## **Shielding, corrected** * **Buildup factors now use ANSI/ANS-6.4.3** for each shield material — lead, tungsten, tin, copper, iron, aluminium, concrete, and water — across **15 keV–15 MeV**, applied according to the standard. The previous factors stopped at 0.5 MeV and substituted data between materials. **Dose behind thick lead was therefore underestimated:** the Cs-137 dose behind 10 cm of lead was about half the corrected value, and the 5 cm result was about 25% low. For a low-energy source in water, the result was up to 2× too low. * **New: optional air attenuation and scatter.** Air between the source and detector can now be included using the corresponding standard data. This is particularly useful near radiography boundaries. It is **off by default**, since published dose constants generally assume vacuum. ## **Neutron activation, corrected** * **Fast-neutron reaction rates now use the IAEA IRDFF-II library**, averaged over the spectrum of the selected source: reactor fission neutrons, Am-Be, or D-D/D-T generators. For Am-Be, the previous Fe-54(n,p) result was **3.4× too low**; for a reactor spectrum, O-16(n,p) was **43% too low**. * **New fast-flux monitors:** Ni-58(n,p)Co-58, Ti-46(n,p)Sc-46, S-32(n,p)P-32, and Cu-63(n,α)Co-60, plus a **D-T neutron-generator source**. **Every calculator and dataset remains free.**

## 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.**

## Nuclear Toolkit Pro Export any calculation as a dated PDF containing the inputs, assumptions, results, and data-source citations, with space for a signature. It is a report you can file—not just a screenshot. Exported reports are also saved in history on your device, so you can show exactly what was calculated and which assumptions were applied. **$2.99/month or $14.99/year.** If you’ve already supported the app, Pro is included—thank you. ## Everything else remains free All eleven calculators, 3,383 nuclides, 661 metastable isomers, gamma-emission lines, neutron cross sections for 291 isotopes, photon attenuation data, saved scenarios, and image export. Still offline. No account. No ads. Your inputs are never collected. ## Fixes * Fixed an issue where the app could stop responding to taps after opening a nuclide and switching tabs quickly. An invisible overlay could be left behind. * Made pinch-to-zoom on the Chart of Nuclides smoother. The axis rulers now track the grid throughout the gesture instead of snapping into place at the end. * Updated the information and atom icons so they match the tab bar’s text styling instead of rendering as full-colour emoji.

> **PDF calculation reports** > > Any calculation can now be exported as a dated PDF carrying its inputs, the > assumptions applied, the results, and the data-source citations — with space > for a signature. Available in the Dose, Decay, Decay Chain, MDA, Activation, > Shielding, Mixture and Xenon calculators. > > Exported reports are kept in a history on your device, so you can show later > what was calculated and what it assumed, and re-export any of them. Nothing is > uploaded. > > **Saved scenarios** > > Every calculator now remembers named setups — a source and geometry, a > detector configuration, an irradiation. They persist between sessions. > > **Clearer isomer data** > > Metastable isomers now label their excitation energy as a level energy and > show the principal emitted gamma beside it. These are different quantities: > Ag-110m sits at a 117.6 keV level but emits a 657.8 keV photon, and the > emitted energy is the one that matters for detection and shielding. > > **Chart of Nuclides** > > The zoom readout now follows the actual zoom and reads "Fit" for the opening > view. Mass numbers appear when zooming by wheel or pinch. Axis rulers stay > locked to the chart during a pinch instead of snapping at the end. Phones open > at a legible scale rather than fitting all 179 × 118 cells into a smear. > > **Also** > > Exported files are now named readably, e.g. > `gamma-dose-rate-assessment-2026-09-17-14-30.pdf`. > > Every calculator and dataset in the app remains free.

> **Metastable isomers** > > All 661 metastable isomers are now in the app, sourced from the IAEA Live > Chart of Nuclides (ENSDF evaluated levels) — the same provenance as the > 3,383 ground states already there. > > • Selectable in the Decay and Decay Chain calculators, so Tc-99m, Ba-137m, > In-113m, Ag-110m and Am-242m can finally be used directly > • Each has its own decay chain. A pure-IT isomer like Tc-99m sits one step in > front of its ground state (Tc-99m → Tc-99 → Ru-99); a branching one like > Ag-110m keeps both paths and their reconvergence > • Tap any nuclide in the chart to see its isomers, their excitation energies, > half-lives and decay branches > > **Neutron cross sections** > > Thermal (2200 m/s) cross sections and resonance integrals now appear on the > nuclide detail sheet, covering 40 isotopes — the common activation targets > plus the absorbers, reactor poisons and fissile nuclides. > > Coverage is partial and the app says so rather than implying otherwise. There > is no freely available machine-readable source spanning the whole chart, and > every value carries its citation. > > **Also in this release** > > • Chart of Nuclides axis rulers stay accurate at every zoom level > • Assorted layout and typography fixes > > Every feature in the app remains free, offline and account-free.

Enabled payment for the Support Development section and made several minor improvements to the UI. You can find The Support Development from the tab on the very bottom-right. It is together with the Feedback button. Not hard to find in less than 5 mins.