Universal Decay Calculator - HELP

(last updated 19 Jun 2024)

Contents:

• Introduction · Nuclide Input · Output Parameters · Bibliography

Introduction

Initial activities of up to 16 nuclide series can be defined in the Nuclide Input table. For a time given in the Output Parameters table, the resulting activities of the nuclides given, plus those of any decay products growing in are calculated.
The calculator moreover assesses the radiation hazard from the nuclides by calculating the air kerma (kinetic energy released per unit mass: the kinetic energy of charged particles liberated by photon and neutron interactions per unit mass), whereby the nuclides are treated as a point source.
The database contains a total of 1252 nuclides.

The calculator performs a complete decay analysis for the nuclides entered and all their decay products, according to [Bateman 1910]; minor nuclides are listed at the end.
Note: For the air kerma calculations, the air kerma coefficient K_air,δ for a hypothetical point source from [ICRP 2008] is used. It includes gamma rays, characteristic x rays, and inner bremsstrahlung, but does not necessarily cover all radiations from a real source.

The results are presented in numerical form in the Results table for the end time specified, and optionally, in an Output Chart showing the total series activities for each series specified, or individual nuclide activities, vs. time. The output chart type can be chosen as a line chart, a stacked area chart, or an animated bar chart.
If charts are enabled, computing time may increase. Please be aware that in line charts, a nuclide may hide one or more others.
The contents of the numerical result field can be marked and copied to the clipboard for further use.

The contents of the database for any nuclide can be checked with the "Query nuclide database" button (shows half-life, specific activity, possible parent nuclides, and decay products with branching ratios and decay type).
Note that only alpha and beta decays are listed: in addition, each decay emits gamma radiation.

See special instructions for offline use of this calculator.

For decay calculations of uranium, the Uranium Decay Calculator offers more options, such as a variety of uranium compounds found in the uranium mining and nuclear fuel industry, and the inclusion of decay energy results.

For comparison of the activities of the various wastes produced during nuclear fuel production and use, see the Nuclear Fuel Chain Waste Activity Calculator.

Nuclide Input

• 1 g U(nat) pure: 1 gram of pure natural uranium, no decay products present
• 1 g U(nat) equil.: 1 gram of natural uranium in secular equilibrium with its decay products
• 1 g Th(nat) pure: 1 gram of pure natural thorium *), no decay products present
• 1 g Th(nat) equil.: 1 gram of natural thorium *) in secular equilibrium with its decay products
• 1 tHM spent fuel (33 GWd/t, at unload): 1 metric tonne of heavy metal contained in spent fuel from a light water reactor after burnup of 33 GWd/t, at time of unload (short-lived nuclides omitted)
• 1 tHM spent fuel (33 GWd/t, 5 y after unload): 1 metric tonne of heavy metal contained in spent fuel from a light water reactor after burnup of 33 GWd/t, 5 years after unload
• HLW from reproc. of 1 tHM spent fuel (33 GWd/t, reproc. 5 y after unload): High-Level Waste from reprocessing of 1 metric tonne of heavy metal contained in spent fuel from a light water reactor after burnup of 33 GWd/t, reprocessed 5 years after unload
• 1 g U(rep) (init. enr. 3.5%, 39 GWd/t, 5 y delay): 1 gram of reprocessed uranium, initial enrichment 3.5 weight-% U-235, after burnup of 39 GWd/t in light water reactor separated from spent fuel 5 years after unload
• 1 t tailings from ore grade 0.1% U at 90% extraction: 1 metric tonne of uranium mill tailings generated from processing of an ore with an ore grade of 0.1% U with an extraction efficiency of 90%
• 1 g U(nat-enr) (3.5 wt-% U-235): 1 gram of enriched natural uranium, enriched to 3.5 weight-% U-235
• 1 g U(rep-enr) (init. enr. 3.5%, 39 GWd/t, 5 y delay): 1 gram of re-enriched reprocessed uranium, re-enriched to equivalent of initial enrichment 3.5 weight-% U-235, after burnup of 39 GWd/t in light water reactor separated from spent fuel 5 years after unload
• 1 g U(nat-dep) (0.2 wt-% U-235): 1 gram of depleted uranium with 0.2 weight-% U-235, generated from enrichment of natural uranium to 3.5 weight-% U-235
• 1 g U(rep-dep) (0.2 wt-% U-235, init. enr. 3.5%, 39 GWd/t, 5 y delay): 1 gram of depleted uranium with 0.2 weight-% U-235, generated from re-enrichment of reprocessed uranium to equivalent of initial enrichment of 3.5 weight-% U-235, after burnup of 39 GWd/t in light water reactor separated from spent fuel 5 years after unload
• heels from 12,500 kg UF6(nat) in 48Y cylinder: heels (non-volatile residue) left from unloading of a Type 48Y cylinder by heating, initially holding 12,500 kg natural UF₆
• heels from 2,277 kg UF6(nat-enr) (3.5wt-% U-235) in 30B cylinder: heels (non-volatile residue) left from unloading of a Type 30B cylinder by heating, initally holding 2,277 kg of enriched (3.5wt-% U-235) UF₆

Activity Unit

the selected unit is used for all activity entries in this table

Series Name

Enter nuclide name using the notation  Th-232 , for example.
Enter here the first member (for which an activity is to be specified) of a decay series, or a nuclide which is not a member of a series.
The name is checked with the database immediately on entry. If the nuclide is not found, the available nuclides resp. elements are listed.
Upon entry of a valid nuclide name, all decay products are listed in the "Nuclide Name" pick list; minor nuclides are listed at the end.

Nuclide Name

Select nuclide within the series, for which an activity value is to be entered or viewed.

Initial Activity

enter number for initial activity of the nuclide selected in the "Nuclide Name" pick list.
(uses Activity Unit selected at top of table)

Pure

check, in case only the pure nuclide shown in "Series Name" is present initially. The activities of all decay products are set to zero.

Equil.

check, in case the decay products of the nuclide shown in "Series Name" initially are present in secular equilibrium. The activites of all decay products are initialized to the equilibrium state.

Indiv.

check, in case individual entries are to be made for the initial activities of each nuclide in the series.
If only single nuclides of the series differ from the "Pure" or "Equil." state, select the appropriate button first, and then select "Indiv." and change the activity of the desired nuclide(s).

Note: it is possible, though not advisable, to explicitly specify a nuclide as a series which also is a member of the decay series of another nuclide entered. In this case, all calculations are performed independently, leading to multiple listing of the nuclide and any decay products in the result.

Output Parameters

Time

Enter numbers for Start, End, and List time and select appropriate time unit.
The numerical results displayed in the Results field are for the specified List Time, while the charts cover the whole time period between Start and End time.
Note: For List Time = 0, the numerical result shows all initial activities.
Note: In case of a linear time axis, the Start time 0 is used, independent of the entry made.

Chart Type

Select option.

Chart Data

Select option.
If "air kerma" is chosen, select air kerma unit and enter air kerma point source distance [m]

Chart Detail

Select options.
If "skip minor nuclides" is selected, then the chart legend shows only those nuclides that are visible in the chart. The number of minor nuclides can further be reduced by reducing the "Decades on log. Y axis" value, if "log. Y axis" is chosen for line charts.

Chart Axes

Select option.

Bibliography

[Bateman 1910] Harry Bateman: Solution of a system of differential equations occurring in the theory of radioactive transformations , in: Proceedings of the Cambridge Philosophical Society, Mathematical and physical sciences. Cambridge [etc.] Cambridge Philosophical Society. v. 15 (1908-10): Pages 423-427

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