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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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