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At least 343 records · Page 19Linked to original sources
PubMed2001

A radiation incident involving detachment of a cobalt-60 industrial radiography source and its management.

A radiation incident took place inside an open-top radiography enclosure involving an Amertest-676 exposure device containing a cobalt-60 source of activity 2.15 TBq. The exposure device was being checked after receipt of a fresh source. The source assembly having been projected out could not be brought back into the exposure device. After thorough planning, the situation was brought under control by driving the disengaged source assembly into the exposure device. During the incident, the maximum individual whole body dose was 3.1 mSv.

Accidents, Occupational↗
PubMed2002

The use of passive environmental TLDs in the operation of the Spanish early warning network 'REVIRA'.

As required by different international agreements, the regulatory body in Spain (Consejo de Seguridad Nuclear) implemented in 1992 a national automatic network (REVIRA) that continuously monitors radiation levels in order to give early warning of incidents having potential transboundary implications. The detector for environmental gamma-radiation dose rate is an active instrument based on a Geiger-Müller counter. However, the use of passive environmental dosemeters provides an additional low-cost dose estimate with an independent centralised calibration and even better basic features than active instruments. Since 1999, all 25 REVIRA stations have been monitored with passive TL environmental dosemeters based on LiF:Mg,Cu,P and operated according to the procedures established at Ciemat. This paper presents the obtained results and the further analysis considering differences in aspects such as photon energy response, inherent background or response to cosmic rays. The benefits of the use of passive environmental dosemeters in early warning networks are discussed.

Air Pollution, Radioactive↗
PubMed2002

The use of the Monte Carlo simulation technique for the design of an H*(10) dosemeter based on TLD-100.

The thermoluminescence (TL) detector material LiF:Mg,Ti (TLD-100) and appropriate filter materials were combined in order to design a passive dosemeter measuring the operational quantity ambient dose equivalent, H*(10), for monitoring low-dose external photon radiation fields. Using the Monte Carlo simulation technique, optimisations of energy dependent conversion coefficients from air kerma free-in-air compared to ICRU and ISO proposed values. h*K(10), were performed by varying dosemeter detector positioning. geometrical arrangements, and filter materials. Deviations smaller than 5% compared to h*K(10) between 30 keV and 2.5 MeV of primary photon energies were achieved by a dosemeter design consisting of a 15 microm Sn metal layer and a 5 mm PMMA layer surrounding the LiF detector. Subsequently performed free-air verification experiments carried out in well defined standard photon radiation fields showed an obviously TL-specific effect. An underestimation up to -15% of the modelled data at low photon energies was observed.

Air Pollutants, Radioactive↗
PubMed1999

Analysis of electret ion chamber radon detector response to 222Rn and interference from background gamma radiation.

Environmental radon (222Rn) monitors that incorporate electret detectors are confounded by background gamma radiation, which may cause the electret to discharge by as much as 7.5 volts per mR. Although background gamma corrections were formerly made by multiplying the known background gamma exposure rate with a constant conversion factor, this research demonstrates that doing so introduces an error ranging up to about 20%, especially in high gamma background areas. A new, more accurate method of background gamma correction has been developed that uses an average, voltage-dependent discharge factor, Dgamma (V Kg C(-1)). This factor and its coefficients were experimentally determined by separately exposing groups of electret radon detectors to photons from 60Co and 137Cs. Statistical analysis shows that Dgamma is independent of the orientation of the electret during irradiation but that some dependency on dose rate or energy of the irradiating photons may be expected. The discharge of the electret due only to gamma irradiation, Vgamma is determined by multiplying the total integrated gamma exposure by Dgamma. The discharge of the electret during a radon measurement can then be corrected for background gamma radiation by subtracting Vgamma from the total discharge of the electret resulting in a net discharge due solely to radon. A new equation has also been developed in this study for the radon discharge factor, D(Rn)(V m3 Bq(-1) s(-1)), that is entirely consistent with the gamma discharge factor and was thoroughly evaluated by exposing the electret radon detectors to known concentrations of radon.

Air Pollution, Radioactive↗
PubMed2006

Management of spent sealed radioactive sources in Turkey.

Spent radioactive sources (SRS) have been generated from industrial applications, research, and medicine in Turkey. In this study, management of SRS (Co, Cs) at Cekmece Waste Processing and Storage Facility (CWPSF) is described. Eleven Cs sources (total 851 GBq) and four Co sources (total 27.75 GBq) that had been used as levels and density gauges were conditioned. Reinforced metal drums (200 L in volume) and cement matrix were used for conditioning of these sources. In this way, greater confinement was achieved for long-term storage. Maximum dose rates at the surface of the conditioned waste package were determined. In addition to information about conditioning stages of the sources, various calculations that have been done for shielding are presented. Surface dose rates of the waste packages were 1.60 mSv h for Cs and 1.63 mSv h for Co. Measurements of the final waste packages were presented to fulfill the requirements (<2 mSv h) of transportation according to regulations for the safe transport of radioactive material.

Cesium Radioisotopes↗