Transcript Radiation Safety Training Dose limits and Dosimetry

Radiation Safety Training
Dose limits and Dosimetry
Washington State University
Radiation Safety Office
Units Used in Radiation Safety
erg
Sievert
Rad
Roentgen
joule
Curie
Rem
Gray
Becquerel
Units Definitions
Really it’s 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.
Units cont.
The Roentgen
Exposure:
Wilhelm Conrad Röntgen
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
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 2.08×109 ion pairs.
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)
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.
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
individual’s background radiation.
•A millimrem is a small unit of measure.
A millirem measures the amount of radiation
energy absorbed into the tissue.
1000 millirems =1 rem =0.01 Gy
1 Gy=1 Joule /kg times a quality factor to adjust for the type of
radiation (alpha, beta, or gamma)
But1 Joule
how
much energy is that?
= 0.24 calorie
1 calorie=amount of energy to heat up 1 milliliter of water 1
degree C.
Therefore 4.16 Gy would produce the same amount of energy it
would take to heat up 1 milliliter of water 1 degree C.
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
DOSE LIMITS
 How much dose am I allowed to get?
 Dose is usually reported in rems or millirems (mrem).
MAXIMUM PERMISSIBLE DOSE FOR
OCCUPATIONAL WORKERS
Annual 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)
AND—Annual 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 extremity—50 rem (0.5 Sv)
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.
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.
MAXIMUM PERMISSIBLE DOSE
SPECIAL CASES (cont.)
 MINORS - Persons
Under 18 years old.
 0.5 rem for 52 weeks
 MEMBERS OF THE
PUBLIC
 100 mrem (1 mSv) for
52 weeks from
controlled sources of
ionizing radiation.
RADIATION SAFETY OFFICE
Dosimetry Program
The Radiation Safety Office issues
Personnel Dosimetry
About 850 Persons are badged at WSU.
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:
 Extremity badge:
 Pocket dosimeter:
Monitors whole body exposure to b, , X-ray
and neutrons.
Monitors exposure to hands or feet.
Direct reading instrument that monitors real
time whole body exposure.
Dosimetry Program
External dosimetry
 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
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.
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.
Dosimetry Do’s and Don’ts
 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.
Test Time!
 Follow this link to the test.
https://myresearch.wsu.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.