Post on 01-Apr-2015
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Radiological & Environmental Management
Purdue University
Sealed Source Safety Retraining
Updated 09/2012
Basic Radiation Safety Principles Familiarization with Regulations Purdue’s Policies and Procedures
Training Goals
Radioactivity is an energy This energy is produced when an unstable nucleus
spontaneously emits particles and/or electromagnetic radiation
Radioactive material sources Sources are characterized as either sealed or
unsealed (or “open”) To qualify as a “sealed” source, the source must
pass a battery of stress tests and be certified under NRC regulations
What is radioactivity?
Sealed Source
Means any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material (USNRC
Regulations 10CFR30.4)
Definition
Pictures of common sealed sources
Alpha Molecularly large particle (2 protons and 2 neutrons), give
up their energy in a short distance (approximately 1 ½ inches in air)
Beta Smaller particle (electron), distance traveled ranges from
several inches to a few feet (depending on its energy) Gamma
Non-particulate energy wave, can travel several feet and easily penetrates material with low atomic mass
Neutron Neutral particle, can travel greater distances than gamma
radiation and easily penetrate material with low hydrogen ion concentrations
Ionizing Radiation Types
An average person in the United States receives annual radiation dose of ~620 mrem, which includes exposure received from cosmic and natural radiation, medical treatment, and consumer products.
Large doses of radiation have been known to increase risk of cancer, birth defects, and possibly genetic effects.
Low doses seem to show no statistical differences in biological risk; however, some people believe there is risk at all levels above background exposure.
At radiation levels around 1 rem, it has been estimated that the increased incidence of cancer is 0.03% - the normal incidence of cancer for the average person is 25%.
Risk of developing genetic effects is half the risk of cancer.
Risks of Radiation Exposure
Contamination Control gloves, lab coats, fume hoods, absorbent paper
Time do dry run, practice procedure to minimize time
Distance a little distance between you and a source can
significantly decrease your exposure from it (follows the “Inverse-Square Law”)
Shielding Use proper shielding between you and a source to
decrease personal exposure betas - wood, Plexiglas (do NOT use lead) gammas - lead, leaded glass
4 Factors to Reduce Exposure
Click here for a sample calculation
21
22I1d = I2 d
Point Sources The intensity of radiation decreases as the inverse
square of the distance. Doubling distance, exposure = ¼ of original;
Tripling distance, exposure = 1/9 of original.
Inverse Square Law
(I1)(d1)2 = (I2)( d2)2
(20 mR/hr)(1ft)2 = (I2)(2ft)2
(20 mR/hr)(1ft)2 = I2
(2ft)2
(20 mR/hr)(1ft2) = I2
(4ft2)
I2 = 5 mR/hr
I1 = 20 mR/hr
I2 = ??
d1 = 1 ft
d2 = 2 ft
Sample Calculation
Inverse Square Law - Diagram
Different shields are needed to minimize external exposure
Ionizing Radiation Shielding
Radioactive material use must be licensed by the United States Nuclear Regulatory Commission (USNRC) or state agency. In Indiana, the USNRC is the regulating body.
Radiation Safety Officer (RSO) develops and maintains a Radiation Safety Manual, which must be followed by individuals working under the NRC license, and it is enforceable by law
Purdue University’s Radiation Safety Committee (RSC) also oversees and governs the radiation safety program.
Rules Governing Use of Radionuclides
10CFR19 Rights and responsibilities of radioactive material
licensees are outlined. 10CFR20
Standards for protection against radiation: this discusses issues such as procedures and regulatory limits Declared pregnant worker Security of radioactive materials
Regulations
Rights to be informed of storage, transfer, and use of
radioactive materials to further instruction on health protection
problems associated with radiation exposure and procedures to minimize exposure
to receive radiation exposure history to request an NRC inspection to be instructed in and required to observe
applicable provisions of NRC regulations and licenses
to be instructed in the appropriate response to warnings
10CFR Part 19Instruction to workers
Retaliation against employees or students engaged in protected activities, whether they have raised safety concerns within the University or to the NRC, will not be tolerated
Problems should be addressed within the existing University hierarchy – contact the radiation safety office if you have any concerns regarding issues involving radioactive materials.
NRC Policy Statement
Occupational dose limits Surveys and monitoring Precautionary procedures Waste disposal Records of surveys Enforcement Storage and control of licensed material
10CFR20
All dose limits include exposure from both internal and external sources.
Target Dose Limit
Whole Body 5 rem/yr
Organ or Tissue 50 rem/yr
Skin or Extremities 50 rem/yr
Lens of Eye 15 rem/yr
Minor (i.e. non-adult) 10% of adult limits
Declared Pregnant Worker 0.5 rem per 9-month gestation period
10CFR20Occupational Dose Limits
If a worker wishes to declare her pregnancy, she must declare it in writing to the Radiation Safety Officer.
A declaration of pregnancy is entirely voluntary, and can be withdrawn at any time – no reason needs to be given.
For a worker wishing to declare her pregnancy, she should contact REM for Declared Pregnant Worker Training, which covers important information, and provides her the declaration form she needs in order to declare her pregnancy. REM will also provide a fetal dosimeter at the time of declaration, assuming that it is warranted by the type of radiation that has the potential for exposure to the worker.
The dose limits will be reduced from 5 rem per year to the worker, to 0.5 rem to the fetus for the 9-month gestation period (this is for both external and internal exposure)
Regulatory Guide 8.13Prenatal Exposure
Exposure= ability of photons to ionize air Roentgen (milliroentgen, mR) Geiger-Mueller readings
Absorbed Dose= energy deposited in matter Rad (millirad, mrad)
Dose Equivalent= biological weighted absorbed dose (tissue) rem (millirem, mrem) these units are what film badge (dosimetry)
results are reported
Radiation Units
Non-stochastic: Until a minimum exposure level is reached, there is no
biological effect. Once that minimum exposure level is exceeded, the
biological effect grows proportionally with the exposure. The Lethal Dose to 50% of the population (LD50) is about
600 rad Examples of biological response (effects) from
radiation erythema (skin reddening) blood changes (marrow depression is seen at
approximately 200 rad) Gastrointestinal Syndrome (severe vomiting, diarrhea) –
happens at approximately 1000 rad, and death is a likely outcome.
Acute Effects of Radiation Exposure
Stochastic (occur by chance, statistical basis) No threshold, but as the dose increases, the
probability of the effect also increases Examples of stochastic effects: may be seen 5
to 20 years after the exposure Cancer Leukemia Cataracts Life Shortening
Data extrapolated from high dose data (early radiology, Hiroshima/Nagasaki bombing, Chernobyl nuclear plant fire)
Delayed Effects of Radiation Exposure
High doses - there is a correlation between dose and effect
Low doses (<10 rem) - it is unclear what the risk is at this level difficulty performing long-term studies on effected
people, while eliminating other factors (e.g. did the radiation worker get cancer from her work, or that she smoked cigarettes, or that she was genetically programmed that way)
Hormesis – this is a theory that low doses of radiation may actually be beneficial
Risk Analysis
You can use Geiger-Mueller Survey instrument for detection of higher-energy beta and gamma sources.
REM will be conducting “leak tests” on sealed sources to evaluate whether the source containment is intact this will be done at timely intervals.
Survey work areas, floors around work areas and any doors, lab coat, hands, shoes, if it is felt that the source integrity has been compromised (e.g. dropped, smashed, had acid spilled on it)
Record survey results, maintain records for 3 years
Surveys
Secure laboratories when unoccupied (if this is not feasible, secure the radioactive material)
Challenge visitors or unauthorized individuals REM accounts for RAM through inventory
records Assume only you are approved for the type of
materials you are using. If another group wants to borrow them, you must ALWAYS check with the radiation safety office before relinquishing control of the material.
SecurityNRC Area of Emphasis
Call 911 Assist personnel if injured Monitor personnel if contamination is
suspected Control area - inform other personnel of the
situation and advise them not to enter Notify radiation safety office, once emergency
personnel are en route
Emergency Procedures
Medical needs come first! Postpone monitoring, call 911, notify of radioactive material use
Wait for medical personnel - calmly advise radioactive materials may be involved
Trained radiation worker may need to accompany patient to treatment center.
Notify REM
Severe Personal Injury
Always use ALARA No eating, drinking, or smoking in labs Always secure materials, lock doors Never allow unauthorized users access to
radioactive materials Call REM for any related questions (49-46371) All Emergencies – call 911
Review
James F. Schweitzer, Ph.D. 49-42350Radiation Safety Officer jfschweitzer@purdue.edu
Zachariah C. Tribbett 49-41478Health Physicist ztribbet@purdue.edu
Sharon K. Rudolph 49-47969Isotope Ordering & Distribution skrudolph@purdue.edu
Jerry J. Gibbs 49-40207Waste Handling & Meter Calibration jjgibbs@purdue.edu
Mike Nicholson 49-40205Waste Handling & Animal Hospital Support mlnicholson@purdue.edu
REM Main Office 49-46371Civil Engineering Building, Room B173www.purdue.edu/rem
REM’s Radiation Safety Group
Complete the test indicated below. You must have a minimum score of 75% to pass.
Your results will be sent to you through email, and, if you have passed, will be the documentation you would use to prove certification for renewal.
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