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RADIATION PROTECTION TRAINING

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RADIATION PROTECTION TRAINING Charles F. Reindl, M.S., C.H.P. Certified Diagnostic Radiological Physicist Radiation Safety Officer Tulane University – PowerPoint PPT presentation

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Title: RADIATION PROTECTION TRAINING


1
RADIATION PROTECTIONTRAINING
  • Charles F. Reindl, M.S., C.H.P.
  • Certified Diagnostic Radiological Physicist
  • Radiation Safety Officer
  • Tulane University
  • Office of Environmental Health Safety

2
Table of Contents
  • Section 1
  • Radiological Fundamentals
  • Matter
  • Radioactive Decay Types of
  • Ionizing Radiation
  • Radiation Interactions
  • Radiation Exposure Units
  • External Exposure Measurement
  • Biological Effects of Radiation
  • Federal Limits for Occupational
  • Exposure to Ionizing Radiation
  • Section 2
  • Instrumentation Radiation/Contamination
  • Monitoring
  • Gas-Filled Detectors
  • Radiation Monitoring
  • Contamination Monitoring
  • Survey Frequency
  • Other Laboratory Rules
  • Section 3
  • Exposure Reduction
  • Inverse Square Law
  • Time
  • Shielding
  • Section 4
  • Radioactive Decay Specific Hazards
  • Decay Equation
  • Radioiodine
  • Tritium
  • Phosphorus-32
  • Section 5
  • Radioactive Materials Disposals
  • Decay to Background Levels
  • Sewer Disposal
  • Incineration
  • Transfer to a Licensed Disposal Firm

3
Radiological Fundamentals
Section 1
4
Section 1
  • Radiological Fundamentals
  • Matter
  • Radioactive Decay Types of Ionizing Radiation
  • Radiation Interactions
  • Radiation Exposure Units
  • External Exposure Measurement
  • Biological Effects of Radiation
  • Federal Limits for Occupational Exposure to
  • Ionizing Radiation

5
Section 1-A Matter
  • A. Matter
  • All matter is composed of atoms, and each atom is
    made up of three fundamental particles.
  • Symbol Name Mass Charge
  • p Proton 1 amu 1
  • e- Electron 0.0005 amu -1
  • n Neutron 1 amu 0

6
Section 1-A, continues Matter
  • An amu (Atomic Mass Unit) is approximately equal
    to the mass of a proton or neutron and
    numerically equal to 1.66 E-24 grams. The mass
    of an electron is negligible in comparison. Any
    atom can be symbolized by the following notation
  • AXZ where
  • X The chemical symbol of the element which is
    determined by the number of protons in its
    nucleus.
  • Z The Atomic Number, equal to the number of
    protons in its nucleus.
  • A The Mass Number, equal to the number of
    protons plus neutrons in its nucleus.

7
Section 1-A, continues Matter
  • There are three isotopes of the element hydrogen,
    symbolized "H.
  • The first isotope is H-1, the most common type of
    hydrogen with a natural abundance of 99.985.
  • The second isotope is H-2, heavy hydrogen, also
    called deuterium with a natural abundance of
    0.015.
  • The final isotope is H-3, radioactive hydrogen,
    also called tritium.
  • All three are isotopes of hydrogen and H-3, since
    it is radioactive, is also called a radioisotope
    or a radionuclide. In general, isotopes are
    atoms with the same number of protons (same Z),
    but different numbers of neutrons (different A).

8
Section 1-B Radioactive Decay
Types of Ionizing Radiation
  • B. Radioactive Decay and Types of Ionizing
    Radiation
  • Radioactive atoms become more stable by emitting
    one or more of the
  • following most common types of ionizing
    radiation
  • Alpha (a) A high speed helium nucleus (4He2)
    with no orbital electrons and a resulting 2
    charge overall.
  • Beta (ß) A high speed electron (e-) with a -1
    charge overall.
  • Gamma (?) An electromagnetic wave with no mass
    and no charge overall.

9
Section 1-C Radiation Interactions
  • C. Radiation Interactions
  • All ionizing radiations produce ion pairs as they
    travel through air, detection devices, shielding,
    or body tissue. These ion pairs are simply
    target atoms whose electrons have been stripped
    off by the ionizing radiation. If Y is any
    target atom
  • Y ionizing radiation -----gt Y e- where the
    two products are the ion pair. The formation of
    ion pairs may result in ionization of the air,
    ionization causing a pulse in a detector,
    heating of shielding, or biological damage
    depending on what the target atom is.
  • Particles with electric charge such as alphas and
    betas pull or push target electrons through
    charge-charge interactions (unlike charges
    attract while like charges repel) as they lose
    energy slowing down.
  • Ionizing electromagnetic waves such as gammas or
    X-rays (X-rays being simply low energy gammas)
    produce ion pairs by photointeractions producing
    recoil betas/electrons which go on to produce
    further ion pairs by charge-charge interactions.

10
Section 1-D Radiation Exposure Units
  • D. Radiation Exposure Units
  • Radiation exposure can be measured by use of the
    following units, listed in
  • order from oldest to most modern
  • Roentgen (R) - The amount of gamma or X-radiation
    producing one esu (electrostatic unit) of ion
    pairs in a cubic centimeter (cc) of dry air.
    This amounts to about two billion ion pairs in a
    cc of air.
  • This same amount of gamma or X-radiation produces
    approximately one.
  • Rad (Rad) - The amount of any type of radiation
    depositing 100 ergs of energy per gram of any
    material. This amounts to about two trillion ion
    pairs in a gram (g) of air, one gram of air being
    about a thousand cubic centimeters, and about the
    same number of ion pairs in a gram of body
    tissue.

11
Section 1-D, continues Radiation Exposure
Units
  1. Numerically, one Rad 100 ergs/g of absorbed
    radiation.
  2. One Roentgen of gamma or X-radiation produces
    about one Rad (100 ergs/g) of absorbed
    dose and also one.
  3. Rem (rem) - The amount of any type of radiation
    producing biological damage equivalent to that
    deposited by 100 ergs of gamma or X-radiation per
    gram of body tissue. In other words, a rem of
    any type of radiation will always produce the
    same amount of harm to living tissue as would a
    Rad of gamma or X-radiation. The damage produced
    by gamma or X-radiation becomes the standard by
    which all other types of radiation are measured.
  4. Numerically, one rem the dose equivalent to 100
    erg/g of or X-rays.

12
Section 1-D, continues Radiation Exposure
Units
  • Gammas and x-rays generally cause a spray of
    recoil electrons (betas) when they interact with
    cells through photointeractions. These recoil
    betas, because of their -1 charge and high speed,
    then produce relatively dispersed damage among
    many cells. Because (?/?-radiation produces
    recoil betas, ß/?/?-radiation produce the same
    number of Rads and rems.
  • The Roentgen, Rad, and rem are relatively large
    units relative to research laboratory work, so
    subunits in the milli (one thousandth) range are
    frequently employed.
  • Note that 1 R 1000 mR
  • 1 Rad 1000 mRad
  • 1 rem 1000 mrem

13
Section 1-E External Exposure
Measurement
  • E. External Exposure Measurement
  • Alphas will never penetrate the outer layer of
    dead skin if present in an external radiation
    field and are therefore never counted as external
    exposure. However, ingested or inhaled alpha
    sources will deliver their entire absorbed
    radiation dose.
  • Betas will penetrate as far as living skin if
    present in an external radiation field,
    contributing to external skin/shallow dose.
  • Gammas, having no charge to interfere with their
    progress, will penetrate living skin, internal
    organs, and possibly re-emerge from the far side
    of the body because of their great range. They
    are counted as part of the skin/shallow and whole
    body/deep dose because their recoil betas can be
    produced anywhere and impart biological damage at
    that location.
  • Note An "M" reading under deep/whole body or
    shallow/skin exposure reported on a Landauer
  • Radiation Dosimetry Report means "Less than the
    Minimum Detectable Exposure."

14
Section 1-F Biological Effects of
Radiation
  • F. Biological Effects of Radiation
  • Cell sensitivity to radiation is determined by
    two primary factors
  • Level of cell activity resulting in increased
    rates of chemical diffusion across the nuclear
    membrane.
  • Rate of cell division resulting in more time
    spent with the protective nuclear membrane
    dissolved.
  • Other factors apply but will be discussed later.

15
Section 1-F, ContinuesBiological Effects of
Radiation
  • These criteria can be used to list the body's
    cells and organs in approximate order from most
    to least radiosensitive
  • Fetal tissue
  • Reproductive cells (for long term genetic
    reasons).
  • Red and white blood forming cells primarily
    located in the bone marrow.
  • Lens of eye.
  • Most internal organs such as the lung and lower
    intestine.
  • Skin of the whole body, thyroid, nerve, etc.
  • Extremities such as hands and feet.
  • In order to put the rem into its proper
    biological perspective, it is useful to compare
    it to the effects of large acute exposures which
    are received in 24 hours or less.

16
Section 1-F, ContinuesBiological Effects of
Radiation
  • CAUTION The exact boundary of each exposure
    range depends on
  • individual health and the availability of
    medical treatment after exposure.
  • rem Immediate Effects
  • 0 - 25 None
  • 25 - 100 Small measurable changes in white blood
    cell count.
  • 100 - 200 Possible symptoms of radiation
    sickness
  • Blood changes including a white blood cell
    decrease
  • leading to decreased disease resistance, a red
    blood
  • cell decrease leading to fatigue, and a blood
    platelet decrease leading to a decreased
    ability of blood to clot over wounds.
    Intestinal wall damage leading to nausea,
    vomiting, and diarrhea.

17
Section 1-F, ContinuesBiological Effects of
Radiation
  • Note The severity of symptoms increases with
    increasing exposure until the following
    approximate exposures are reached
  • 500 Lethal Dose to 50 if those exposed within
    30 days (LD50/30) along with epilation (loss
    of hair) within two
  • weeks.
  • 1000 Additional symptoms include convulsions due
    to Central
  • Nervous System damage.
  • The American Cancer Society states that 25 of
    the 20 to 65 year old age group develops cancer
    from sources such as errors in gene duplication,
    smoking, air pollution, food, and natural
    background radiation. An increased exposure of 1
    rem would increase the risk of cancer from about
    25 to about 25.03.

18
Section 1-F, ContinuesBiological Effects of
Radiation
  1. This assumed linear relationship between
    radiation exposure and the risk of effects
    provides the rationale for Federal limits on
    radiation exposure to the whole body including
    bone marrow, genetic material, trunk and head.
  2. A "background" exposure rate exists naturally.
    In the U.S., the natural background radiation
    exposure rate is about 100 mrem/year from traces
    of naturally occurring Uranium and Thorium in
    soil and building materials, traces of naturally
    occurring K-40 and C-14 in foods, and cosmic
    radiation. Including an average number of
    medical and dental X-rays, the total U.S. average
    increases to about 200 mrem/year.

19
Section 1-GFederal Limits
for Occupational Exposure to Ionizing Radiation
  • G. Federal Limits for Occupational Exposure to
    Ionizing Radiation
  • The occupational limits set forth in Title 10,
    Code of Federal Regulations, Part 20 (10 CFR 20)
    and Louisiana State Regulations apply to those
    with a complete prior occupational radiation
    exposure history.
  • The limit for occupational exposure to ionizing
    radiation is 5,000 mrem/year.
  • The Federal limit for pregnant women is based on
    exposure to the fetus which is very
    radiosensitive.
  • The limit for radiation exposure to the fetus is
    500 mrem/term.

20
Instrumentation andRadiation/Contamination
Monitoring
Section 2
21
Section 2
  • Instrumentation and
  • Radiation/Contamination Monitoring
  • Gas-Filled Detectors
  • Radiation Monitoring
  • Contamination Monitoring
  • Survey Frequency
  • Other Laboratory Rules

22
Section 2-AGas-Filled
Detectors
  • A. Gas-Filled Detectors
  • Once again, radiation interactions produce ion
    pairs. Gas-filled detectors generally consist of
    an outer container along with an inner wire
    placed inside and along the long axis of the
    detector probe. Container (outer electrode) and
    wire (inner electrode) are electrically insulated
    while the outer container is generally given a
    negative charge and the inner wire a positive
    charge.
  • With voltage on the electrodes, an electric field
    is created which attracts the negatively charged
    electrons to the positive inner electrode and the
    positively charged ions to the negative outer
    electrode. A voltage drop or current increase is
    produced in the attached detector circuitry which
    is amplified and counted as a pulse.

23
Section 2-BRadiation
Monitoring
  • B. Radiation Monitoring
  • Radiation levels must be measured in order to
    determine the rate at
  • which dose is being received. This can only be
    done by using
  • radiation survey meters.
  • Before performing a radiation survey, the
    following preoperational
  • checks of the survey meter are recommended
  • Battery check the instrument by turning the range
    selection switch to the battery check position to
    see if the meter measures adequate voltage in the
    "Battery O.K." region.
  • Source check the instrument with a check source
    on contact with the meter probe. The meter
    should respond to radiation.

24
Section 2-CContamination
Monitoring
  • C. Contamination Monitoring
  • Activity (amount of radioactive material) can be
    measured in units or subunits of the Curie (Ci).
  • Note that 1 Ci 1,000 mCi 1,000,000 µCi
  • Example An incoming source vial contains 0.25
    mCi of P-32.
  • How many µCi is this?
  • 0.25 mCi X 1,000 µCi/mCi 250 µCi
  • Loose contamination can be picked up and spread
    to other areas. It is measured by taking a
    "wipe" such as a piece of filter paper, cloth, or
    a cotton-tipped swab and rubbing it over a
    specified area. Most frequently a 100 cm2 area
    which is about 4 inches by 4 inches is used as a
    standard. The smear is then beta or gamma
    counted. The loose activity is then calculated
    as in the following example

25
Section 2-C,
continuesContamination Monitoring
  • Example A cotton-tipped swab wiped over 100 cm2
    area of a fume hood surface produces 50,000
    counts per minute (cpm) above background on
    contact with a survey meter. The Conversion
    Factor on the calibration sticker of the meter
    reads "1 µCi 100,000 cpm". What is the loose
    surface contamination level in the fume hood?
  • 50,000 cpm X 1 µCi/100,000 cpm 0.5 µCi/100
    cm2
  • A laboratory sample counter can be used to
    measure lower levels of contamination more
    accurately, as long as a standard with a known
    number of µCi is used to determine the conversion
    factor from µCi to cpm. This is the same as
    determining the efficiency of the counter.

26

Section 2-DSurvey Frequency
  • D. Survey Frequency
  • Laboratories which use radioactive materials
    continuously must be surveyed weekly and the
    survey results recorded. Infrequent use
    laboratories must be surveyed at the completion
    of the procedure.
  • A record of these surveys, even if negative, must
    be kept on file for inspection by State or
    Federal regulators.

27

Section 2-EOther Laboratory Rules
  • E. Other Laboratory Rules
  • Decontamination of work areas must be performed
    when
  • contamination levels exceed twice background.
  • Refrigerator/freezers that are used to store
    radioactive materials must be labeled Caution,
    Radioactive Materials.
  • Incoming radioactive material packages labeled
    White I, Yellow II, or Yellow III must be wipe
    tested for radioactive contamination and the
    results recorded. This requirement is not
    applicable if the packages arrive at 333 South
    Liberty Street since the Radiation Safety Office
    checks these packages for contamination on a
    daily basis.
  • Radioactive materials must be secured when not in
    use by storing them in a locked container or
    locking the laboratory door when absent from the
    room.

28
Exposure Reduction
Section 3
29
Section 3
  • Exposure Reduction
  • Inverse Square Law
  • Time
  • Shielding

30

Section 3-AInverse Square Law
  • A. Inverse Square Law
  • The Inverse Square Law for gamma point sources
    is
  • D1 X r12 D2 X r22
  • Example The dose rate one foot away from a point
    source is 100 mrem/hr. What is the dose rate
    after stepping back to a distance of two feet?
  • D2 (100 mrem/hr) X (1 ft)2/(2 ft)2 25
    mrem/hr
  • As can be seen from the previous example,
    doubling distance from a point source of
    radiation decreases dose rate to one quarter of
    what it was. This is the basis of the Inverse
    Square Law and dose reduction by increasing
    distance.

31

Section 3-BTime
  • B. Time
  • The time equation, which is applied frequently in
    radiation protection work, is
  • Dose D x T where
  • D Dose rate
  • T Time of exposure
  • Example A researcher stands in an area where a
    survey meter reads 50 mrem/hr for a period of six
    hours. What is their total exposure as a result?
  • 50 mrem/hr X 6 hr 300 mrem

32

Section 3-CShielding
  • C. Shielding
  • The range of a beta is sufficient to penetrate
    living skin. Because of its -1 charge, a few
    millimeters of plastic can stop all betas.
  • Recall that gammas and X-rays are electromagnetic
    waves with no mass or charge and very
    penetrating. One Half Value Layer (HVL) is the
    thickness of shield material that will reduce
    exposure rate to one half of its initial amount.
    The thickness that reduces the incident flux to
    one half will, if doubled in thickness, reduce
    the original incident flux to one quarter of what
    it was.
  • In equation form D D0 (1/2)n and n x/HVL
    where
  • D0 Unshielded dose rate.
  • D Shielded dose rate.
  • n Number of Half Value Layers.
  • x Shield thickness.

33
Section 3-C,
continuesShielding
  • Example A source is producing a dose rate of
    100 mrem/hr at the side of a laboratory bench.
    Estimate the remaining dose rate from the source
    if two 1/2 inch lead shields are placed over the
    source. The HVL is 0.5 inch for the gamma energy
    involved.
  • The total thickness of lead shielding is 1.0
    inch and
  • n 1.0 in/0.5 in 2
  • D (100 mrem/hr) X (1/2)2 25 mrem/hr

34
Radioactive Decay and Specific Hazards
Section 4
35
Section 4
  • Radioactive Decay Specific Hazards
  • Decay Equation
  • Radioiodine
  • Tritium
  • Phosphorus-32

36

Section 4-ADecay Equation
  • A. Decay Equation
  • The following is the decay equation
  • A A0(1/2)n where
  • A0 Activity initial.
  • A Activity final.
  • n t/t1/2 Number of half-lives that have
    elapsed.
  • t Time that has elapsed.
  • Example A radioactive sample has a half-life of
    30 minutes. If the sample initially contained 1
    mCi, how much remains after 60 minutes?
  • n 60 min/30 min 2 elapsed half lives
  • A 1 mCi X (1/2)2 0.25 mCi
  • The example is simple but illustrates the point
    that one half-life of time will decrease a given
    amount of radioactivity to one-half of what it
    was.

37

Section 4-BRadioiodine
  • B. Radioiodine
  • Radioiodine is most commonly I-125 with a 60 day
    half-life. It produces a relatively low energy
    35 keV gamma/x-ray in only 7 of the decays.
    When purchased as sodium iodide (NaI) in base
    (NaOH) the radioiodine is relatively stable and
    water soluble. Under acidic conditions, sodium
    iodide chemically partitions to form volatile
    elemented iodine (I2) which can be inhaled. Due
    to its rapid biological accumulation in the
    thyroid, thyroid monitoring is necessary.
    Radioiodine is primarily an airborne thyroid
    hazard.

38

Section 4-CTritium
  • C. Tritium
  • Tritium, H-3, has a 12.3 year half-life.
  • It produces a 19 keV beta and no gamma.
  • Tritium is an internal exposure hazard.
  • Rubber gloves must always be used when handling
    radionuclides.
  • Including tritium since it can be absorbed
    through bare skin.
  • Urinary monitoring, which is done by collecting a
    milliliter of urine to be mixed with
    scintillation medium and counted, must be
    performed when using large amounts of tritium.

39

Section 4-DPhosphorus-32
  • D. Phosphorus-32
  • Phosphorus-32 (P-32) has a 14.3 day half-life and
    emits a 1,710 keV beta with no gamma.
  • P-32 is an external skin/shallow exposure hazard,
    while not a whole body/deep dose hazard.
  • It can also deliver a large dose to the hand when
    handled in mCi amounts.

40
Radioactive Materials Disposal
Section 5
41
Section 5
  • Radioactive Materials Disposal
  • Decay to Background Levels
  • Sewer Disposal
  • Incineration
  • Transfer to a Licensed Disposal Firm

42

Section 5-ADecay to Background Levels
  • A. Decay to Background Levels
  • Radioactive waste may be discarded in the normal
    waste stream if the following conditions are met
  • The material has decayed 10 half-lives.
  • The waste produces no count rate above background
    on contact with a radiation survey meter.
  • All "Radioactive" labels have been
    removed/defaced.
  • Notation is made on the "Radionuclide Receipt
    Use Record" that the waste has been defaced
    discarded, bkg, and date.
  • Note Accurate Radionuclide Receipt and Use
    Records prove to Federal and State auditors that
    radioactive material has been used and disposed
    of in a safe and legal manner.
  • After decay, the waste may still be hazardous or
    infectious and have to be disposed of in one of
    these specialized waste streams.

43

Section 5-BSewer Disposal
  • B. Sewer Disposal
  • Aqueous liquid radioactive waste may be disposed
    of in the laboratory "hot sink" along with
    copious amounts of water as long as the date,
    radioisotope, and activity disposed of is
    recorded.
  • Its very important to note that this method may
    only be used if the sewer is connected to a
    municipal sewer system.
  • A "Semi-Annual Radionuclide Inventory/Sewer
    Disposal" report is requested of each licensee
    every six months. These are used by the
    Radiation Safety Office to ensure that the
    activity concentrations leaving each building are
    below drinking water concentration limits and
    that the total activity discharged is less than 1
    Ci per year.

44

Section 5-CIncineration
  • C. Incineration
  • Contaminated laboratory trash and biodegradable
    liquid scintillation vials can be taken to the
    Medical School waste room, tagged with the
    radioisotope, activity amount in µCi, date, and
    licensee name for eventual incineration.
  • The Waste Room is located in room 1105 of the
    Medical School and is open Tuesdays from 830 to
    1030 a.m.
  • The Radiation Safety Office ensures that the
    amount of radioactivity incinerated per hour does
    not cause effluent air concentrations to exceed
    the limit for unrestricted air and that the
    resulting incinerator ash does not exceed
    drinking water concentration limits.

45

Section 5-DTransfer to a Licensed Disposal
Firm
  • D. Transfer to a Licensed Disposal Firm
  • Organic liquid scintillation cocktail such as
    toluene containing radioisotopes with long
    half-lives must be transferred to a licensed
    radioactive/chemical waste disposal company.
  • The Radiation Safety Office will arrange these
    shipments, but must bill the licensee generating
    the waste because of the high price of such
    disposal.

46
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