DESIGN AND CONSTRUCTION OF RADIATION ALARM DEVICE
DESIGN AND CONSTRUCTION OF RADIATION ALARM DEVICE
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Date
2014-03-04
Authors
ADAMU, HAMISU ABUBAKAR
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Abstract
There is a defined level of ionizing radiation (effective dose of 50mSv
in any single year) that radiation workers are allowed to be exposed to,
according to the International Committee on Radiation Protection (I.C.R.P)
proposal which is duly adopted by International Atomic Energy Agency.
Gas detectors are commonly used for radiation monitoring because of
their ease of operation. In principle, a gas detector can be operated as an
Ionization chamber, a Proportional counter, or a Geiger- Mueller tube,
depending on the level of high voltage bias supply it is subjected to. Geiger
– Mueller detectors are preferred for radiation monitoring because of their
ability to detect nearly all kinds of ionizing radiation and they provide a very
strong signal that a pre-amplifier is not necessary.
This work has utilized the characteristics of G-M tubes to design and
construct a Radiation alarm device capable of detecting unsafe radiation
level in its vicinity. The device is intended for both indoor and outdoor use.
This has therefore necessitated the use of a 9 volts alkaline battery for the
device. Complementary Metal Oxide Semiconductor (CMOS) integrated
circuit(IC) low power consumption and its ability to operate satisfactorily on
a wide range of supply voltage made it a choice for this project. High
efficiency performance of Switched Mode Power Supplies (SMPS) has been
harnessed to provide high voltage (HV) bias for the G-M tube. In order to
further decrease the power consumption of the unit, the high voltage circuit
was gated such that it operates for a very short period, and a buffer capacitor
used to supply the tube continuously during the inactive period of the high
voltage circuit.
The radiation alarm device developed is capable of alerting personnel
once exposed to radiation dose of 27µSv/hour (Twenty seven microSeivert
per hour) or higher. This threshold was found to be the maximum allowable
radiation a personnel is allowed to be exposed to. Beside the cost advantage
that the Radiation Alarm Device has over existing similar devices, it is also
difficult to acquire ionizing radiation related instruments due to restrictions
imposed on them globally. The cost of the device is put at about twenty
seven thousand naira (N27,000), a price much less than the price for GM-90
Geiger Counter Radiation Detector, a product of Black cat system, whose
price is three hundred and fifty dollars ($350).
Description
A thesis submitted to the postgraduate school of the Ahmadu Bello
University, Zaria, IN PARTIAL FULFILMENT OF THE RECRUITMENT
FOR THE AWARD OF MASTER OF SCIENCE (MSC) ELECTRICAL
ENGINEERING.
Keywords
DESIGN,, CONSTRUCTION,, RADIATION,, ALARM,, DEVICE,