A method in non-destructive testing for lead shielding exceeding 25 kg/m2 using 18F

TL;DR

This paper presents a new non-destructive testing method using a Fluorine-18 source to verify thick lead shielding in radiation protection.

Contribution

A reproducible field-ready NDT method for lead barriers exceeding 25 kg/m2 using 18F and validated through simulations and measurements.

Findings

The method models transmission through lead up to 302.7 kg/m2 using Monte Carlo simulations.

Empirical validation showed agreement with simulations up to 162.4 kg/m2 at 38.1 cm source-to-detector distance.

SDDs above 23 cm provide sufficient narrow beam conditions for field NDT.

Abstract

Non-Destructive Testing (NDT) is a commonly used technique for barrier verification within radiation protection, ensuring compliance with national standards and state regulations. There are currently limited published methods in NDT for lead shielding above 25 kg/m2, and thus this research aimed to develop a reproducible method to aid in ‘in the field’ NDT for lead barriers exceeding 25 kg/m2 using a Fluorine-18 (18F) source. Due to the fast decay of 18F, the data generated within this research was compiled from Monte Carlo (MC) simulations using the PENELOPE engine, and the PENGEOM geometry system to model the proposed empirical setup. The model predicted the Transmission Factor (TF) through area densities (thickness) of lead attenuators up to 302.7 kg/m2, with results validated by empirical measurements using a Source-to-Detector Distance (SDD) of 38.1 ± 0.05 cm and 52.7 ± 0.05 cm. However, the study was limited by the chosen activity of 18F at approximately 180 MBq, where the simulated TF curves demonstrated correspondence of data up to and including area densities of 162.4 kg/m2 using a 38.1 ± 0.05 cm SDD, and 138.0 kg/m2 with a 52.7 ± 0.05 cm SDD. Beyond these thicknesses, the empirical transmission curves deviated from simulated curves due to measurable transmissions becoming significantly reduced. This research demonstrated that using SDDs above 23 cm would provide sufficient near narrow beam conditions with the proposed experimental configuration for in-the-field NDT. The research aimed to develop an equation and method for NDT using a 18F source for lead barriers greater than 25 kg/m2, with transmission data to be made available upon request to the author.

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