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For First Responders · Neutron Transport

Neutron Transport for a smoke detector

Built for first responders planning or training for real incidents. Run fast what-if scenarios for response planning and training — no software to install in the field. Simulate a smoke detector live below — adjust the inputs and watch it respond, right in your browser.

Neutron TransportLive

random walk & moderation

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Mean free path (px)

Neutrons do not travel straight — they random-walk through matter, scattering every mean free path and losing energy at each collision. This moderation slows fast neutrons to thermal speeds where they fission efficiently. A short mean free path (dense material) keeps them inside; a long one lets them leak out, which is why reactor size and geometry set criticality.

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Data Inspector

Mean free path30 px

Escaped0 / 40

Leakage0%

Governing equation

λ = \frac{1}{Σ} = 30 px, Σ = 0.0333 px^{- 1}

Reading this result: A moderate mean free path balances moderation against leakage — enough scattering to thermalize neutrons, but geometry still governs whether the core goes critical.

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Frequently asked questions

Is this good for first responders?: Yes — this version of "Neutron Transport for a smoke detector" is framed for first responders planning or training for real incidents. Run fast what-if scenarios for response planning and training — no software to install in the field.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.