Radionuclide Decay Chains
This webpage serves as a comprehensive tool for generating illustrations depicting radionuclide decay chains as defined in the ICRP 2008-database, or in a release of the Evaluated Nuclear Structure Data File (ENSDF) chosen under Database above the chain. 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 a radionuclide in the chart, or by tapping one on a touch screen.
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.
The descriptive data on the chemical elements (origin of the name, atomic weight, density, melting and boiling points) are adapted from Wikipedia\'s List of chemical elements and the element articles, available under the CC BY-SA 4.0 licence.
Another database: ENSDF
The Database menu above the chain chooses the data the chains are drawn from. ICRP Publication 107 is built into the page. The other choices are releases of the Evaluated Nuclear Structure Data File (ENSDF), the evaluated nuclear structure and decay data for every known nuclide, kept by the National Nuclear Data Center (NNDC) at Brookhaven: the releases installed on this site, those opened in this browser, and every release in the NNDC archive back to 2004. They are the releases the Chart of Nuclides offers, and a release opened on either page is offered on both. NNDC’s server does not let other sites read its files, so a release from the archive is downloaded first and then opened with Open ENSDF…, or dropped on the page; it is read in your browser in a few seconds, and nothing is uploaded. Forget stops keeping an opened release in this browser.
With ENSDF, the element list holds every radioactive state the database gives a half-life for: the ground states and the isomers, named m, or m1, m2 … where a nuclide has several, as on the Chart of Nuclides. The decay modes and branching fractions are those of the adopted data sets, and which isomer of a daughter a branch feeds is worked out from the decay data sets. Two settings beside the menu choose what a chain holds: the smallest branch, and the shortest half-life. By default every branch is drawn, and the isomers that live less than a second are left out. A member that is left out decays as fast as it is made: the arrows go straight on to where it decays, an arrow that jumps over one says via it, and what it gives off is counted with the member that feeds it. On an arrow, ≤ marks a share the evaluators give only as a limit, ≥ one that may be more because part of the way has no percentage, ? a branch with no percentage at all, which carries nothing, and * a branch ENSDF does not give but the Q-values leave open. A member whose half-life the database does not give is shown with a ? and is held, not decayed.
The energies given off per decay come from the ENSDF decay data sets, as the Chart of Nuclides works them out; the X-rays and Auger electrons after electron capture, which ENSDF does not list, are estimated from the K-shell binding energy. The radiotoxicities use the ICRP 1995 and EPA 2019 coefficients whatever the database. A state takes those of the same nuclide in ICRP Publication 107, an isomer those of the ICRP 107 isomer with its half-life; a member with none counts as zero, as it does with ICRP 107.
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 (T1/2)
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 T1/2 = ln(2)/λ and to the mean life τ as τ = T1/2/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/
National Nuclear Data Center.
Evaluated Nuclear Structure Data File (ENSDF). Brookhaven National Laboratory, on behalf of the Nuclear Structure and Decay Data network. The release in use is named in the Database menu.