Nuclear Toolkit

## Nuclear Toolkit — Calculation and Recordkeeping Updates Every calculation in Nuclear Toolkit has been re-checked against independent methods. The following results and behaviors have been corrected or expanded. ### Calculation updates **Dose & Shielding — short-lived progeny** Pb-212, Bi-212, Ba-140, Mo-99, Np-237, Zr-95, Ce-144, Ra-228, Pb-214, and Ba-131 were previously available only as standalone sources. For an aged source, however, their progeny can contribute most of the gamma dose, causing the standalone result to read several times too low. Each now has a **“+progeny”** entry. Selecting the standalone nuclide explicitly indicates that progeny are not included. **Ra-224 (+progeny)** was also corrected after being found to be about 15% low. **Reactor period** The stable period calculation now uses all six delayed-neutron groups. The previous single-group approximation could produce periods up to three times too long near prompt critical and gave about **−13 s** after a scram instead of the correct **−80 s**. **Decay chains** Activities now follow every branch of the decay chain. When a nuclide branches, the unshown branch is identified—for example, **Bi-212 sends 35.94% to Tl-208**. A chain that is cut short now states that explicitly. **Neutron activation** Epithermal flux now uses the standard **k₀ convention (per unit lethargy)**, and the input field identifies this convention. Resonance-rich targets, including gold, previously read about **20–40% too low**. **Cross sections** Cross-section data now cover **298 isotopes**, including **Th-232, Pa-231, Np-237, Am-243, and Ra-226**. **Shielding assumptions** The shielding calculations now state where the buildup treatment is approximate for energies below **0.5 MeV**. ### Nuclear Toolkit Pro — Calculation Records Every exported calculation is now stored as a numbered record, such as **NT-2026-0001**. Each record includes: * Case or project * Preparer * Reviewer * Organization * User notes * Signature lines * The exact versions of the nuclear data used Records can be exported as **PDF or CSV**. Calculation history is searchable on the device, and any previous record can be re-exported. ### Other updates * The **Mixture** tab now explains how elements with no stable isotope are handled. * Percentages near 100% no longer appear in scientific notation such as **“1.0e+2 %”**. * The subscription screen now links directly to the **Terms of Use** and **Privacy Policy**. **All calculators and datasets remain free.**