Evaluation of calibration factors of digital survey meters in a secondary standard dosimetry laboratory.

The calibration of radiological survey meters is an important consideration in achieving standardisation of doses. This provides traceability for field instruments to an International System of Units. Seventy-one digital survey meters were calibrated by the substitution method in a 137Cs beam in a secondary standard dosimetry laboratory using a PTW spherical ionisation chamber coupled to a Physikalisch-Technische-Werkstaetten (PTW) UNIDOS Electrometer. The calibration factors determined ranged from 0.59 to 1.98. Thirty-six pieces of equipment have their calibration factors within 0.9-1.1. A total of 36% of the survey meters recorded calibration factors corresponding to a percentage deviation above 20% whilst 64% fell within 20% deviations from the true value. The best value of a calibration factor obtained in this work was 1.00 from two survey meters. The errors due to survey meters being out of calibration can usually be corrected by frequent recalibration.

ASSESSMENT OF RADIOFREQUENCY RADIATION WITHIN THE VICINITY OF SOME GSM BASE STATIONS IN GHANA: A FOLLOW-UP.

A follow-up of radiofrequency (RF) electromagnetic radiation safety survey at public access points had been carried out in 46 towns on 76 Global Systems for Mobile Communications and Universal Mobile Telecommunication System cell sites in two major cities in Ghana. The core objective was to determine the RF field levels in residential areas, schools and marketplaces and compare the measured results with the guidelines set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Measurements were made with calibrated log-periodic antenna coupled with a spectrum analyzer. The results obtained varied from 0.0008 to 182 mW m -2, which generally shows compliance with the ICNIRP reference levels. The highest value was 1.39 % of the reference.

Radiation dose assessment for occupationally exposed workers in Malawi.

Background: The objective of this study was to assess individual doses received by radiographers, and the scattered radiation dose rate reaching the control panel in X-ray departments of three hospitals in Malawi, in-order to compare them against the internationally recommended limits. Methods: Themoluminescent Dosimeters were issued to fifteen (15) radiographers to record their dose for a month. Dose rate measurements were recorded using survey meters. Results: Average monthly dose for workers was 0.247mSv. Average ambient dose rate values were 0.39µSv/hr for Mtengo wa Nthenga Hospital, 5.03µSv/hr for Bwaila Hospital and 4µSv/hr for Kamuzu Central Hospital. Conclusions: Dose levels are below the limits recommended by the International Commission on Radiological Protection (ICRP).