RADIATIONS, IONIZING RADIATION, X-RAYS, Y-RAYS, ALPHA RAYS, BETA RAYS, GAMMA RAYS, PROTECTION FROM IONIZING
Gamma rays, Alpha rays
RADIATIONS, IONIZING
RADIATION, X-RAYS, Y-RAYS, ALPHA RAYS, BETA RAYS, GAMMA RAYS, PROTECTION FROM
IONIZING.
Ionizing radiation activities are regulated by the responsibility
of the company and Contractors to comply with its applicable regulations.
However, the following shall provide a framework for
Ionizing Radiation Management.
Ionizing radiation occurs either as electromagnetic rays
(e.g. X-rays and gamma γ-rays) or as particles, but it also occurs naturally
from the radioactive decay of natural substances such as radon gas.
Industrial
Radiography
Industrial radiography is a method of inspecting materials
for seeing hidden flaws by using the ability of
X-rays, gamma rays, and neutrons penetrate various
materials. It is a major element of non-destructive testing.
Industrial radiography for non-destructive testing is used
to inspect, among others, concrete and a wide variety of welds, such as those
in gas and water pipelines, storage tanks, and structural elements. It can
identify cracks or flaws that may not be otherwise visible. These
characteristics have made nondestructive testing a key tool for quality
control, safety, and reliability. Industrial radiography uses two types of
radiation; namely x-rays and gamma (γ) rays.
X-Rays and γ-Rays
X-rays used in Non-Destructive Inspections are produced by a
large generator that is used in a fixed location and similar to medical x-ray
machines, radiation is present only when these machines are turned on. Portable
industrial radiography units are smaller in size as compared to X-ray machines
and use a negligible amount of radioactive gamma-emitting material in a sealed
source, which is typically less than 1 cm in diameter and a few centimeters
long. Portable industrial radiography units are heavy due to the shielding
which is added to protect operators from ionizing radiation.
X-ray machines are also used for medical imaging during
examination for orthopedic damage, lung disease, tumors, or foreign objects in
the human body, or for assessing tooth decay or damage
Alpha rays
Particles are helium nuclei that are heavy and positively
charged. This causes them to lose their energy very quickly in the matter and
thus can be easily stopped from further travel. They can be stopped by a sheet
of paper or the surface layer of the human skin. α particles are hazardous to
health only if inhaled or ingested.
Beta rays
Particles are much smaller compared to α particles and only
have one negative charge which causes them to interact more slowly with the material.
They are effectively stopped by thin layers of metal or plastic
some beta particles are capable of penetrating the skin and causing damage such
as skin burns. However, as with alpha emitters, beta-emitters are most
hazardous when they are inhaled or swallowed.
Gamma Rays
Emitters are associated with α and decay and are a form of
high-energy electromagnetic radiation that interacts lightly with the matter.
Gamma rays are best shielded by thick layers of lead or other dense materials and
are considered an external hazard to living tissues i.e. the human body.
Health Effects of
Ionizing Radiation
There are two routes for human exposure to ionizing
radiation, these are either (a) irradiation from an external source that
remains outside the body (e.g. X-ray machines, or during handling and working
with radioactive sources, and (b) contamination, where the radioactive material
enters the body by inhalation, ingestion or absorption.
Worker's Protection
from External Radiation
External radiation exposure involves an external source with
gamma radiation of which controls are straightforward as follows:
Minimize the time spent close to a NORM installation
(vessels, pipes, valves, pumps), or the exposure time when the workers are
handling NORM wastes during desludging.
The total dose a person will receive while near a NORM
installation or waste is directly proportional to the length of time for which the
worker is exposed. Therefore, unclassified workers managing NORM wastes must
limit the exposure time at which the effective dose rate is below the annual
dose rate of 1 mSv/year.
Worker's Protection from Internal Radiation
Internal radiation exposure involves an internal source with
Alpha and Beta particles, which enters the body by inhalation, ingestion, and
surface cuts. Internal radiation requires more stringent precautions than when
working only with gamma radiation as follows:
Employees and contractors shall be advised of the presence
and potential risks of NORM and of the procedures to minimize exposure.
Personnel radiation exposures at NORM-impacted sites shall
be assessed and the working area to be classified as described.
1.
Appropriate PPE shall be worn which may include
but is not restricted to the following:
2.
Disposable one-piece waterproof splash-proof coveralls.
3.
Impervious gloves Neoprene, PVC or NBR
4.
Rubber or PVC boots
5.
Eye protection with safety glasses with side
shields
6.
Safety hardhat
7.
Minimum required Respiratory Protective
Equipment whose wearer underwent a respirator fit test.
8.
Follow Personal Hygiene procedures to prevent
personal contamination.
9.
Follow Good Housekeeping procedures to control
the spread of contamination or contaminated equipment and waste.
10.
Keep NORM-contaminated equipment and waste e.g.
scale sludge wet all the time to minimize dust airborne generation during
handling.
11.
Any opening of NORM-contaminated equipment shall
be capped, sealed, or wrapped in a plastic sheet to minimize the spreading of
any dust.
12.
Eating, drinking, and chewing or applying
cosmetics e.g. sunscreen, lipstick) shall not be allowed in the immediate work
area where equipment soil containing NORM is being handled.
13.
Only designated personnel shall be allowed in
the work areas with potential
14.
NORM contamination.
CONTROL OF RISK
Once radiation risks have been identified and assessed,
resources shall be directed to establishing and implementing radiation control
strategies. At a minimum, site-specific Radiation Control Plans shall be established
based on requirements and prioritized based upon the class of risk i.e. High,
Highmedium, Medium, or Low in combination with the number of persons exposed
and the frequency and magnitude of the exposure. The site-specific Radiation
Control Plans shall aim to control exposures to radiation using one or a
combination of the following:
·
Reducing radiation exposure time
·
Increasing distance between works and radiation
sources
·
Intercepting radiation pathways.
Time
There is a direct relationship between radiation dose and
time of exposure. Therefore, Radiation
Control Plans shall include documented actions aimed to
reduce an individual’s radiation dose by controlling the amount of time exposed
to radioactive sources and substances.
When exposed to high-risk radiation levels, an individual’s
dose levels shall be routinely monitored during work using personal dosimeter
alarms.
Distance
Increasing the distance between a radiation source and a
person will reduce the person’s exposure to radiation.
Occupational environment monitoring results shall be
utilized to establish and demarcate site-specific Controlled Areas and
Supervised Areas.
Physical barriers and warning signs shall be erected to
indicate where Controlled Areas and Supervised Areas exist and shall allow an
appropriate minimum separation distance between work areas and Unclassified Workers.
Shielding
Radioactive sources shall be effectively shielded to ensure
the maximum effective dose rate on the surface of the container does not exceed
2 mSv/hr.
At a minimum, the selection of radiation shielding shall
consider the following:
1.
The type of radiation requiring shielding
2.
The desired effect of the shielding
3.
The availability of required shielding materials
4.
The maintenance and inspection requirements for
the shielding
5.
The frequency and extent of use.
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