Personnel dosimeter refers to monitoring of individuals who are exposed to radiation during the course of the work.

To avoid the excessive exposure, appropriate and efficient radiation monitoring device is needed.

Radiation exposure must be monitored for both personal safety and regulatory purpose,

Many instruments are used for individual monitoring.

The instruments used for recording the dose equivalents received by individuals working with radiation are referred to as personal dosimeters (or individual dosimeters).

Monitor and control the individual dose.

Maintain lifetime cumulative dose record.

Assurances that dose is within permissible limit.

It is useful for detecting changes in radiation levels in the workplace and to provide information in case of accidental exposure.

In India, country wide monitoring service is offered by BhaBha Atomic research centre (BARC) Mumbai.

Instantaneous response

Accurately measure the dose equivalent from all forms of ionizing radiation with energy from KeV- MeV

Small, lightweight, rugged, inexpensive, easy to use.

Unaffected by environmental condition (heat, humidity, pressure)

There are different types of personnel monitoring devices ex- film badge, TLD, OSLD, pocket dosimeter.

A film badge dosimeter or film badge is a personal monitoring cumulative radiation dose due to ionizing radiation.

film badges are the cheapest and most common monitoring device.

It is used to measure the individual dose from x-rays, beta particle, gamma radiation, thermal neutrons on the basis of different filters (windows).

It was developed by Ernest O Wollan whilst working on the Manhattan project during 1942.

Film badge is made up of

1.Photographic film

2.Filters

3.Badge holder

Photographic film is a sheet of transparent plastic film base coated on one/both side with a gelatin emulsion containing small light sensitive silver halide crystals.

Film size is 4*3 cm wrapped inside by a light tight polythene or paper cover

There are two film in the badge one is slow and another is fast

Supply of film is for a period of one calendar month(4 weeks)

• Without any filter
• It detects alpha particles
• Due to minimum penetration power of
• alpha particles no metallic filter is used

• Filter is made of plastic
• Light white colour
• It detects (beta)particles
• Thickness of filter :1mm

• Filter is made of thin copper
• Green in colour
• It detects low energy x-rays
• Thickness of filter :0.15mm

• Filter is made of thick copper
• Pink  in colour
• It detects high energy x-rays
• Thickness of filter :1mm

• Filter is made of lead
• Black in colour
• It detects gamma rays
• Thickness of filter :1mm

All the filters are 1mm thick, except thin copper which is 0.15mm thick

Film is sealed with a plastic cover which contain the name, ID no or duration.

The filters allow the radiation to penetrate and thus permit the energy to be stored and estimated.

The BARC processed the film, and measure the optical densities by densitometer’

When radiation exposes the film after passing through the filters it cause formation of latent image on the film.

Latent image has regions of different density under the different filters due to their different penetration power

After each months (4 weeks) it is returned to the agency where the film is processed and the optical density under different filters is measured by a densitometer.

Dose under each filter is evaluated using the standard calibration curve

After processing the film badge monthly dose report is sent to the institution This report contains current month’s report and up to date cumulative dose of the current year.

Dose is reported in mSv.

The type of holder are

1.Chest holder

2.Wrist holder

3.Head holder

Minimum dose that can be detected by film badge is 0.2 mSv

Range of film badge is 10 KeV to 2MeV

This badge should be kept in cool, dry and control area

The badge is typically worn on the outside of clothing, around the chest or torso to represent dose to the “whole body”.

Additional dosimeters can be worn to assess dose to extremities or in radiation fields that vary considerably depending on orientation of the body to the source.

It gives permanent record.

Wide exposure range

Independent of dose rate

Type of radiation and energy can be evaluated

Least expensive device

Small, light weight ,easy to handle

High sensitivity to light, pressure and chemicals

Fades at high temperature and humidity

Limited shelf life (one month)

Only records exposure where it’s worn.

DO;

Wear your dosimeter correctly

Check your exposure dose

Report any unusual radiation incident to your RSO

DON’T

Don’t share your film badge with anyone.

Don’t open the film badge  till the end of service period.

Don’t leave the badge in radiation area, or in chemical hazardous place .