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Occupational exposures in conventional and interventional radiology were investigated over a period of 10 years for all radiation workers. The statistical analysis carried out on the refined data showed that the average annual effective doses in conventional and interventional radiology were 0.28 and 0.59 mSv for measurably exposed workers and 0.18 and 0.52 mSv for all monitored workers in 2014. More than 99.9 and 82.8% of radiation workers in conventional and interventional radiology received annual doses less than the public dose limit (1 mSv) in 2014. Comparing the occupational dose levels of different countries (including Iran) in conventional as well as interventional radiology showed a poor comparability among them. Regarding the doses above the investigation level, the analysis showed that majority of them were due to improper use of personal dosimeters (false doses) and only 0.01 and 0.12% of the dose records actually crossed the level in conventional and interventional radiology in 2014.

Estimation of terrestrial external radiation is essential for assessment of public exposure to natural radiation. During national survey of natural radionuclide in soil in Iran, 979 soil samples were collected from different locations, in the same time ambient dose equivalent rate was measured by a scintillator detector. In this work, terrestrial radiation was estimated by direct measurement of ambient dose equivalent rate of background radiation. The response of dose measuring instrument to cosmic radiation at ground level was measured and other components were discussed and estimated. For verification, terrestrial radiation derived from this method was compared with those calculated from activity concentration of natural radionuclides in soil. The averages of ambient dose equivalent rate derived from activity concentration of by natural radionuclide in soil and from direct measurement are 55.07 and 62.57 nSv/h, respectively. The source of statistical and systematic uncertainties are introduced and discussed.

This report presents status of external and internal dose assessment of workers and introducing the structure of National Dose Registry System of Iran (NDRSI). As well as types of individual dosemeters in use, techniques for internal dose assessment are presented. Results obtained from the International Atomic Energy Agency intercomparison programme on measurement of personal dose equivalent H(p) (10) and consistency of the measured doses with the delivered doses are shown. Also, implementation of dosimetry standards, establishment of quality management system, authorisation and approval procedure of dosimetry service providers are discussed.

The neural network method has been used for the unfolding of neutron spectra in neutron spectrometry by Bonner spheres. A back propagation algorithm was used for training of neural networks. 4 mm x 4 mm bare LiI (Eu) and in a polyethylene sphere set: 2, 3, 4, 5, 6, 7, 8, 10, 12, 18 inch diameter have been used for unfolding of neutron spectra. Neural networks were trained by 199 sets of neutron spectra, which were subdivided into 6, 8, 10, 12, 15 and 20 energy bins and for each of them an appropriate neural network was designed and trained. The validation was performed by the 21 sets of neutron spectra. A neural network with 10 energy bins which had a mean value of error of 6% for dose equivalent estimation of spectra in the validation set showed the best results. The obtained results show that neural networks can be applied as an effective method for unfolding neutron spectra especially when the main target is neutron dosimetry.

Despite well-developed Regulatory Authority systems for radiation protection, there are some concerns about lost-controlled and poorly controlled radioactive sources owing to abundance and dispersion of the users. This survey covers the current situation of the categories 3 through 5 of radioactive sources (based on the categorisation of the IAEA) in non-medical applications in Iran. The investigation performed on a selected group of non-medical users of radioactive sources in different provinces of Iran. Findings show that unauthorised supply and legacy sources in addition to abandonment of sources under regulatory control are the main reasons for lost-controlled sources. Considering the possibility of increasing poorly controlled sources which can lead to increase in the number of lost-controlled sources, further developments are needed in national regulatory control as well as international cooperation and discipline in this regard.

This paper discusses an accident, which occurred in one of the radiation application centres in Iran, follow-up investigations as well as lessons learnt. In January 2004 the Regulatory Authority was informed through a university radiation protection officer of an accident regarding orphan sources. Investigations revealed that one Am-Be and three (137)Cs sources in the container were subject to extensive heat due to burning of the container and melting of the paraffin content of the container; consequently, sources were stuck to the side wall of the container, but they were still undamaged and no radioactive leaking had occurred. Further investigations showed that the container had been given to the above mentioned centre a long time before by a foreign well-logging company without notifying the Regulatory Authority. Follow-up measurements and assessments indicated that the collective effective dose due to the accident is unlikely to be more than 21 mSv; consequently, no severe deterministic effect to individuals was expected. The findings showed that the main reasons for the accident were as follows: (1) violation of obligation under radiation protection regulations by the owner of the sources; (2) leaving the sources in an improper storage condition; (3) unauthorised access to the radiation sources at the owner centre; and (4) lack of an integrated national registration system in the Regulatory Authority.