Shielding Calculator

Broad-beam TVL/HVL attenuation · X-ray & gamma · RSSJA internal scoping tool

INTERNAL USE ONLY

Required barrier thickness

x = TVL × log₁₀(P₀·T / P) x = thickness · TVL = tenth-value layer · P₀ = unshielded dose rate · P = target dose rate · T = occupancy factor

Radiation source

Barrier material

Unshielded dose rate P₀

Target dose rate P

Dose-rate unit

Occupancy factor T NCRP 147

TVL / HVL override optional — leave blank to use the table

Value

Type

Unit

Required thickness

—

Attenuation needed

—

Dose rate behind a barrier

P = P₀ × 10^{−x / TVL} transmission B = 10^−x/TVL · attenuation factor = 1/B

Radiation source

Barrier material

Barrier thickness

Thickness unit

Unshielded dose rate P₀

Dose-rate unit

Occupancy factor T NCRP 147

TVL / HVL override optional — leave blank to use the table

Value

Type

Unit

Dose rate behind barrier

—

Transmission factor B

—

Tenth-value layers (TVL) & half-value layers (HVL)

Broad-beam, high-attenuation (equilibrium) values. HVL = TVL ÷ 3.322. “—” = no published value in the cited table for that combination.

Source	Lead TVL	Lead HVL	Concrete TVL	Concrete HVL	Steel TVL	Steel HVL

X-ray values: NRC “Principles of Radiation Shielding”, Table 7.1 (NCRP data), broad-beam conditions.
Gamma values: IAEA Manual on Shielded Enclosures (Practical Radiation Safety Manual PRSM-2, Rev. 1, 1996).
Tc-99m TVL: computed as 3.32 × HVL (0.2 mm Pb) — approximate at low energy.

⚠ Internal Use Only — scoping tool, not a shielding design. TVLs are broad-beam equilibrium values; narrow-beam geometry, buildup, skyshine, leakage/scatter components, and occupancy/workload factors are not modelled. Final shielding for any real installation must be designed and verified by a qualified expert per NCRP 147 (medical X-ray) / NCRP 151 (megavoltage) or the applicable HSRA requirements. Verify tabulated values against the cited references before use.