Radionuclide Decay Chains

This webpage serves as a comprehensive tool for generating illustrations depicting radionuclide decay chains as defined in the ICRP 2008-database. Additionally, it offers the functionality to compute and visualize the temporal progression of radionuclide decay and ingrowth based on user-defined initial conditions. Users can access radionuclide-specific settings by right-clicking on a particular radionuclide within the chart.

The time evolution of radionuclide-specific characteristics can be displayed in a range of units including activity (measured in Becquerels, Bq), quantity (measured in moles), radiotoxicity upon ingestion (measured in Sieverts, Sv), external radiotoxicity (measured in Sv/(s m3)), and energy emission rate (measured in megaelectronvolts per second, MeV/s). Furthermore, users can view the total energy emission rate or analyze it separately according to alpha emissions, electron emissions (including beta emissions), or photon emissions.

Conversion coefficients utilized to convert radionuclide activity (measured in Bq) to radiotoxicity upon ingestion (measured in Sv) for adults are sourced from the ICRP 1995 guidelines. Similarly, conversion coefficients employed to convert radionuclide activity (measured in Bq) to external radiotoxicity (measured in Sv/(s m3)) in an infinite soil environment are drawn from the EPA 2019 recommendations.

The ICRP 2008-database comprises comprehensive data on 1252 radionuclides across 97 elements, encompassing details such as half-lives, decay chains, and the yields and energies of emitted radiations resulting from nuclear transformations. The selection of nuclides for inclusion in the database was contingent on their half-life exceeding 1 minute or if they were formed as a byproduct in the nuclear transformation of a designated radionuclide. Notably, N-16, with a half-life of 7.13 seconds, was included primarily for historical significance. It is imperative that the underlying nuclear physics data be sufficiently robust to enable meaningful computations of radiation yields and energies.

The database contains compiled information for 922 radionuclides with half-lives surpassing 10 minutes, as well as 330 radionuclides with half-lives less than 10 minutes. Data pertaining to the 118 chemical elements within the periodic table are predominantly sourced from the National Center for Biotechnology Information as of 2023.

Glossary

Activity
The activity of a radionuclide expresses the number of transformations over a certain time interval. Its unit is 1 Becquerel (Bq), which represents an activity equal to one conversion per second.

Alpha decay
In alpha decay, the nucleus of an atom of atomic number Z and mass number A emits an alpha particle (⁴He nucleus) to form an atom of atomic number Z - 2 and mass number A - 4.

Auger transition
The filling of a vacancy in an inner electron shell of an atom, e.g. as created in electron capture, is accompanied by the emission of an electron from the outer shell, an Auger electron.

Beta-minus decay
In beta-minus decay, the nucleus of an atom of atomic number Z and mass number A emits a negative electron (β^-) and an antineutrino (v) to form an atom of atomic number Z + 1 and mass number A.

Beta-plus decay
In beta-plus decay, the nucleus of an atom of atomic number Z and mass number A emits a positive electron (β⁺, positron) and a neutrino (v) to form an atom of atomic number Z - 1 and mass number A.

Branching fraction
Branching fraction is the fraction of the nuclear transformations of the radionuclide that forms a particular daughter nucleus.

Coster-Kronig (CK) transition
CK transition is an Auger transition in which the atomic shell vacancy is filled by an electron from a higher subshell of the same shell.

Inner bremsstrahlung
Inner bremsstrahlung is a continuous electromagnetic radiation produced by the sudden change of nuclear charge which occurs in beta-plus, beta-minus, or electron-capture decay. This radiation is not included here because of its low energy and low yield.

Electron-capture decay
In electron-capture decay, the nucleus of an atom of atomic number Z and mass number A captures an atomic electron and emits a neutrino (v) to form an atom of atomic number Z - 1 and mass number A.

Half-life (T_1/2)
The half-life of a radionuclide is the interval required for its activity to decay to half of its initial value. The half-life is related to the decay constant λ as T_1/2 = ln(2)/λ and to the mean life τ as τ = T_1/2/ln(2).

Gamma ray
Gamma-rays are electromagnetic radiations (photons) emitted by the nucleus in transition from a high energy state to a lower energy state.

Isomeric transition decay
A nucleus in an excited energy state of an atom of atomic number Z and mass number A can transition to a lower energy state by emission of a gamma ray, or eject an orbital electron with the excess energy. No change in atomic and mass numbers occurs; the parent and daughter nuclei are isomers. Isomers of energy above the ground state are identified by appending 'm', 'n', 'p', or 'q' to the mass number.

Isomers
Nuclei of the same atomic number Z and mass number A but with a different energy state and different physical half-life. Isomers of energy above the ground state are identified by appending 'm', 'n', 'p', or 'q' to the mass number.

Internal conversion electron
An internal conversion electron is an orbital electron ejected from the atom as a result of the energy difference between states of the nucleus being transferred directly to a bound atomic electron. This process is a form of isomeric decay.

Mole
The mole (symbol mol) is the unit of measurement for amount of substance, a quantity proportional to the number of elementary entities of a substance. One mole contains exactly 6.02214076×10²³ elementary entities.

Nuclear transformation
Nuclear transformation is the occurrence of the decay process(es) that spontaneously transform(s) an atom from one state to another. It is often referred to as 'decay' and its SI unit is the becquerel.

Spontaneous fission
Spontaneous fission is a decay mechanism resulting in splitting of the nucleus into lighter nuclei, referred to as 'fission fragments', with the emission of neutrons.

Transition
The individual process by which a nucleus is spontaneously transformed to another energy state.

X ray
The filling of a vacancy in an inner electron shell of an atom, e.g. created in electron capture, may be accompanied by the emission of an x-ray photon.

References

ICRP, 2008. Nuclear Decay Data for Dosimetric Calculations. ICRP Publication 107. Ann. ICRP 38 (3). PDF
ICRP, 1995. Age-dependent Doses to the Members of the Public from Intake of Radionuclides - Part 5 Compilation of Ingestion and Inhalation Coefficients. ICRP Publication 72. Ann. ICRP 26 (1). PDF
EPA, 2019. External Exposure to Radionuclides in Air, Water and Soil. Federal Guidance Report No. 15. EPA-402-R-19-002, U.S. Environmental Protection Agency, Washington DC. PDF
National Center for Biotechnology Information, 2023. Periodic Table of Elements. Retrieved September 20, 2023 from https://pubchem.ncbi.nlm.nih.gov/periodic-table/