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This paper describes the evaluation of an inexpensive, commercially available 35 mm transparency slide scanner as a potential alternative scanning device for GafChromic HD-810 radiochromic dye film. Besides its low cost, the principal advantages of this type of scanner are high spatial resolution and high speed (a typical scan taking less than 1 min). With broad-band illumination the useful dose range using grey-scale imaging of GafChromic HD-810 is limited to about 50-800 Gy. By using the colour-scale imaging capability of the scanner we have been able to achieve a significant extension covering a similar range (15-2000 Gy) to that attainable using monochromatic illumination. The short-term reproducibility of the system is good, with a coefficient of variation of doses estimated from repeat scanning of uniformly exposed calibration films of less than 2%. Long-term stability is ensured by the scanning of a manufacturer-supplied test slide. The slide scanner system has been used in the determination of depth dose distributions from a model 'hot particle' source containing 106Ru/Rh. GafChromic dye film stacks irradiated by the source were read out on both the slide scanner and a conventional Joyce Loebl MDM6 scanning stage microdensitometer. The overall agreement between the dose estimates provided by the two systems was within 10%.

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The assessment of radiological hazard due to external and internal indoor exposure was investigated for 26 raw granites collected from different granite quarries in Ranyah (KSA). The activity concentrations of 226 Ra, 232 Th and 40 K were measured by highresolution gamma spectrometry. Four granites were classified as "anomalous" due to their relatively high radioactivity. The averages and ranges of their activity concentrations were 667 (305-1120), 320 (161-491) and 586 (282-893) Bq•kg −1 , respectively. The corresponding ones for all remaining 22 granites were 45 (18-77), 39 (16-73) and 1178 (954-1531) Bq•kg −1 , respectively. In accordance with new European Basic Safety Standards (BSS) directives requiring a uniform reference level for indoor external exposure to gamma rays of 1 mSv•y −1 , all 22 granites may be used as bulk or ornamental building materials without any restrictions. Three anomalous granites should be subjected to control to be used as bulk materials. One anomalous granite was categorized as hazardous having an activity concentration index higher than 6. All four anomalous granites exceeded the level of newly adopted reference level of 300 Bq•m −3 for radon indoor exposure in case of poor ventilation. Two of them exceeded even for adequate ventilation.

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