Half Layer Value of Wood and Aluminum Industrial Hygiene – Lab Report Example

To estimate To estimate half layer value of wood and Aluminum Industrial Hygiene Lab (SFTY 315L) Lab. lab sessionIntroduction (Theory)
Ionization radiation can be basically defined as an activity whereby the number of nucleus undergoing disintegration in a given quantity of material per unit of time. It can be defined using a Becquerel which is one disintegration per unit second. This can be related to a curie which is the measure of the rate at which a radioactive material usually emits particles in such a manner that 1C=3.7X1010 Bq. Ionization radiation normally occurs in two major forms; waves and particles. Examples of radiations include: radio waves, heat waves, and infrared, x-rays, gamma rays and visible light (Glenn, 1999). What define the difference between these radiations is their different frequencies. Only those radiations that are high on the electromagnetic spectrum are ionizing in nature. Visible light and radio waves normally display wave like characteristics while visible while interacting with matter. Particulate radiation on the other hand consists of both atomic and subatomic particles which usually carry energy as kinetic energy. Gamma rays are normally electrically neutral and do not interact with atomic electrons. Exposure to the radiations can be hazardous in nature resulting into health problems to people (William, 1999). Measures should be taken protect the people interacting with these radiations. Exposure limits are provided for in the general industry and are normally regulated by the Nuclear Regulatory Council (NRC). These are normally enforced in the restricted areas where there are large amounts of ionization radiation emitted. Shielding a person using protective gear made of lead can also help to reduce the amount of exposure to radiation. The half layer for shielding can be defined by:

Figure 1: lab setup of the equipment
To calculate the layer thickness (H½ ) of different materials
Instruments and Materials
Geiger-Mueller counter Instrument
o One Tab of Cesium 137 (Cs) 137
o One Tab of Strontium 90 (Sr) 90
o Caliper
o Black crucible – unknown Radiation Material
o Aluminum square plate 2”x2” thickness- 1.60 mm (h)
o Wood 2”x10” board thickness – 6.00 mm (h
1) Place the radioactive material in a crucible.
2) Place the material to be tested between the material and the source of the radiation.
3) Place the crucible below the Geiger-Mueller counter and ensure that the counter is in counting mode.
4) Record the number of counts per unit time
5) Repeat the same process for the other material.
Table 1: Initial measurements
Geiger-Mueller counter
Without shielding (Ao)
Shielding with Aluminum (A1)
Shielding with wood
Unknown cup
0.2 x 10 = 2 Mr/hr
0.5 x 0.1= 0.05 Mr/hr
0.9 x 0.1= 0.09 Mr/hr
Cs 137
0.4 x 10= 4.0 Mr/hr
0.2 x 0.1= 0.02 Mr/hr
0.1 x 0.1= 0.01 Mr/hr
Sr 90
0.8 x 10 = 8 Mr/hr
0.4 x 1 = 0.4 Mr/hr
0.4 x 1 = 0.4 Mr/hr
Table 2: computed measurements
Geiger-Mueller counter
Wood (A)
Aluminium (A2)
Unknown cup
0.501 Mr/hr
Cs 137
1.002 Mr/hr
Sr 90
2.005 Mr/hr
h wood = 6.00 mm
h Aluminum = 1.60 mm
From the work carried out above, the main objective of the lab exercise was achieved as the half layer of the both wood and materials were computed. The half layer for aluminium with unknown cup was found to be 0.568 Mr/hr, using Cs137 it was found to be 1.137 Mr/hr and using Sr90, it was found to be 2.274 Mr/hr. For wood, it was found to be 0.023 Mh/hr for the unknown cup, using Cs137 it was found to be 0.00251Mr/hr and using Sr90, it was found to be 0.01002 Mr/hr.
Glenn F. Knoll: Radiation Detection and measurement, John Wiley & Sons, New York 1989 (2nd ed.), 1999 (3rd ed.)
William Leo: Techniques for Nuclear and Particle Physics Experiments: A How-To Approach; Springer Verlag, New York 1994 (2nd ed.)