RADIATION SAFETY IN INDUSTRY INVOLVING NORM/ TENORM

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RADIATION SAFETY IN INDUSTRY INVOLVING NORM/
TENORM
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Contents

• Introduction
• Sources of Radiation
• Naturally Occurring Radioactive Materials (NORM)
• Non-series Radionuclide Contribution to
  Background Radiation
• Technologically Enhanced Radioactive Materials
  (TENORM)
• Radionuclide in Oil and Gas Scales
• Radionuclide in Coal and Coal Ash
• Uranium-Thorium Decay Series
• Radiation Risk Control
• Classification of Working Area
• Radiation Control
• Radiation Monitoring
• Handling and Storage of NORM/TENORM

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Introduction

• Man is continuously exposed to ionizing radiation
  which originates from naturally occurring
  radiation.
• Radioactive materials and man-made radiation
  sources are always present in his environment.
• In some places background radiation contributes
  significantly to human annual radiation dose
  exposures.
• Sometimes Naturally Occurring Radioactive
  Materials (norm) are technologically enhanced
  following extraction of other valuable minerals
  yielding TENORM or Technologically Enhanced
  Radioactive Materials (e.g. oil and gas industry
  and tin mining).

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Sources of Radiation

• NORM are scattered in low concentration or
  abundance in various samples such as soil,
  sediment, air, water and living organisms.
• Natural radiation originates from 3 types of
  sources
• Cosmic rays
• Cosmogenic radionuclides
• Primodial radionuclides

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Sources of Radiation

• Cosmic radiation
• Originate from the stars of outer space.
• Consist of proton ( 85 ), alpha particle ( 14
  ) and heavy nucleus ( 1 ).
• Primary cosmic rays interact with the upper
  atmosphere and produce secondary cosmic rays
  consisting of muon (70) and electron (30).
• Cosmic rays contribute around 300 ?Sv of total
  natural radiation exposure.

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Sources of Radiation

• Cosmogenic radionuclides
• Are radionuclides produced following
  interactions of cosmic rays with particles in the
  atmosphere.
• Examples of cosmogenic radionuclides
  are C-14, H-3, N-15.

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Sources of Radiation

• Primordial radionuclides
• Radionuclide that coexisted during the creation
  of earth.
• Radionuclide have very long half life, i.e.
  t1/2 gt108 years e.g. U-235, U-238, Th-232, K-40
  and Rb- 87.

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Annual per Capita Dose
Sources of Radiation
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Naturally Occurring Radioactive Materials (NORM)

• Examples of NORMS are
• Natural uranium consisting of U-238 (99.28),
  U-235 (0.715) and U-234 (0.005) Natural uranium
  consisting of U-238 (99.28), U-235 (0.715) and
  U-234 (0.005).
• U-238 decay series consists of 14 radionuclide.
• At secular equilibrium, total U-235 activity is
  11 times higher than any of its progenies.
• This series consists of 7 alpha emitters and 4
  beta emitters and finish with a stable Pb-207
  nuclide.  

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Naturally Occurring Radioactive Materials (NORM)

• Radon (Ra-222) is a gaseous decay product of
  Ra-226 (from U-238 series).
• Thoron (Rn-220) is a gaseous decay product of
  Ra-224 (from Th-232 series).
• Actinium series does not play a significant role
  in industrial TENORM due to its very low presence
  (1/6 of U-238) in the natural environment.
• If not subjected to chemical or physical
  separation, each of these series attains a state
  of secular radioactive equilibrium.
• Technological enhancement of NORM as well as
  natural physical and chemical reactions often
  interferes with this balance.

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Radionuclides in Uranium Mining
Naturally Occurring Radioactive Materials (NORM)
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Radionuclides Half-Lives
Naturally Occurring Radioactive Materials (NORM)
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Radionuclides Half-Lives
Naturally Occurring Radioactive Materials (NORM)
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Non-Series Radionuclides Contribution to
Background Radiation

• Two primary non-series radionuclides that
  contribute to background dose are K-40 and Rb-87.
• Potassium-40
• K-40 is a beta (87.3) and gamma (10.67) emitter
  and contributes to both internal and external
  doses.
• K-40 exists as a constant fraction of stable
  potassium (0.0117).
• Its contribution to external dose varies
  depending on its concentration in rocks and soil.
• Average concentration K-40 is about 0.6 Bq/g (17
  pCi/g) in crustal rock.

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Non-Series Radionuclides Contribution to
Background Radiation

• Rubidium-87
• Ru-87 is a pure beta emitter and is found in
  crustal rock in concentrations of about 0.07 Bq/g
  (2 pCi/g).
• It is not an external hazard and is rarely
  considered in dose calculations.
• The remainder of the non-series radionuclides has
  combinations of half-lives, isotopic abundances,
  and elemental abundances such that they have
  negligibly small specific activities and are not
  significant in background dose calculations.

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Technologically Enhanced Radioactive Materials
(TENORM)

• Significant amounts are TENORM derived from tin
  mining, tin slag and amang processing activities.
• TENORM is also found in waste of petroleum
  sludge, oil scale, material or contaminated
  apparatus or facilities.
• Estimates suggest that up to 30 of domestic oil
  and gas wells may produce some elevated TENORM
  contamination.
• Uranium and thorium compounds are mostly
  insoluble in oil and gas and will remain in the
  underground reservoirs.
• Radium and radium daughter are soluble in
  formation water and extracted with oil and gas.

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Technologically Enhanced Radioactive Materials
(TENORM)

• Radionuclides of TENORM/NORM
• TENORM can be emitters of low and high LET
  radiation.
• Hazards associated with different LET radiation
  may be divided based on the modes of exposures,
  i.e. external and internal
• External exposure
• Hazards from gamma emitter radionuclide.
• Actual exposure dose depends on the volume of
  source, the distance between the worker and the
  source, the working hours and the shielding used.
• Internal exposure
• Exposure to radon (Rn-222) and thoron (Rn-220).
• Rn-220 and Rn-222 are radioactive gases and pose
  internal hazards if inhale.    

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Technologically Enhanced Radioactive Materials
(TENORM)

• Radionuclides of TENORM/NORM
• These alpha emitters will be trapped in the
  inhalation system especially in the bifurcations
  in the lungs producing radiation hot spots.
• Thoron
• A daughter of Th-232 decay series, with t1/2 of
  55 sec.
• Upon decay, it too produces alpha emitters that
  pose internal radiation hazard.
• Radon
• A daughter from the U-238 decay series, and with
  a half life of 3.8 days.
• Hazardous if inhale into the body because it will
  decay and produce more hazardous alpha emitter
  progenies e.g. Po-218, Pb-214, Bi-204 and Po-214.

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Technologically Enhanced Radioactive Materials
(TENORM)

• Radionuclides of TENORM/NORM
• Internal hazards may also be a consequence of
  ingestion of NORM or entry of NORM through other
  means such as cuts and open wounds
• Surface contamination
• NORM found in coal ash, tin slag, amang mineral
  or petroleum production processes may cause
  surface contamination of the apparatus/facilities
  and working area.
• Such contamination may cause internal and/or
  external radiation exposure.

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Radionuclide in Oil and Gas Scales

• Radium-226 is generally present in scales, and in
  higher concentrations than Ra-228.
• Typically, Ra-226 in scales is in equilibrium
  with its progeny, but Ra-228 is not.
• The nominal activity appears to be about three
  times greater for Ra-226 than for Ra-228.
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Radionuclides Concentration, Bq/g (pCi/g)
Ra-226 13.3 (360)
Pb-210 13.3 (360)
Po-210 13.3 (360)
Ra-228 4.44 (120)
Th-228 4.44 (120)
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Radionuclide in Coal and Coal Ash

• Coal ash contains TENORM that requires proper
  management and disposal.
• Coal contains naturally occurring uranium and
  thorium, coal ash may present a potential
  radiological risk to exposed individuals.
• The degree of risk will depend on the physical
  and radiological properties of the ash.
• The radioactivity of coal may vary over two
  orders of magnitude depending on the type of coal
  and the region from which it was mined.
• The concentrations of U-238 and Th-232 in coal
  average about 0.022 and 0.018 Bq/g (0.6 and 0.5
  pCi/g), respectively.

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Radionuclide in Coal and Coal Ash
Radionuclides Concentration, Bq/g (pCi/g)
U-238 0.12 (3.3)
U-234 0.12 (3.3)
Th-230 0.085 (2.3)
Ra-226 0.14 (3.7)
Pb-210 0.25 (6.8)
Po-210 0.26 (7.0)
U-235 0.0037 (0.1)
Pa-231 0.0059 (0.16)
Ac-227 0.0059 (0.16)
Th-232 0.077 (2.1)
Ra-228 0.066 (1.8)
Th-228 0.19 (3.2)
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Uranium-Thorium Decay Series
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Radiation Risk Control

• The best method of managing radiation hazard and
  risk in industries involved with NORM is through
  engineering control.
• Serious attempt must be made to reduce suspension
  of dust containing TENORM in the air, and the
  discharge into the effluent.
• The hierarchy of radiological hazard control is
  engineering design followed by management control
  and Personal Protection Equipment (PPE) should
  be considered last.

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Classification of Working Area

• One method of controlling TENORM hazards and
  risks is by classifying the working areas.
• Classification of working areas involves
  engineering as well as administrative controls.
• Engineering control refers to the design of such
  working areas to meet the classification
  requirements.
• Administrative control refers to procedures and
  instructions.

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Classification of Working Area

• Working areas should be classified as clean,
  supervise or control areas.
• Working area is classified as control area when
• External Dose rate is gt 7.5 µSv/hr
• Surface contamination gt 7 Bq/cm2
• Contamination of Suspended particles is gt 1 x
  10-2 Bq/m3
• Working area is classified as supervise area
  when
• External Dose rate is between 2.5 - 7.5 µSv/hr
• Surface contamination 2 - 7 Bq/cm2
• Contamination of Suspended particles is between 3
  x 10-3 - 1 x 10-1 Bq/m3

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Radiation Control

• Next best method of controlling radiation risk
  after elimination, is engineering control.
• Safe work procedure is one method of
  administrative control.
• A practical and appropriate safe working
  procedure is necessary to avoid or reduce the
  effects of external and internal radiation
  exposures from NORM/TENORM.

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Radiation Control

• The basic principle of external radiation
  protection (i.e. time, distance, and shielding)
  should be considered in all safe working
  procedures.
• All safe working procedures must be clear,
  concise and easy to follow by the users.
• Training on the use of procedures must be given.
• Safe working procedures must be reviewed
  periodically to ensure its intended effectiveness
  and efficiencies.

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Radiation Control

• Personal Protective Equipment (PPE) is last
  choice in radiation protection methods.
• PPE is used to reduce radiological risk, i.e. the
  probability of exposure and/or the impact of any
  accidental radiation exposure.
• PPE must be used in conjunction with other
  hazards and risks controls.
• Examples of PPE that should be considered when
  working with NORM/TENORM include
• Respirators to reduce the inhalation of dust
  containing radionuclide.
• Gloves and apron to reduce contamination of the
  body.
• Goggles to reduce contamination of the eyes.

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Radiation Monitoring

• Areas and personal dose exposure monitoring shall
  be conducted as prescribed according to the
  classification of the working areas.
• Records of area and personal dose monitoring
  should be kept and maintained as required by the
  relevant authorities.

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Handling and Storage of NORM/TENORM

• Activities related to NORM/TENORM usually involve
  large quantities but low activity concentrations
  of radionuclides.
• Amang processing produces large quantity of
  valuable minerals containing TENORM that are
  usually stored in open spaces and exposed to the
  elements (rain and wind).
• Storage areas with radiation level exceeding the
  permissible limit should be isolated and
  classified as restricted or prohibited area.

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Handling and Storage of NORM/TENORM

• Guidelines for amang storage areas
• The storage area should be far enough from the
  office, workers quarters or residential area
• If a close store room is used, it should be
  equipped with good ventilation system
• The storage area must be fenced and locked
• The storage area must be clearly labeled with
  radiation warning signs.
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• General transportation procedure within and
  outside premise
• Follow instructions related to LSA-1 category.

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Handling and Storage of NORM/TENORM

• Environmental surveillance/monitoring program
• Radiological Impact Assessment (RIA) is required
  and must be carried out at all stages of
  operations
• Before Operation to assess potential
  radiological risk to workers and the environment
  before operation begins.
• During Operation to assess new radiological risk
  not considered during the planning stage or that
  may arise as a consequence of changes made during
  operation.
• After or Shut Down Operation to asses
  radiological risk during shut down and return to
  normalcy operations.
• RIA for area and personal monitoring should be
  part of the organization Radiation Safety
  Management System (RSMS).

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Summary
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