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Dose rate dependence on successful radiation treatment of cultural heritage objects

The application of radiation treatment for preservation of cultural heritage (CH) has been growing recently. To be able to widen the use of radiation treatment, the influence of radiation on many materials that constitute CH have been studied recently, as well as on common bioburden found on CH. Although it is well known that the dose rate plays an important role in radiation physics and chemistry, when it comes to studying the dose rate effect on radiation treatment of CH the influence of dose rate on both material and bioburden has been only sporadically investigated. Still, it is important to know if a dose rate can influence the efficient elimination of bioburden, or increase changes in the material during radiation treatment. The purpose of this study is to asses influence of the dose rate on the antifungal effect, as well as on the potential material changes, i.e. degradation. Different materials commonly found on CH were irradiated to different dose rates, paper, binders and leather, in order to study the effect dose rate has on the materials. Since cellulose, the main constituent of paper-made objects of CH, is a favorable substrate for fungal growth, the microbiological studies have been performed on paper. Acid-free Verge paper has been inoculated with Cladosporium. To observe the antifungal effect microbiological analysis of irradiated samples was conducted immediately after irradiation and after different intervals of time. To assess the effects of irradiation on materials FTIR and colorimetry were performed. The results have shown that the dose rate plays an important yet generally neglected role in the efficacy of the radiation treatment in some particular cases. In order to reduce fungal burden to an acceptable level the initial contamination needs to be considered since antifungal effectiveness of radiation treatment depends on radiation resistance of fungal species and size of contaminant inoculum. If the contamination is high the applied dose needs to be adjusted considering that the dose needed to reduce the molds to an acceptable level significantly increased for the low dose rates. This research was cofounded by IAEA Coordinated Research Project (CRP 2077) “Disinfection and Consolidation of Archived Materials and Cultural Heritage Artefacts by Radiation Processing Techniques”.

ionizing radiation, cultural heritage treatment, radiation effects

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