Table of nuclides

This is a table of all nuclides with masses between 228 and 260, and atomic numbers between 90 (thorium) and 100 (fermium). The word "nuclide" refers to a nucleus with a specified number of protons and neutrons. This is to be contrasted with the word "isotope", which refers to a nucleus of a specific element that has a specified number of neutrons, and the word "element" which refers to a nucleus with a specified bumber of protons but an unspecified number of neutrons. The word "isotope" is often erroneously used in place of "nuclide", but these are in fact slightly different concepts. If you speak a specific nucleus without context, such as "Plutonium 239", it would properly be called a nuclide. However, if it is already established that you are talking about plutonium in particular, then "Plutonium 239" can be called an isotope. You can also say something like "Plutonium 239 is an isotope of plutonium" even without previous context. In other words, if you are speaking of a specific element, the word "isotope" is to be used, and if you are merely speaking of nuclei in general, the word "nuclide" is to be used instead.

Ok, enough on definitions. What does this table show? Each cell contains a variety of data for a specific nuclide. In the center is the atomic symbol for the element that the nuclide is an isotope of, as well as the mass of the nuclide in atomic mass units. In the lower left corner is the half life of the element, which ranges from as little as four microseconds to as much as 14 billion years. This half life also determines the background color, starting at purple for very short lived nuclides and going around the rainbow through blue, green, yellow, and finally to red as the half lives grow progressively longer. In the lower right corner is the decay mode for that nuclide. If it decays in significant proportion by multiple modes, all relevant modes are shown with percentages to indicate the branching ratio, if that data is available. In the two upper corners is neutronics data, which concerns the interaction of the nuclide with thermal neutrons.

I represent the neutronics data in two different formats. I call the first one "absolute format" and the second one "relative format", but these are really just random names that I came up with to distinguish the two. These names do not have any greater meaning than that. To see the data presented in each format, simply select the corresponding radio button and the table will automatically adjust itself.

Absolute format

In the upper left corner is the number of prompt neutrons released per fission event, in neutrons, and below it is the number of delayed neutrons released per fission event, in millineutrons (thousandths of a neutron). These numbers are fractional because it is a statistical average. Any given fission event will always release a whole number of prompt and delayed neutrons, although the vast majority of fission events do not release any delayed neutrons at all.

In the upper right corner is the neutron capture cross-section, and below it is the fission cross-section, both in barns.

Relative format

In the upper left corner is the number of total neutrons (prompt and delayed) released per neutron absorption event, in neutrons, and below it is the percentage of released neutrons that are delayed neutrons.

In the upper right corner is the neutron absorption cross-section, in barns, and below it is the percentage chance that the neutron absorption event will cause the nucleus to fission.

Notable nuclear isomers

Protactinium 234m is the exclusive decay product (99.8% of the time, at least) of thorium 234, making it a part of the uranium 238 decay chain in place of protactinium 234 (the other 0.2%), which is not produced in appreciable quantity in the decay chain of uranium 238. Due to its very short half-life, it was named "brevium" upon discovery.

Americium 242m is produced about 10% of the time from neutron capture by americium 241. Due to its long half-life, large cross section, high chance of fission, and large number of neutrons released per fission, it is a nearly ideal fuel, but cannot be made use of due to the near impossibility of separating it from the americium 241 that it must be produced from, and the low chance that any given neutron capture by americium 241 will actually produce americium 242m. The alternative, americium 242, has similarly favorable properties, although a somewhat smaller cross-section, but decays far too fast to be used.

Colors

• Bright purple - A half life less than one second.
• Dark purple - A half life between one second and one minute.
• Dark blue - A half life between one minute and one hour.
• Sky blue - A half life between one hour and one day.
• Cyan - A half life between one day and thirty days.
• Turquoise - A half life between thirty days and one year.
• Green - A half life between one year and ten years.
• Chartreuse - A half life between ten years and one hundred years.
• Yellow - A half life between one hundred years and one thousand years.
• Orange - A half life between one thousand years and ten thousand years.
• Red - A half life beyond ten thousand years.
• White - No data available.

Terminology

• Nuclear isomer - A nucleus in an excited state that has a half life long enough to be distinguished as a distinct kind of nucleus.
• Neutron absorption - When a nucleus absorbs a free neutron that is passing by.
• Neutron capture - When a nucleus successfully captures an absorbed neutron causing it to increase in mass by one atomic mass unit.
• Fission - When a nucleus splits into two unequal halves of random size upon absorption of a neutron, typically releasing a few neutrons in the process. This produces a great deal of energy. It can also happen spontaneously as a decay mode of certain nuclei.
• Cross-section - Roughly, the probability that a passing neutron will interact with the nucleus in the specified way. It is measured in units of area, typically in barns.
• Neutron absorption cross-section - The sum of the neutron capture cross-section and the fission cross-section.
• Neutron capture cross-section - The cross-section for neutron capture.
• Fission cross-section - The cross-section for neutron induced fission.
• Alpha decay - A decay mode where a nucleus emits a cluster of two neutrons and two protons, which is called an alpha particle.
• Beta decay - A decay mode where a nucleus emits an electron or a positron, which are called beta particles.
• Beta minus decay - A decay mode where a nucleus emits an electron, converting a single neutron into a proton in the process.
• Beta plus decay - A decay mode where a nucleus emits a positron, converting a single proton into a neutron in the process.
• Electron capture - A decay mode where a nucleus captures an electron, converting a single proton into a neutron in the process.
• Spontaneous fission - A decay mode where a nucleus spontaneously fissions without the absorption of a neutron to initiate the process.
• Isomeric transition - A decay mode where a nuclear isomer decays into the ground state.

Units

• Barn - A unit of area equal to 100 square femtometers.
• Femtometer - A unit of distance equal to one quadrillionth of a meter, or equivalently, one trillionth of a millimeter.

Symbols

• α - The greek letter alpha, and also the symbol for alpha decay.
• β - The greek letter beta, and also the symbol for beta decay
• β^- - The symbol for beta minus decay.
• ^mβ^- - The symbol for beta minus decay where the produced nucleus is a nuclear isomer.
• β⁺ - The symbol for beta plus decay.
• EC - The symbol for electron capture.
• SF - The symbol for spontaneous fission.
• IT - The symbol for isomeric transition.
• b - The symbol for a barn as a unit of area.
• n - The symbol for a neutron.
• mn - The symbol for a millineutron, or a thousandth of a neutron.
• μs - The symbol for a microsecond, or a millionth of a second.
• ms - The symbol for a millisecond, or a thousandth of a second.
• s - The symbol for a second.
• m - The symbol for a minute.
• h - The symbol for an hour.
• d - The symbol for a day.
• y - The symbol for a year.
• ky - The symbol for a kiloyear, or one thousand years.
• My - The symbol for a megayear, or one million years.
• Gy - The symbol for a gigayear, or one billion years.

Data

All half-life and decay data was acquired from the various wikipedia pages for the isotopes of each element, e.g. Isotopes of Thorium

All neutronics data was acquired from wwwndc.jaea.go.jp. More specifically, it was acquired from URLs such as https://wwwndc.jaea.go.jp/cgi-bin/Tab80WWW.cgi?lib=J40&iso=U235 where the element name and mass "U235" at the end of the URL was replaced with whatever element I needed data for. For the nuclear isomers, I used "Pa234m" and "Am242m". When collecting cross-section data I used the "Maxwellian Average" column, and when collecting prompt and delayed neutron emission data I used the "0.0253-eV" column.