Calculators
Each page explains one calculation — the formula, a worked example, the assumptions and the sources — and opens the matching calculator in the app already set up. The numbers are computed by the app’s own physics code.
Decay
- Tc-99m decay calculator
- Tc-99m half-life 6.0072 h: remaining activity at any time, back-decay to a draw time, and a decay table from 740 MBq (20 mCi), computed from ENSDF data.
- Radioactive decay calculator
- Activity after any time for 3,383 nuclides and 661 isomers from IAEA data: the decay law, a half-life table for common sources, and worked examples from a calibration date.
- Decay chain calculator
- Daughter ingrowth and decay chains solved with the Bateman equations: Rn-222 ingrowth from Ra-226, Ba-140 to La-140 transient equilibrium, and when each kind of equilibrium applies.
Dose and shielding
- Cs-137 dose rate and shielding
- Cs-137 gamma dose rate: 0.326 R/h per curie at 1 m, H*(10) per GBq, a distance table and half-value layers in lead, steel, concrete and water with buildup.
- Co-60 shielding
- Co-60 half- and tenth-value layers in lead, tungsten, steel, concrete and water, narrow and broad beam, and the lead and concrete needed to reach a target dose rate.
- Ir-192 radiography
- Ir-192 gamma constant 0.462 R/h per Ci at 1 m; dose rate from a 100 Ci radiography source against distance, and HVLs in tungsten and lead.
- Pb-212 dose rate
- Pb-212 dose rate with its Bi-212 and Tl-208 progeny at transient equilibrium: 8× the parent alone, with the lead thickness each needs.
Counting
- MDA calculator
- Minimum detectable activity from background counts, count time, efficiency and emission probability: Currie L_C and L_D, MDA in Bq and pCi, and MDC per kilogram, with a worked Cs-137 example.
Reactor and fuel cycle
- Neutron activation calculator
- Activation product activity from thermal and epithermal flux, irradiation and cooling time: the Høgdahl rate equation, cross sections with citations, and worked gold-foil and cobalt examples.
- SWU calculator
- Separative work units and natural uranium feed per kilogram of enriched product, from 3 % LEU to 19.75 % HALEU, with the value function and the effect of tails assay.
- Xe-135 poisoning
- Xenon-135 equilibrium reactivity against flux, the iodine pit after shutdown (peak time and depth), and the one-group model behind them, from ENSDF half-lives and textbook yields.
- Reactor period calculator
- Stable reactor period against reactivity in dollars from the six-group inhour equation with Keepin U-235 delayed-neutron data, including the −80 s limit after a scram.