12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > The design and calibration of a phantom for dep...
View graph of relations

« Back

The design and calibration of a phantom for depth profiling measurements of entrained radioactivity in silica-based media

Research output: Contribution to journalJournal article

Published

Journal publication date2011
JournalNuclear Engineering and Design
Journal number2
Volume241
Number of pages7
Pages526-532
Original languageEnglish

Abstract

The development of a phantom which replicates the effect of concrete on radioactivity entrained within it is described. The phantom was designed as a basis on which methods can be developed to measure the depth of radioactive contamination in the concrete of defunct nuclear facilities. In particular, this apparatus has been used to validate a differential attenuation method for the profiling of radioactive contamination at depth. Entrained radioactive contamination is a significant issue in defunct nuclear facilities where in situ, non-destructive assay of radioactive waste arisings is a routine requirement.

The phantom comprises a polymethylmethacrylate structure filled with high-purity silica-sand which, for the purposes of the application, is an effective analogue of fully-hydrated concrete paste. A void was created within the silica sand which incorporates a sliding mechanism for the insertion of a radioactive source to a required depth. The sealed source represents the entrained radioactivity in the phantom but is also specifiable, removable and poses no long-term contamination risk beyond the expected life of the apparatus. The remainder of the void either side of the source is filled with silica-sand to complete the homogeneity of the phantom. The void was situated near the front of the phantom constructed at a 5.14° angle with respect to the front scanning surface; thus the apparent depth within the silica-sand can be varied by changing the position of the source along the phantom's void.

The steps taken to develop the concrete phantom are described. The design has been validated with a set of radiation transport simulations affording comparison with an exemplar of the concrete found used in nuclear facilities. Some initial results from measurements taken with the phantom and a caesium-137 γ-radiation source in combination with a sodium iodide radiation detector are provided. These measurements are used to validate the differential attenuation method and compared with data from previous measurement attempts with concrete slices.