X-Ray Safety Training for Users of the Rigaku MiniFlex X-Ray Diffractometer in PRISM

This module contains the following sections:

• Introduction
• Section 1: Regulations
• Section 2: Radiation Basics
• Section 3: Biological Effects
• Section 4: X-ray Diffraction Hazards
• Section 5: Dose Limits
• Section 6: Using Radiation Monitoring Badges
• Section 7: Working Safely with the PRISM Rigaku MiniFlex XRD
• Section 8: Radiation Incidents
• Section 9: Final Step of X-Ray Safety Training

This X-Ray Safety module has been developed solely for users of the PRISM IAC Rigaku Miniflex x-ray diffractometer. Completing this training does not qualify you to use any other x-ray diffraction equipment at Princeton University. If you plan to use any other x-ray diffraction equipment at Princeton University, you must schedule a meeting with Sue Dupre.

Introduction

The Imaging and Analysis Center (IAC) at the Princeton Institute of the Science and Technology of Materials (PRISM) possesses a Rigaku Miniflex x-ray diffractometer for general use by Center users.

Before using the Rigaku Miniflex for the first time, each person:

The Princeton University Radiation Safety Officer is Sue Dupre, who is a member of the Environmental Health & Safety Office staff. Sue developed this online x-ray safety training program. Contact Sue with any questions or concerns about radiation safety in general, about this training, or about x-ray safety concerns related to the Rigaku Miniflex XRD.

Sue Dupre Phone: 258-6252

 

Section 1: Regulations and the Radiation Safety Program at Princeton University

The use of x-ray equipment is regulated by state governments rather than by the federal government. In New Jersey, it is the Radiation Protection Program of the New Jersey Department of Environmental Protection (NJDEP) which sets the standards for the use of x-ray equipment.

NJDEP regulations which pertain to x-ray diffraction equipment such as the Rigaku Miniflex XRD are contained in Chapter 7:28 of the New Jersey Administrative Code. These regulations can be viewed at the Radiation Protection Program's website.

• Subchapter 6 sets forth the allowable dose limits for radiation workers.
• Subchapter 21 of NJAC 7:28 sets forth the requirements for analytical x-ray equipment (NJDEP defines x-ray diffraction equipment as analytical x-ray equipment). This subchapter specifies what warning lights and notices must be present, what interlocks and other safety systems must be designed into the equipment, how often the safety systems must be tested, and specifies that x-ray users must be provided with radiation monitoring badges.

NJDEP requires that the following Notice To Employees be posted at locations where x-ray users may view it and read it. This Notice is posted at the IAC Facility near the XRD. Click on the image below to view it as a PDF file.

This Notice makes the following important points:

• Princeton University is responsible for complying with NJDEP regulations and for providing you with the information and the operating procedures that will allow you to use x-ray equipment safely.
• You are responsible for being familar with the applicable provisions of the regulations and the operating procedures and for complying with these provisions.
• You have a right to know your radiation exposure history. If you are unable to find out your dose history at any point through the dosimetry contact person at IAC, you may contact EHS to request your dose history.
• All radiation-producing equipment at the University is subject to periodic inspection by NJDEP.
• You have the right to report safety concerns or regulatory violations without fear of reprisal.

The Radiation Safety Program at Princeton University

The Office of Environmental Health & Safety administers the radiation safety program for all sources of ionizing and nonionizing radiation at Princeton University. With regard to x-ray equipment such as the Rigaku Miniflex XRD, EHS is responsible for:

• registering all x-ray equipment with the NJ Department of Environmental Protection;
• performing a radiation survey and compliance inspection when x-ray equipment is first installed, and when equipment is relocated or reconfigured in any way that affects radiation safety;
• performing an annual survey and inspection of each x-ray machine;
• providing radiation monitoring badges for x-ray users;
• providing x-ray safety training for x-ray users.

Sue Dupre is Princeton University's Radiation Safety Officer.

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Section 2: Radiation Basics

X-rays are known as ionizing radiation because x-rays possess sufficient energy to remove electrons from the atoms with which the x-rays interact.

There are three quantities primarily used for describing the intensity of an x-ray beam:

• Exposure
• Absorbed Dose
• Dose Equivalent

Exposure is a quantity describing how much ionization is produced (i.e., how many electrons are produced as x-rays or gammas create ionization) in air by gamma- or x-rays.  The unit of exposure is the Roentgen.

1 Roentgen (R) = 2.58 x 10^-4 Coulombs of charge produced per kg of air.

Limitations: Exposure applies only to x-rays and gamma rays and describes only the effect on air, not on tissue.

Absorbed dose is a quantity describing how much energy is deposited in a material by a beam of radiation and is not restricted to x-rays or gamma rays passing through air.  The unit of absorbed dose is the rad.

1 rad = 100 ergs of energy deposited in one gram of material

Limitations: Absorbed dose does not indicate the effectiveness of various types of radiation in causing biological harm. Different types of radiation may deposit the same amount of absorbed dose but produce different effects and different levels of damage.  For instance, charged massive alpha particles will interact more intensely and deposit energy over a shorter distance within a cell than uncharged massless gamma rays. Consequently, some radiations are more effective than other radiations at producing biological damage, even though equivalent amounts of energy are deposited overall. The quantity, dose equivalent, described in the next paragraph takes into account the abilities of differing radiations to cause damage.

Dose equivalent is a quantity derived by multiplying the absorbed dose by a quality factor (QF) which depends on the type of radiation being measured.  Consequently, dose equivalent does reflect the ability of each type of radiation to cause damage. The unit of dose equivalent is the rem.

• Dose equivalent = Absorbed dose x QF
• QF = 1 for gamma rays, x-rays and most beta particles

For the remainder of this module, references to radiation intensity and dose will be expressed in terms of rems or millirems.

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Section 3: Biological Effects of X-Rays

X-rays produced by x-ray diffraction equipment are too low in energy to be deeply penetrating. With x-ray diffraction equipment, skin effects are the effect of concern. There is no concern for genetic effects or prenatal radiation exposure for x-ray diffraction users.

Mechanisms of Damage (top)

Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionizing radiation causes atoms and molecules to become ionized or excited. These excitations and ionizations can:

• Produce free radicals.
• Break chemical bonds.
• Produce new chemical bonds and cross-linkage between macromolecules.
• Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).
• The cell can repair certain levels of cell damage. At low doses, such as that received every day from background radiation, cellular damage is rapidly repaired.

At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function.

Prompt and Delayed Effects

Radiation effects can be categorized by when they appear.

Prompt, acute effects include effects such as skin reddening, hair loss and radiation burns, which develop soon after large doses of radiation (hundreds to thousands of rems) delivered over short periods of time (seconds to minutes).

Delayed effects include effects such as cataract formation and cancer induction that may occur months or years after a radiation exposure.

Prompt Effects

The following information is adapted from the Acute Radiation Syndrome Fact Sheet for Physicians, published by the Center for Disease Control:

When the skin receives a high dose of radiation, the primary damage occurs to hair follicles, basal (dividing) cells of the outer skin layer, and small blood vessels.

When the basal cell layer of the skin is damaged by radiation, inflammation, erythema (skin reddening), and dry or moist desquamation (shedding of the outer layers of the skin) can occur. Also, hair follicles may be damaged causing epilation (loss of hair). Within a few hours after irradiation a transient and inconsistent erythema (associated with itching) can occur. Then, there may be a latent phase that lasts from a few days up to several weeks, when intense reddening, blistering and ulceration of the irradiated site is visible. In most cases healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis, decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue.

At doses in excess of two thousand rems, destruction of the skin occurs due to direct skin cell death, loss of basal cells, or reduced blood flow due to destruction of small blood vessels. Pain is associated with loss of the integrity of the skin because nerves can become exposed to the air, die due to loss of blood flow, or be affected by infection of the damaged skin.

The medical response to these acute effects involves administering drugs to prevent infection, to control pain and to improve blood flow, but in the case of tissue necrosis, it is generally necessary to resort to skin grafting or amputation of the necrotic portion.

The photos below show damage to the hands from high-dose x-ray exposure

The following table summarizes the effects and the threshold dose required to produce these acute effects:

Effect	Threshold Dose
Erythema (skin reddening)	300 - 500 rem
Temporary hair loss	300 - 500 rem
Permanent hair loss	700 rem
Transepidermal injury (skin burns)	1000 rem
Dermal radionecrosis (tissue death)	2000 - 3000 rem

Additional notes concerning prompt effects:

These acute effects will develop within hours, days or weeks, depending on the size of the dose. The larger the dose, the sooner a given effect will occur. For example, at doses of 300 rems, it may take 1-3 weeks for erythema to develop, but, at doses of thousands of rems, erythema may develop within hours to days.

These acute effects are limited to the site of exposure. For example, if a portion of the hand is exposed to a very large dose, skin reddening or burns is limited to the section of the hand that received the high dose.

Be aware that the skin does not have receptors that sense radiation exposure. No matter how large a radiation dose a person receives, there is no sensation at the time the dose is delivered. It has been reported that some people who have received large doses have felt a tingling in the skin. However, it is believed that the tingling is due to static charge at the skin surface rather than the direct sensation of radiation exposure.

Delayed Effects of Radiation Exposure (top)

Cataracts

• Cataracts, or clouding of the lens of the eye, are induced when a dose exceeding approximately 500 rems is delivered to the lens of the eye. Radiation-induced cataracts may take many months to years to appear.
• It is extremely unlikely to receive a substantial dose to the lens of the eye when working with the Rigaku Miniflex XRD. It would be very difficult to place one's head in a position near enough to the primary beam to receive a dose sufficient to induce cataracts.

Cancer

• Studies of people exposed to high doses of radiation (on the order of hundreds to thousands of rem) have shown that there is a risk of cancer induction associated with high doses. These studies demonstrate that cancer risk is linearly proportional to the dose in the high dose region.
  
• The specific type of cancer associated with low-energy x-ray exposure is skin cancer.
  
• Radiation-induced cancers may take 10 - 15 years or more to appear.
  
• There may be a risk of cancer at low doses as well. The following material discusses the risk of cancer at lower doses

The Process of Determining Cancer Risk (top)

Why cancer risks at low doses are uncertain

It has been difficult to estimate cancer induction risks, because most of the radiation exposures that humans receive are very close to background levels. At low dose levels of millirems to tens of rems, the risk of radiation-induced cancers is so low, that if the risk exists, it is not readily distinguishable from normal levels of cancer occurrence. In addition, cancers induced by radiation are indistinguishable from those that result from other causes.

Go to optional information about radiation-induced cancer risk studies

Cancer Risk Estimates (top)

Using the linear no-threshold risk model, the 1990 BEIR* V report provided the following estimate:

The average lifetime risk of death from cancer following an acute dose equivalent to all body organs of 0.1 Sv (10 rem) is estimated to be 0.8%. This increase in lifetime risk is about 4% of the current baseline risk of death due to cancer in the United States. The current baseline risk of cancer induction in the United States is approximately 25%. Another way of stating this risk:

A dose of 10 mrem creates a risk of death from cancer of approximately 1 in 1,000,000.

* The National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation (the BEIR Committee)

Go to optional information with a more detailed excerpt from the BEIR V report

Putting Risk into Perspective (top)

One way to look at risk is by considering the Relative Risk of a 1 in a million chance of death from activities common to our society:

• Smoking 1.4 cigarettes in a lifetime (lung cancer)
• Eating 40 tablespoons of peanut butter (aflatoxin)
• Spending two days in New York City (air pollution)
• Driving 40 miles in a car (accident)
• Flying 2500 miles in a jet (accident)
• Canoeing for 6 minutes (drowning)
• Receiving a dose of 10 mrem of radiation (cancer)

(Adapted from DOE Radiation Worker Training based on work by B.L. Cohen, Sc.D.)

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Section 4: X-Ray Diffraction Hazards and Dose Rates

Analytical x-ray equipment makes use of very narrow collimated x-ray beams of high intensity. Exposure of the skin to the primary x-ray beam may result in doses within fractions of a second that will result in severe radiation burns. These burns heal poorly, and on rare occasions have required amputation of fingers.

These low-energy x-rays are easily attentuated by air, so the intensity of the x-ray beam decreases very rapidly as the distance from the tube increases, but substantial doses are possible in any part of the primary beam.

Possible Radiation Intensity Near Analytical X-Ray Equipment
Location	Dose Rate
Primary beam at tube port	several thousand rems per second
Primary beam at end of 10 cm collimator	several hundred rems per minute
Scattered radiation near sample	hundreds of mrems per hour

For PRISM's Rigaku Miniflex x-ray diffractometer, no leakage radiation is measurable outside the cabinet which encloses the x-ray beam. Consequently radiation exposure is possible only if you are able to gain access to the primary beam within the cabinet while the x-rays are on and while the shutter is open.

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Section 5: Dose Limits

Annual Radiation Dose Limits (top)

The NJDEP has established dose limits which are based on recommendations from national and international commissions. The table below lists the limits set by the NJDEP:

New Jersey Dose Limits

As Low As Reasonably Achievable (ALARA) (top)

Since the current model of radiation-induced cancer risk assumes that there is a risk no matter how low the radiation dose, it makes good sense to minimize radiation exposure. The University follows the practice of keeping doses As Low As Reasonably Achievable (ALARA). This means that the University will work to keep doses as far below the dose limits as can reasonably be achieved.

To keep doses ALARA, EHS will investigate unusual or unexpected doses in an effort to address causes of unnecessary radiation exposure.

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Section 6: Using Radiation Monitoring Badges

NJDEP regulations require that any person operating the Rigaku Miniflex XRD must wear radiation monitoring badges. Monitoring badges can be requested by contacting EHS at 8-5294 or from the IAC Facility Manager.

How the Monitoring Badges Work (top)

Luxel Body Badges

The Luxel body badge contains a sheet of radiation-sensitive aluminum oxide sealed in a light and moisture proof packet. When atoms in the aluminum oxide sheet are exposed to radiation, electrons are trapped in an excited state until irradiated with a specific wavelength of laser light. The released energy of excitation, which is given off as visible light, is measured to determine radiation dose.

The packet contains a series of filters designed so that the energy and type of radiation can be determined. In order for the radiation type and energy to be determined, the dosimeter must be worn so that the front of the dosimeter faces towards the source of radiation.

Luxel body badges are among the most sensitive dosimeters commercially available. The minimum detectable dose is 1 millirem for x-rays and gamma rays.

Ring Badges

The ring dosimeter contains a small radiation-sensitive lithium fluoride crystal. When atoms in the crystal are exposed to radiation, electrons are trapped in an excited state until the crystal is heated to a very high temperature. The released energy of excitation, which is given off as visible light, is measured to determine radiation dose. This phenomenon is called thermoluminescence and dosimeters that use this principle are often referred to as TLDs (thermoluminescent dosimeters).

TLD dosimeters are slightly less sensitive than Luxel dosimeters. The minimum detectable dose for TLD ring dosimeters is 30 millirems for x-rays and gamma rays.

Wearing Monitoring Badges(top)

Body Badge

If you are issued a Luxel body badge, you will receive a gray plastic badge holder and a badge packet sealed inside a cellophane-type plastic bag. Remove the badge from the bag and snap it into the gray holder.

Wear your body badge on the part of the body between your neck and waist that is closest to the XRD.

Wear the badge so that the name tag faces out toward the source of radiation.

Ring Badge

Your ring badge should be worn so that the label is facing out from the side of the hand most likely to receive a radiation exposure.

We know that it is unlikely for you to receive any measurable dose while working with the PRISM Rigaku XRD. However, since you are required to wear monitoring badges whenever you use the XRD, you should be sure to wear the badges in the positions closest to the potential source of exposure. For instance, if you are loading samples within the XRD chamber, you must still wear your monitoring badges even if the x-rays are turned off. In that case, you should place the ring badge on the hand closest to the x-ray tube and position the ring so that the name label is turned towards the x-ray tube.

Guidelines for Monitoring Badge Use (top)

• Never share your badges or wear another person’s badges. Each badge is intended to be worn by only the designated person. If you discover that your badges are missing or damaged, notify EHS promptly. EHS can usually provide you with replacement badges within a couple of hours.
• Do not intentionally expose badges to radiation. Intentional tampering with badges is a very serious matter.
• No matter how curious you are, do not wear your badges when you receive a medical x-ray or other medical radiation treatment. Your badges are intended to document occupational dose, not medical dose.

Monitoring Badge Storage (top)

A rack for storing badges is provided in the PRISM IAC Facility. Store your badges there rather than at home or in your office.

Lost or Damaged Monitoring Badges(top)

If you lose, damage, or contaminate your badge, call EHS immediately for a replacement. EHS can generally provide you with a replacement badge within a few hours of your request. Do not borrow anyone else's badge.

Badge Exchange and Processing (top)

Badges are exchanged quarterly. You should expect to receive your new badges a day or two before the start of each calendar quarter. Snap the old Luxel body badge out of the gray holder and return just the badge itself. Keep the gray holder so that you can snap the new badge into it. Make sure that your old badges are available for collection on the IAC Facility badge board.

Wearing a monitoring badge is a serious matter, as it can reflect on your lifetime recorded dose. Therefore, it is important for EHS to be able to account for any missing or damaged badges. If your badges are not turned in on time or are lost, EHS is required to conduct an investigation to estimate your dose and will ask you to provide an accounting of your activities involving radiation sources during the period in which the badges should have been worn.

Emergency Processing (top)

If you believe that you may have received an unusual dose (if you may have placed your hand in or near the x-ray beam, for example), notify EHS immediately. Your badges will be returned for rapid emergency processing.

Dose Reports and How To Read Them (top)

After you return your monitoring badges, the badges are sent out to the badge service company for processing. EHS receives the dose reports several weeks after the end of a monitoring period and reviews the dose reports. EHS has established investigational levels at doses that are 10% or less of the federal and state dose limits. If a dose is reported that exceeds the investigational level, EHS will contact you to to determine whether the reported dose is likely to be accurate and to investigate the causes of the dose in an effort to minimize dose in the future.

After EHS finishes its review, your dose data is imported to a Princeton University website and formatted into a report that is only accessible to you. EHS will send you an e-mail to let you know that your latest dose report is now available for review. After you log in to the website, you'll be able to view a report which will look much like the following report:

A summary of your badge results can also be obtained by calling EHS.

In the case of body badges, doses are reported as deep or shallow or as doses to the lens of the eye. Deep dose is due to penetrating radiations such as gamma rays or higher energy x-rays. Deep doses are applied against the whole body dose limit. Shallow dose is due to less penetrating radiations such as beta radiation and low energy x-rays. Shallow doses are applied against the skin dose limit. Dose to the lens of the eyes is due to an intermediate range of radiations and energies and is applied against the lens of the eye dose limit.

In the case of ring badges, dose is only reported as shallow dose and is applied against the extremities dose limit.

Doses are reported in millirems. The minimum reportable dose for x-rays for body badges is 1 millirem for x-rays, and for ring badges is 30 millirems. If a dose of "M" is reported, the total dose received was minimal, i.e., less than the minimum reportable dose.

Exposure History (top)

Contact EHS for a copy of your radiation exposure history. EHS maintains radiation exposure records indefinitely.

If you terminate employment with the University, your radiation exposure history will be provided to you or your new employer upon request. A signed release statement must accompany any request from your new employer. Requests for radiation exposure histories should be mailed to: EHS, 262 Alexander Street, Princeton, NJ 08544

Radiation Use at Other Institutions (top)

Do not take Princeton monitoring badges to any other institution. Princeton University badges are intended solely to measure the radiation dose you receive while working at Princeton University. If you perform radiation work at another institution, it is the responsibility of that institution to provide you with monitoring badges.

However, Princeton University must still control the dose you receive while working at Princeton so that your total occupational dose does not exceed state dose limits. If you are issued radiation monitoring badges at any other institution, notify EHS immediately. EHS will contact that institution and request copies of your dose records.

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Section 7: Working Safely with the Rigaku Miniflex XRD

The Rigaku Miniflex XRD operates in a more limited way than many other XRDs. For example, the high voltage and current are preset at 30 kV and 15 mA, respectively. Also users of the Rigaku Miniflex XRD do not perform beam alignment. Work within the sample chamber is limited to sample placement. These limited options and the safety features that are built into the Rigaku Minflex XRD mean that the radiation hazards associated with use of this XRD are more limited. However, you must always be aware that, should you be able to gain access to the primary beam, it is readily possible to receive high doses to the hand that could result in permanent skin damage.

EHS conducted an initial radiation survey and compliance inspection when the Rigaku Miniflex XRD was moved to its current location, and EHS conducts an annual radiation survey and inspection of this unit. For PRISM's Rigaku Miniflex XRD, no leakage radiation is measurable outside the cabinet which encloses the x-ray beam. Consequently radiation exposure is possible only if you are able to gain access to the primary beam within the cabinet while the unit is producing x-rays and while the shutter is open.

In order to allow you to work safely with x-ray diffraction equipment, NJDEP has established the following requirements for XRDs:

 

Any opening in the enclosure must be interlocked to prevent access to the primary beam. In the case of the Rigaku Miniflex XRD, the sliding panel which opens into the interior of the XRD is interlocked with the x-ray shutter. If the panel is opened, the x-ray shutter closes automatically.

Be aware that it is possible for the shutter to fail so that it does not close or does not close completely.

To protect yourself from the possibility of shutter failure, it is a requirement for the Rigaku Miniflex XRD that you must turn off high voltage before you open the panel.

Turn off high voltage to the x-ray tube before opening the panel!

The next photo shows the interior of the sample chamber:

Always check the shutter status light on the control panel, even if you are certain that you turned off the high voltage.

Testing the Safety Systems

NJDEP requires that the safety systems such as the panel interlock be tested every six months. A member of the IAC staff is responsible for conducting the semiannual tests.

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Section 8: Radiation Incident Response

If you believe that you have placed any part of your body in or near the primary beam, for example, if you discovered that the shutter was open while your hands were inside the sample area:

Immediately call

• EHS at 258-5294 (during normal work hours)
• Public Safety at 258-3134 (outside of normal business hours). Public Safety will be able to contact an EHS staff member.

Do not hesitate to call no matter what time of day the incident has occurred.

EHS will take the following actions:

Ship your radiation monitoring badges off for emergency processing.

Arrange for you to visit McCosh Health Center once a day to have the condition of your hands monitored until the period of concern has passed.

Estimate the amount of dose your hands received by asking you to re-enact the incident (without the x-rays on, of course!). EHS will determine the position of your hands relative to the beam, will measure the amount of time your hand was in or near the beam path and will place radiation dosimeters at the position of your hand in order to estimate the dose received.

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Section 9: The Final Step of X-Ray Safety Training

In order to complete x-ray safety training for the PRISM Rigaku Miniflex XRD, you must:

• Review this entire x-ray safety training module
• Click on the link below to fill out and find out how to submit the X-Ray Safety Training Certification Form to EHS

After EHS receives the Training Certification Form, EHS will notify the IAC Facility Manager that you are eligible to complete x-ray operations training. The IAC Facility Manager will provide you with a set of radiation monitoring badges at the time of operations training.

Completing this training does not qualify you to use any other x-ray diffraction equipment at Princeton University. If you plan to use any other x-ray diffraction equipment at Princeton University, you must schedule a meeting with Sue Dupre.

Complete the X-Ray Safety Training Certification Form to demonstrate that you have completed this x-ray safety training module. Email the completed Form to dupre@princeton.edu

• Go to X-Ray Safety Training Certification Form

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