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Index/Radiation protection/RPR-31

RPR-31

Number of half-value layers

n = log2(1/B). How many HVLs a transmission B requires.

Reading speed
ShieldingHVL count

Governing equation

n=log⁡2(1/B)n=\log_2(1/B)

B∈[1×10−7,1]B \in \left[1\times 10^{-7}, 1\right]

where

B
Transmission B (—)
n
Half-value layers (—)

The figure, part by part

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RPR-31 · gauge
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①

Governing law — red

n=log⁡2(1/B)n=\log_2(1/B)

B∈[1×10−7,1]B \in \left[1\times 10^{-7}, 1\right]

B=1×10−7B = 1\times 10^{-7}n=23.25n = 23.25

②

Domain of the variable — blue

Bmin⁡=1×10−7,Bmax⁡=1B_{\min} = 1\times 10^{-7},\quad B_{\max} = 1

B∈[1×10−7,1]B \in \left[1\times 10^{-7}, 1\right]

B=1×10−7B = 1\times 10^{-7}B=1×10−7B = 1\times 10^{-7}

③

Response curve — green

n=log⁡2(1/B)n=\log_2(1/B)

B∈[1×10−7,1]B \in \left[1\times 10^{-7}, 1\right]

B=1×10−7B = 1\times 10^{-7}n=23.25n = 23.25

④

Rate of change — amber

dndB\frac{\mathrm{d}n}{\mathrm{d}B}

B∈[1×10−7,1]B \in \left[1\times 10^{-7}, 1\right]

B=0.006B = 0.006n′=−1346.8n^{\prime} = -1346.8

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-31 — Number of half-value layers) is the form associated with HVL count. Working symbols: BB →\rightarrow nn. Ten HVLs is 10^{−3} transmission (because 2^{10} ≈ 10^3). Pair with HVL of the actual material and energy.

Purpose

Purpose: compute nn from BB in Radiation protection via n=log⁡2(1/B)n=\log_2(1/B) n = log2(1/B). How many HVLs a transmission B requires. 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 B=0.010 —B = 0.010\,\mathrm{—}, the governing relation n=log⁡2(1/B)n=\log_2(1/B) yields n=6.644 —n = 6.644\,\mathrm{—}. A required B counted in doublings of attenuation. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Outputs

  • Half-value layers n6.644 —
Reading speed

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RPR-31 · gauge
00:0 / 00:08

Narration of this film

A required B counted in doublings of attenuation.

Ten HVLs is 10^{−3} transmission (because 2^{10} ≈ 10^3). Pair with HVL of the actual material and energy.

Reading speed

Watch on YouTube