RPR-13

Skyshine snapshot

Ḣ = k Ḣ0 B Ω / d². Roof scatter raining down outside the vault.

Reading speed

ScatterNCRP 151 skyshine

Governing equation

\dot H=k\dot H_0 B\Omega/d^{2}

$d \in \left[3, 80\right]$

where

\dot H_0: Isocentre rate toward roof (mSv/h)
B: Roof transmission (—)
\Omega: Roof solid angle (sr)
d: Horizontal distance (m)
k: Skyshine constant k (m²)
\dot H: Skyshine dose rate (µSv/h)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

\dot H=k\dot H_0 B\Omega/d^{2}

$d \in \left[3, 80\right]$

$d = 3$ $\dot H = 22.22$

Along the curve

②

Domain of the variable — blue

d_{\min} = 3,\quad d_{\max} = 80

$d \in \left[3, 80\right]$

$d = 3$ $d = 3$

Along the curve

③

Response curve — green

\dot H=k\dot H_0 B\Omega/d^{2}

$d \in \left[3, 80\right]$

$d = 3$ $\dot H = 22.22$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}\dot H}{\mathrm{d}d}

$d \in \left[3, 80\right]$

$d = 3.484$ $\dot H^{\prime} = -9.833$

Along the curve

Lecture brief

Historical brief

Inverse-square, half-value layer, ICRP weighting and ALARA are the protection craft since the 1920s commissions. The lab computes transmission, equivalent dose and a shielding snapshot. This sheet (RPR-13 — Skyshine snapshot) is the form associated with NCRP 151 skyshine. Working symbols: $\dot H_0$ , $B$ , $\Omega$ , $d$ , $k$ $\rightarrow$ $\dot H$ . A thin roof and a large solid angle Ω make skyshine. McGinley's k ≈ 0.025 m² is a first look; NCRP 151 is geometry-richer.

Purpose

Purpose: compute

\dot H

from

\dot H_0

B

\Omega

d

k

in Radiation protection via

\dot H=k\dot H_0 B\Omega/d^{2}

Ḣ = k Ḣ0 B Ω / d². Roof scatter raining down outside the vault. Use it when a real radiation protection question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

\dot H_0 = 200.000\,\mathrm{mSv/h}

B = 0.050\,\mathrm{—}

\Omega = 0.800\,\mathrm{sr}

d = 15.000\,\mathrm{m}

k = 0.025\,\mathrm{m^{2}}

, the governing relation

\dot H=k\dot H_0 B\Omega/d^{2}

yields

\dot H = 0.889\,\mathrm{\mu Sv/h}

. A roof, a sky hemisphere, a point in the car park. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Isocentre rate toward roof \dot H_0200 mSv/hRoof transmission B0.05 —Roof solid angle \Omega0.8 srHorizontal distance d15 mSkyshine constant k k0.025 m²

Outputs

Skyshine dose rate \dot H0.889 µSv/h

Reading speed

Watch on YouTube

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Narration of this film

A roof, a sky hemisphere, a point in the car park.

A thin roof and a large solid angle Ω make skyshine. McGinley's k ≈ 0.025 m² is a first look; NCRP 151 is geometry-richer.

Reading speed

Watch on YouTube