commonly quoted in basis points in finance, especially in fixed income markets.

A percentage point or percent point is the unit for the arithmetic difference of two percentages. For example, moving up from 40 percent to 44 percent is an increase of 4 percentage points, but a 10-percent increase in the quantity being measured. In literature, the unit is usually either written out, or abbreviated as pp or p.p. to avoid ambiguity. After the first occurrence, some writers abbreviate by using just "point" or "points".

The nuclear cross section of a nucleus is used to describe the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction. The standard unit for measuring a nuclear cross section is the barn, which is equal to 10−28 m², 10−24 cm² or 100 fm². Cross sections can be measured for all possible interaction processes together, in which case they are called total cross sections, or for specific processes, distinguishing elastic scattering and inelastic scattering; of the latter, amongst neutron cross sections the absorption cross sections are of particular interest.

Nuclear reactor physics is the field of physics that studies and deals with the applied study and engineering applications of chain reaction to induce a controlled rate of fission in a nuclear reactor for the production of energy. Most nuclear reactors use a chain reaction to induce a controlled rate of nuclear fission in fissile material, releasing both energy and free neutrons. A reactor consists of an assembly of nuclear fuel, usually surrounded by a neutron moderator such as regular water, heavy water, graphite, or zirconium hydride, and fitted with mechanisms such as control rods that control the rate of the reaction.

Gravity (alcoholic beverage)

Gravity, in the context of fermenting alcoholic beverages, refers to the specific gravity, or relative density compared to water, of the wort or must at various stages in the fermentation. The concept is used in the brewing and wine-making industries. Specific gravity is measured by a hydrometer, refractometer, pycnometer or oscillating U-tube electronic meter.

Critical heat flux (CHF) describes the thermal limit of a phenomenon where a phase change occurs during heating, which suddenly decreases the efficiency of heat transfer, thus causing localised overheating of the heating surface.

In physics and quantum chemistry, specifically density functional theory, the Kohn–Sham equation is the non-interacting Schrödinger equation of a fictitious system of non-interacting particles that generate the same density as any given system of interacting particles. The Kohn–Sham equation is defined by a local effective (fictitious) external potential in which the non-interacting particles move, typically denoted as vs(r) or veff(r), called the Kohn–Sham potential. As the particles in the Kohn–Sham system are non-interacting fermions, the Kohn–Sham wavefunction is a single Slater determinant constructed from a set of orbitals that are the lowest-energy solutions to

Hayashi track

The Hayashi track is a luminosity–temperature relationship obeyed by infant stars of less than 3 M in the pre-main-sequence phase of stellar evolution. It is named after Japanese astrophysicist Chushiro Hayashi. On the Hertzsprung–Russell diagram, which plots luminosity against temperature, the track is a nearly vertical curve. After a protostar ends its phase of rapid contraction and becomes a T Tauri star, it is extremely luminous. The star continues to contract, but much more slowly. While slowly contracting, the star follows the Hayashi track downwards, becoming several times less luminous but staying at roughly the same surface temperature, until either a radiative zone develops, at which point the star starts following the Henyey track, or nuclear fusion begins, marking its entry onto the main sequence.

In chemistry, the mass fraction of a substance within a mixture is the ratio of the mass of that substance to the total mass of the mixture. Expressed as a formula, the mass fraction is:

In chemistry, the mass concentrationρi is defined as the mass of a constituent mi divided by the volume of the mixture V.

The Inhour equation used in nuclear reactor kinetics to relate reactivity and the reactor period. Inhour is short for "inverse hour" and is defined as the reactivity which will make the stable reactor period equal to 1 hour. Reactivity is more commonly expressed as per cent millie (pcm) of Δk/k or dollars.

Pulsed nuclear thermal rocket

A pulsed nuclear thermal rocket is a type of nuclear thermal rocket (NTR) concept developed at the Polytechnic University of Catalonia, Spain, and presented at the 2016 AIAA/SAE/ASEE Propulsion Conference for thrust and specific impulse (Isp) amplification in a conventional nuclear thermal rocket.

The removal of heat from nuclear reactors is an essential step in the generation of energy from nuclear reactions. In nuclear engineering there are a number of empirical or semi-empirical relations used for quantifying the process of removing heat from a nuclear reactor core so that the reactor operates in the projected temperature interval that depends on the materials used in the construction of the reactor. The effectiveness of removal of heat from the reactor core depends on many factors, including the cooling agents used and the type of reactor. Common coolers for nuclear reactors include: heavy water, the first alkaline metals, lead or lead-based alloys, and .