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Radiation Safety Training Dose limits and Dosimetry Washington State University Radiation Safety Office

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Units Used in Radiation Safety erg Roentgen Rad Rem Curie Sievert Becquerel Gray joule Units Definitions Really it s not that hard. Energy ft lb, erg, joule ... – PowerPoint PPT presentation

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Title: Radiation Safety Training Dose limits and Dosimetry Washington State University Radiation Safety Office


1
Radiation Safety TrainingDose limits and
DosimetryWashington State UniversityRadiation
Safety Office
2
Units Used in Radiation Safety
  • erg

Rad
Sievert
Roentgen
joule
Curie
Rem
Gray
Becquerel
3
Units Definitions Really its not that hard.
  • Energy
  • ft?lb, erg, joule,
  • electron-volt (1 eV 1.6 x 10-19 joules)
  • Others meV, keV, MeV, GeV, TeV
  • 1 erg 10-7 joule

James Prescott Joule
One foot-pound is the amount of energy expended
when one pound-force acts through a distance of
one foot along the direction of the force. An
electron volt (symbol eV) is equal to the amount
of kinetic energy gained by a single unbound
electron when it accelerates through an
electrostatic potential difference of one volt.
4
Units cont. The Roentgen
  • Roentgen (symbol R) (coulomb/kg)
  • 1 R 2.58 x 10-4 C./kg
  • (1 esu charge in 1.293 mg of air)
  • 87.6 ergs/gm for air

Exposure
Wilhelm Conrad Röntgen
The röntgen or roentgen (symbol R) is a unit of
measurement for ionizing radiation, and is named
after the German physicist Wilhelm Röntgen.
Adopted in 1928, 1 R is the amount of radiation
required to liberate positive and negative
charges of one electrostatic unit of charge (esu)
in 1 cm³ of dry air at standard temperature and
pressure (STP). This corresponds to the
generation of approximately 2.08109 ion pairs.
5
Units cont.The Rad
  • Absorbed Dose
  • Rad (or Gray in SI units)
  • 1 R ? 95 ergs/gm for tissue
  • 1 rad 100 ergs/gm
  • 1 gray (Gy) 0.01 J/kg 100 rad

Louis Gray
The rad (radiation absorbed dose) is a unit of
absorbed radiation dose, with symbol rad. It was
defined in CGS units in 1953 as the dose causing
100 ergs of energy to be absorbed by one gram of
matter. It was restated in SI units (Gray) in
1970 as the dose causing 0.01 joule of energy to
be absorbed per kilogram of matter. To gauge
biological effects the dose in rads is multiplied
by a 'quality factor' which is dependent on the
type of ionizing radiation. This modified dose is
now measured in rems (roentgen equivalent mammal,
or man)
6
Units cont.The REM
  • Dose Equivalent
  • Rem (or Sievert in SI units)
  • H QD (H in rem if D in rad)
  • Q is quality factor (Effects of Type of
    Radiation)
  • 1 for e?, x, ?
  • 2-10 for neutrons (E - dependent)
  • 10 for protons
  • 20 for alpha
  • 1 sievert (Sv) 100 rem
  •  

Rolf Sievert
A Rem is a unit of measurement also known as
dose equivalent which numerically describes the
relative amount of biological damage which occurs
from doses of ionizing radiation. The rem is
derived by the product of the dose received in
rads and a quality factor which is unique to each
type of radiation. This equates the effectiveness
of each type of radiation to cause biological
damage. The rem is used to report doses to
persons or organs.
7
How much is a millirem (mrem)?
  • The annual background radiation exposure for a
    typical American is 620 mrems.
  • The average dose from watching color TV is 2 mrem
    each year.
  • The granite from Grand Central Station exposes
    its employees to 120 mrem of radiation each year
  • People in Denver receive 50 mrem more each year
    than those in LA because of the altitude.
  • The nuclear industry contributes to less than 1
    mrem/year to an individuals background
    radiation.
  • A millimrem is a small unit of measure.

8
A millirem measures the amount of radiation
energy absorbed into the tissue.
  • 1000 millirems 1 rem 0.01 Gy

1 Gy1 Joule /kg times a quality factor to adjust
for the type of radiation (alpha, beta, or
gamma)
But how much energy is that?
Therefore 4.16 Gy would produce the same amount
of energy it would take to heat up 1 milliliter
of water 1 degree C.
9
Units Cont. The Curie
  • Activity
  • Curie (or Becquerel in SI units)
  • 1 Becquerel (Bq) 1 dis./sec
  • 1 curie (Ci) 3.7 x 1010 dis./sec
  • 1 curie (Ci) 2.22 x 1012 dis./min
  • 1 mCi 37 MBq

A Curie is a unit of measurement which
quantifies the amount of radioactivity present as
a disintegration rate. One Curie (Ci) is
referenced as the amount of radioactivity present
in 1 gram of radium and is equivalent to 3.7 x
1010 disintegrations per second (DPS).
Henri Becquerel
Marie Curie
10
DOSE LIMITS
  • How much dose am I allowed to get?
  • Dose is usually reported in rems or millirems
    (mrem).

11
MAXIMUM PERMISSIBLE DOSE FOR OCCUPATIONAL
WORKERSAnnual Limits (rems)
  • An annual limit, the more limiting of
  • (1) Total effective dose equivalent,
    or----------------5 rem (0.05 Sv)
  • (2) Sum of deep dose equivalent and committed
    dose equivalent to any organ or tissue (not lens
    of eye)50 rem (0.5 Sv)
  • ANDAnnual limits to lens or eye, to skin, and to
    extremities of
  • (1) Eye dose equivalent of -----------------------
    ------15 rem (0.15 Sv)
  • (2) Shallow dose equivalent to skin or
    extremity50 rem (0.5 Sv)

12
MAXIMUM PERMISSIBLE DOSE SPECIAL CASES
  • FERTILE WOMEN
  • 0.5 rem (5 mSv) for 36 weeks (the period of
    gestation, the fetus is also monitored.)
  • If a woman decides to declare herself pregnant,
    she must do so in writing to her supervisor (the
    authorized user) and to the radiation safety
    office. A fetal monitoring badge will be issued.

13
MAXIMUM PERMISSIBLE DOSE SPECIAL CASES (cont.)
  • ALL WOMEN
  • Immediate supervisors are responsible for
    ensuring that any woman who works with ionizing
    radiation reads S90.75.2 in the WSU Safety
    Policies and Procedures Manual. "Possible Health
    Risks to Children of Women Who Are Exposed to
    Radiation During Pregnancy.Women employees must
    sign the Prenatal Radiation Exposure Statement
    form after reading S90.75.2
  • Print the Prenatal Radiation Exposure Statement
    form on page S90.75.16.Return the original
    signed form to the Radiation Safety Office.
    Retain a copy for departmental files.

14
MAXIMUM PERMISSIBLE DOSE SPECIAL CASES (cont.)
  • MINORS - Persons Under 18 years old.
  • MEMBERS OF THE PUBLIC
  • 0.5 rem for 52 weeks
  • 100 mrem (1 mSv) for 52 weeks from controlled
    sources of ionizing radiation.

15
RADIATION SAFETY OFFICEDosimetry Program
  • The Radiation Safety Office issues
    Personnel Dosimetry
  • About 850 Persons are badged at WSU.

16
Dosimetry Program
  • Two Types External dosimetry
  • Internal dosimetry.
  • Dosimeter A device used to estimate the amount
    of external radiation dose to the body.
  • External Dosimetry
  • Whole body badge Monitors whole body exposure
    to b, g, X-ray
  • and neutrons.
  • Extremity badge Monitors exposure to hands or
    feet.
  • Pocket dosimeter Direct reading instrument that
    monitors real time whole body
    exposure.

17
Dosimetry Program
  • TLD Ring
  • Thermoluninescence dosimeter
  • Worn on index finger of dominant hand, with
    the white face turned towards the radiation
    source.
  • OSL Body Badge
  • optically stimulated
  • luminescence
  • Worn on torso, below chin
  • and above waist

External dosimetry
18
Dosimetry Program (CONTINUED)
Internal Dosimetry
  • Internal Dosimetry - A technique used to monitor
    the dose from radioactive materials
    taken into the body.
  • Urinalysis Analyzing urine samples to
    determine the amount of radionuclide
    excreted by the human body.
  • Thyroid monitoring To determine the amount of
    radioactive iodine (125I and 131I) in the
    thyroid.
  • Whole body counting This procedure would be
    performed elsewhere, if necessary.

19
Occupational Exposure record.
If you are required to wear a badge (dosimetry).
Once a year you will receive an exposure report.
This report tells you what your radiation
exposure was for the previous year. This person
received 16 mrem (0.016 rem). Far below the 5 rem
limit. ALARA As Low As Reasonably Achievable.
20
Dosimetry Dos and Donts
  • Always wear your dosimetry, both body and ring,
    badges if required! Required by WAC 246-235-130
  • Never allow anyone else to use your dosimetry.
  • Most dosimetry is changed out quarterly, every
    three months. Return your previous dosimetry to
    the Radiation Safety Office prior to the 10th of
    the change out month.
  • Do not use radioactive materials or radiation
    machines without your dosimetry, if required.

21
Test Time!
  • Follow this link to the test. https//myresearch.w
    su.edu
  • Use your WSU user name and password to sign in.
  • Click on the training tab.
  • Then click on the available training tab
  • Find the radiation safety training dose limits
    course, in the OR section, click on it and
    take the test.
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