Varieties of Thermoluminescent Dosimeters Used in the Personnel Dosimetry Laboratory in Radiation Protection Institute in Ghana

Base on the routine care and maintenance of the Harshaw TLD 6600 Plus Reader, this publication will emphasize on the nominal value and tolerance parameters of the Harshaw TLD 6600 Plus Reader and the readout will be compared to the standard criteria, by analysing the records of quality control QC readouts and the co efficient of variation parameters respectively. The parameters of the electronic QC which include the nominal value and tolerance parameters have been monitored and also compared to those of standard criteria. Moreover, the readout results which were obtained from the Personnel Dosimetry Laboratory show that the Harshaw TLD 6600 Plus Reader was working efficiently. Hence it can be used in the Personnel Dosimetry Laboratory. This study serves as an integral component which contributes to the comprehensive routine measurements that are carried out daily in performing the electronic QC in the Personnel Dosimetry laboratory in Ghana Atomic Energy Commission.

ing of the TLD cards result in a glow curve whose area is proportional to the dose.
The Finger ring is made of durable low density polypropylene plastic and is adjustable to fit finger sizes from 16 to 28 mm in diameter. It is available in a variety of colours to identify different body areas. While the Chest badge is used for estimation of the whole body dose, worn at the chest level. The Wrist badge has strap to be worn around wrist. It is used to estimate the dose to hands and the forearms when they are likely to be selectively exposed [3].
The dosimeters are also produced in certified factories which produced a controlled material quality (Dosimetry) to meet their application purposes.
Some of such factories include is;

Introduction
In personnel monitoring service, neutron monitoring and environmental monitoring, the use of TLD cards comes in different forms depending on the type of work the Technologist or Radiographer is carried out or performing and the type of radioactive source he is working on. The TLD cards have various parameters such as Basically, the thermoluminescent consist of a four element doped with Li, Mg, Ti and F for measuring doses in personnel monitoring [2]. The heat- Figure 1a: Picture showing finger ring that are worn by occupationally exposed workers who work with radioactive source.   The purpose of the holder is to serve as a protector. That is it protects the TL material from mechanical damage and crystal damage. Another function of the holder is to allow various filters to be placed in front of the TL crystals. This filters serves as energy dependency which permits the filters to filter out unwanted particles ( Figure 2, Figure 3, Figure 4 and

TLD Card Holders
The TLD Card Holders are made up of various colours, which are in-cooperated with filters and they are made up of durable, tissue-equivalent, ABS plastic, and is casketed and sealed to retain the card in a light and moisture excluding environment. The Holder protects the cards from environmental damage and retains the filtration media which attenuate the various radiation types to protect selective entrapment in the TL material. This difference in radiation absorption allows determination of shallow, deep and lens of the eyes doses as well as some energy discrimination.
When the TL material is placed in a holder and sent to the field, when it is placed in the holder, the package is known as thermoluminescent dosimeter.

Who Should Use
The TLD badges to be used only by persons as approved by Radiation Protection Institute directly working with radiation sources such as X-ray units, radioisotopes etc. The dark room technicians, sweepers security guards etc. need not normally be provide with. In case of doubt kindly write to Radiation Protection Institute.
It may be noted that TLD badge is used to measure the radiation dose to which the user is exposed. It does not protect the user from the radiation.

Precaution Measures Needed When Using the TLD Dosimeters
A TLD -600 chip, 0.38 mm thick, with 300 mg/cm 2 ABS plastic filtration measures lens of the eye and neutron dose.
The principle is based on the phenomenon of thermos luminescence, the emission of light when certain materials are heated after exposure to radiations. It gives very reliable results since no fading is observed under extreme climatic conditions such ambient temperature and humidity.
Personnel doses, received by Occupationally Exposed Workers are determined from measurement made from the Thermoluminescent Dosimeters which was worn by the Occupationally Exposed Workers respectively. This type of monitoring is known as Personnel Monitoring.  One TLD badge should be worn compulsorily at the chest level. If a lead rubber apron is used, (for example": In diagnostic X-ray departments) TLD badge should be worn under the lead apron at the chest level.
The dose recorded by the TLD badge worn at chest level represents the whole body dose equivalent.
Persons who working with industrial radiogra-phy cameras should compulsorily use wrist badges in addition to chest badges [8].

Preparation of Reports (OEW'S)
Choose any Clients (Occupationally Exposed Work's) that have been monitored to the History forms.
• Do not share your TLD Dosimeter with anyone.
• Always leave your TLD Dosimeter badge in the control room when not in use.

Where to Wear the TLD Dosimeters
In special cases, depending upon the nature of radiation work, if the doses to hands and forearms are expected to significantly higher than at the chest level, additional wrist badges may be procedure and used [7]. Examples of such categories are persons handling radioisotopes from close distances and radiologists/doctors doing the special investigations such as cardiac catheterization, angiography's etc. The Dosimeters ID with exteres ( * ) were identified as BAD DOSIMETERS [5,6]. These include: Dosimeter ID * 0700818, * 0700704, * 0701085 and * 0700965.