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

1 / 21

# Radiation Safety Training Dose limits and Dosimetry Washington State University Radiation Safety Office - PowerPoint PPT Presentation

Radiation Safety Training Dose limits and Dosimetry Washington State University Radiation Safety Office. Units Used in Radiation Safety. erg. Rad . Sievert. Roentgen. joule. Curie. Rem. Gray. Becquerel. Units Definitions Really it’s not that hard. Energy. ft  lb, erg, joule,

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

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

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Radiation Safety TrainingDose limits and DosimetryWashington State UniversityRadiation Safety Office
Units Used in Radiation Safety

erg

Sievert

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:

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.

• 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.

1 Joule = 0.24 calorie

1 calorie=amount of energy to heat up 1 milliliter of water 1 degree C.

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)

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.

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).

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 DOSESPECIAL 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.
• MEMBERS OF THE PUBLIC
• 0.5 rem for 52 weeks
• 100 mrem (1 mSv) for 52 weeks from controlled sources of ionizing radiation.
RADIATION SAFETY OFFICEDosimetry 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: 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.

Dosimetry Program

External dosimetry

TLD Ring

Thermoluninescence dosimeter

Worn on index finger of dominant hand, with the white face turned towards the radiation source.

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