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When X-ray radiation from the handheld XRF (pXRF) excites atoms in the sample, the atoms release fluorescent X-rays. The energy level of each fluorescent X-ray create created is characteristic of the element excited; as a result, one can tell what elements are present. The Olympus Delta Bruker Tracer 5 pXRF detects and determines the fluorescent X-ray energies produced. As the pXRF emits radiation (from 8-40keV4 to 50 kV), a comprehensive knowledge of radiation safety and procedures is needed.
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The term radiation is used with all forms of energy: light, X-rays, radar, gamma rays, microwaves, and more. For the purpose of this manual, radiation refers to invisible waves or particles of energy emitted from a radioactive source or any X-ray tube. Radiation Radiation if received in too large a quantity, can have an adverse health effect on humans. There are two distinct types of radiation: non-ionizing and ionizing radiation.
Non-ionizing Radiation
Non-ionizing radiation does not have the energy necessary to ionize an atom (i.e., to remove electrons from neutral atoms). Sources of non-ionizing radiation include light, microwaves, power lines, and radar. Although this type of radiation can cause biological damage, such as a sunburn, it is generally considered less hazardous than ionizing radiation.
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Ionizing radiation has enough energy to remove electrons from neutral atoms. Ionizing radiation is of concern due to its potential to alter the chemical structure of living cells. These changes can alter or impair the normal functions of a cell. Sufficient amounts of ionizing radiation can cause hair loss, blood changes, and varying degrees of illness.
There are four basic types of ionizing radiation, emitted from different parts of the atom (see Figure Fig.1, below):
- Alpha particles
- Beta particles
- Gamma rays and X-rays
- Neutron Particles
Figure 1. Types of ionizing radiation and their atomic sources
The penetrating power for each of the four basic radiations varies significantly (Fig. 2).
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Figure 12. Types of Ionizing Radiation and Their Sources
Radioactivity-Emitting Materials
Some materials are inherently radioactive, such as the 1 micro-Curie 60Co sources used to calibrate the natural gamma radiation multisensor logger (NGRL) in the Physical Properties laboratory. Not only do they emit radiation (which can be ionizing or non-ionizing, and present direct hazards), but they could also theoretically be ingested, injected, or inhaled.
Alpha and beta particles have little ability to penetrate the skin, so alpha- and beta-radiation sources are most dangerous when they are taken into the body; this is called radiation poisoning. X-ray, gamma ray, and neutron sources are able to penetrate the skin, so the risk is both direct (radiation burn or acute radiation exposure) and indirect (radiation poisoning).
Radiation Producing Devices
Penetrating power of the four basic radiation types.
Alpha and beta particles have little ability to penetrate the skin, so alpha- and beta-radiation sources are most dangerous when they are taken into the body; this is called radiation poisoning. X-ray, gamma ray, and neutron sources are able to penetrate the skin, so this external risk is both direct (radiation burn or acute radiation exposure) and indirect (radiation poisoning).
Radiation Producing Devices
The pXRF is a radiation producing device (RPD); X-rays are generated by a cathode-ray tube. If current is applied to the tube in sufficient voltage (>4 kV) In the case of the pXRF, the X-rays are generated by a cathode-ray tube. If current is applied to the tube in sufficient voltage (>8 kV) to generate X-rays, radiation is produced. If no current is flowing, no radiation is produced. Therefore, the pXRF is completely safe from a radiation standpoint when it is unpowered.
Note: the The Bruker Tracer 5 pXRF emits only X-rays. For this reason, this manual will preferentially focus on x-rays from this point on.
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- Electromagnetic waves or photons of pure energy that have no mass or electrical charge
- X-rays are emitted from the inner electron shells of atoms, or from an RPDa radiation producing device
- Ionize atoms by interacting with electrons
Distance
Because X-rays (and gamma rays) have no charge or mass, they are highly penetrating and can travel quite far. Range in air can easily reach several hundred feet. Figure 2 reflects this graphically.
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Shielding
X-rays interact with matter and lose energy because of that interaction. Therefore, the best shielding materials are dense, such as concrete, steel, or lead.
Hazard
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Biological Effects of Radiation
Cell
Biological Effects of Radiation
Cell Sensitivity
The human body is composed of over 50,000 billion living cells. Groups of these cells make up tissues, which in turn make up the body's organs. Some cells are more resistant to viruses, poisons, and physical damage than others. The most sensitive cells are those that are rapidly dividing. Radiation damage may depend on both resistance and level of activity during exposure.
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Using other occupational risks and hazards as guidelines, nearly all scientific studies have concluded the risks of occupational radiation doses are acceptable by comparison. By learning to respect and work safely around radiation, we can limit our exposure and continue to enjoy the benefits it provides.
Table 1a and 1b., below summarize the risks associated with various activities; note the low loss associated with occupational radiation exposure (when proper controls are in place).
Table 1a (left) and 1b (right). Average estimated days lost by occupation and daily activities.occupational radiation exposure (when proper controls are in place).
Radiation Dose Limits
To minimize the risks from the potential biological effects of radiation, the state health departments and the Nuclear Regulatory Commission (NRC) have established radiation dose limits for occupational workers as shown in Table 2a and 2b, below.. The limits apply to those working under the provisions of a specific license or registration.
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Table 2a (left) and 2b (right). Typical radiation doses from selected sources and average occupational doses.
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Type of Body Area | Description | Allowable Limit (rem/year) |
Whole Body | The whole body is measured from the top of the head to just below the elbow and just below the knee. The limit is the sum of both internal and external exposure | 5 |
Extremities | The hands, arms below the elbows, the feet, and legs below the knees | 50 |
Skin | The entirety of the skin | 50 |
Organs or Tissues | All organs and tissues, including the brain | 50 |
Lens of the Eye | The cornea (the internal eye and retina are included in organs or tissues) | 15 |
Declared Pregnant Worker | If a worker declares their pregnancy (formally and in writing), their radiation exposure limits are reduced by a factor of 100; the exposure limit for the embryo/fetus is as shown | 0.5 |
Table 3: Dose Limits by Body Area
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Several devices are employed for measurement of radiation doses, including ionization chambers, Geiger-Mueller tubes ("Geiger counter"), pocket dosimeters, thermoluminescence devices (TLD's), optically stimulated luminescence dosimeters (OSL) and film badges. On the ship, the JRSO has Geiger counters and film badges.
The Geiger-Mueller Tube
(OSL) and film badges. On the ship, the JRSO has an ion chamber, film badges and finger rings.
Ion Chamber
An ion chamber is the simplest detector for measuring radiation. It consists of a cylindrical chamber filled with air and a wire running through its center with voltage applied between the wire and outside of the cylinder. When radiation passes through the chamber, ion pairs are extracted and build up a charge. This charge is used as a measure of the exposure received. This measurement, however, is not as efficient or sensitive as a traditional Geiger CounterThe Geiger-Mueller (GM) Tube is very similar to the ion chamber, but is much more sensitive. The voltage of its static charge is so high that even a very small number of ion pairs will cause it to discharge. A GM tube can detect and measure very small amounts of beta or gamma radiation.
Dosimeters
These are two common types of dosimeters: whole body and extremity
Film Badge (Whole Body
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Dosimeter):
A whole body dosimeter is used to measure both shallow and deep penetrating radiation doses. It is normally worn between the neck and waist.
Finger
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Ring (Extremity Dosimeter):
A finger ring a film dosimeter in the shape of a ring, which is worn by workers to measure the radiation exposure to the extremities. Finger rings are the appropriate tool for pXRF use, since the hands are the most likely body part to be in proximity to the X-ray source.
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Natural and man-made background radiation is ubiquitous, providing an average annual radiation dose of 0.360 rem to every U.S. citizen. Large fluctuations in background radiation, by geographical location, have not been shown to result in any measurable increase in risk of any health effect. Nevertheless, any radiation dose received occupationally would be in excess of the background radiation dose received and can therefore be assumed to carry with it additive risk of deleterious effect.
State and federal regulations therefore establish a system of dose limitation and minimization. Individual doses are limited to ensure that deterministic effects (such as cataracts) are avoided and that total lifetime risks of stochastic effects (such as cancer and hereditary effects) do not exceed overall health risks for those persons working in safe industries. However, regulations also require that licensees further minimize radiation doses to individuals and to groups of individuals to the extent practical, social, economic and technological factors taken into account.
This concept or philosophy is given the special name ALARA which is an acronym for As Low As is Reasonably Achievable As Low As is Reasonably Achievable. That is the safety standard for working with all types of radioactive sources and radiation-producing devices, and it means that exposure should be as low as possible, within a reasonable limit.
While dose limits and administrative control levels already help ensure very low radiation doses, it is possible to reduce these exposures even more. The main goal is to reduce ionizing radiation doses to a level that is ALARA. There are three basic practices to maintain external radiation:
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The first method of reducing exposure is to limit the amount of time spent in a radioactive area: the shorter the time of exposure, the lower the amount of exposure.
The effect of time on radiation could be stated as:
Dose = Dose Rate X Time
This means the less time you are exposed to ionizing radiation, the smaller the dose you will receive, directly proportional to the time of exposure. Half the time means half the dose, and vice versa.
Distance
The second method for reducing exposure is by maintaining the maximum possible distance from the radiation source to the operator or member of the public. The principle of distance is that the exposure rate is reduced as the distance from the source is increased; as distance is increased, the amount of radiation received is reduced.
This method can best be expressed by the Inverse Square Law, graphically represented below in Figure 3. The inverse square law states that doubling the distance from a point source reduces the dose rate (intensity) to ¼ of the original. Tripling the distance reduces the dose rate to 1/9 of its original value.
C X (D1)2/ (D2)2 = I
C = the intensity (dose rate) of the radiation source
D1 = the distance at which C was measured
D2 = the actual distance from the source
I = the new level of intensity at distance D2 from the source
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The inverse square law does not apply to sources of greater than a 10:1 ratio (distance: source size), or to the radiation fields produced from multiple sources.
Shielding
The third (and most important) method of reducing exposure is shielding. Shielding is generally considered to be the most effective method of reducing radiation exposure and consists of using a material to absorb or scatter the radiation emitted from a source before it reaches an individual. Different materials are more effective against certain types of radiation than others. The shielding ability of a material also depends on its density, or the weight of a material per unit of volume.
Although shielding may provide the best protection from radiation exposure, there are still several precautions to keep in mind when using the Olympus Delta Handheld XRF:
- Persons outside the shadow cast by the shield are not necessarily 100% protected. Note: All persons not directly involved in operating the XRF should be kept at least three feet away.
- A wall or partition may not be a safe shield for persons on the other side. Note: The operator should make sure that there is no one on the other side of the wall.
- Scattered radiation may bounce around corners and reach an individual, whether directly in line with the test location or not.
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The pXRF analyzer generates spectrum data by analyzing the specific X-ray energies that get are scattered back to the detector. Because the X-rays travel in all directions, it is possible for an X-ray to miss the detector and be scattered in the direction of the operator. This is referred to as backscatter.
Although the XRF pXRF is specifically designed to limit backscatter reaching the operator, there is always the possibility that a small number of X-rays may scatter beyond the detector. In the case of light or thin samples that do not contain the main beam, the main beam may then be scattered back towards the operator. In this case, a shield around the sample should be used.
Important! Section halves should be measured using the shielded plastic holder. Discrete samples, including powders mounted in plastic cups, should only be analyzed in the Olympus pXRF Test Stand. The walls of the Test Stand are lead-lined. When the pXRF is secured in the Test Stand and the lid is closed, the radiation emission is considered negligible.
using the small stage with the shielded cup or using the benchtop chamber whenever possible.
Radiation Profile
To ensure safe operation of the system, it is vital that the operator understand the radiation field. The Radiation radiation profile contains measurements of the radiation field. The profile should be studied carefully by anyone that operates the handheld XRFpXRF, in order to better understand and apply the practices of ALARA doses (using time, distance and shielding).
Radiation Profile
Figure 4, below, states the Olympus DELTA Series Bruker Tracer 5 pXRF measured doses of scattered radiation, based on pXRF target and position.
Figure 4. Olympus DELTA Series Measured Doses Chart
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Bruker Tracer 5 pXRF Radiation Profile
pXRF Analyzer Safety Features
To control X-ray emissions, and thereby minimize the possibility of accidental exposure, the Olympus Bruker Tracer 5 pXRF analyzer has a multiple standard safety interlock structure consisting of two features listed below. Be sure to understand the software trigger lock setting to understand whether the trigger is "armed" or not.
Software proximity sensor
Within two seconds of starting a test, the analyzer detects if a sample is in front of the measurement window. If no sample is detected, the test aborts to prevent accidental exposure. Upon an abort action, the filter wheel returns to the 0 position, the X-rays shut off (the tube current decreases to 0.0 µA), and the red light stops blinking. If the probe is pulled away from the sample while a test is in progress, testing will stop and X-rays will shut off.
Software trigger lock
After a five-minute lapse between tests (default time), the trigger automatically locks. The pXRF analyzer also has a dead man trigger protocol, in which the user is required to pull and hold the trigger for the duration of the test. Releasing the trigger prematurely will abort the test.
Indicators and Alarms
X-ray Indicator
. Be sure to understand how these safety features work before operating the device.
Software Password Protection
Once powered on, the requires a password be entered. This prevents the operation or generation of x-rays without a valid password. The password is only shared with authorized individuals trained in the operation of the Tracer. The x-ray will not arm unless the operator is logged into the software via the touch screen, or if using the laptop connection, through Bruker RemoteCtrl software application. Additionally, after five-minutes of inactivity, the Tracer's software automatically times out and logs out the user (whether using the Tracer itself or Bruker RemoteCtrl). This will disarm the x-ray tube until the operator logs back in.
X-ray Warning
Once the password is successfully entered, an X-ray radiation warning is displayed. The operator cannot generate X-rays without pressing and releasing the trigger to acknowledge this statement.
Indicator Lighting
Lights indicate to An X-ray indicator alerts the operator when the tube is receiving power and when X-rays are emitted from the analyzer through the measurement window. The X-ray indicator is located on the upper rear portion of the analyzer. This indicator consists of a six-element red LED array, and has three states:
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lights are located along a light bar just below the rail on the top of the device.
No indicator lights visible
This signifies that the X-ray tube is disabled, disarmed and that there is no possibility of radiation exposure to you or bystanders. The instrument can be carried or set down safety safely in this condition.
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This also indicates the trigger is not active.
Orange indicator light
Solid red LED array. This signifies that the X-ray tube is enabled, and that there is no radiation exposure to you or bystanders. The instrument can be carried or set down safety in this condition.
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Red indicator light flashing
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In addition to the orange indicator light, red lights will flash along the light bar beneath the rail when the device is measuringBlinking red LED array. This signifies that the Xx-ray tube is powered on and that the analyzer is emitting Xactively emitting x-ray radiation through the measurement window. In this condition, the analyzer must be pointed toward a test sample and never at a human being.
Audible Alarm Protocol
Infra-Red Sensor
The Tracer has aninfrared sensor next to the measurement window that detects the presence of an object in front of the measurement window. X-rays can only be generated if the sensor detects an object.
Backscatter Detector
During each measurement, As a warning, the audible signal emits three tones when the X-ray tube is about to emit X-rays. During the subsequent testing period, the audible alarm maintains a "chirping" signal throughout the duration of the test. This feature is mandatory.
Infra-Red Sensor
The pXRF has an infrared sensor that detects the presence of an object in front of the pXRF source. If no object is detected, the pXRF will not activate the source.
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count-rate is continuously monitored. If the count-rate drops below the allowable threshold, as it would in the absence of a sample, X-ray generation is discontinued, minimizing potential exposure. If the device is pulled away from the sample while a test is in progress, testing will stop and X-rays will shut off.
Warning Labels
Warning labels identify the analyzer as a radiation producing device. The manufacturer's plate underneath contains regulatory information. Do not tamper with or remove these labels.
Radiation Safety Tips and Precautions
All operators should follow minimum safety requirements discussed below. When handled properly, the amount of radiation exposure received from the pXRF will be negligible. However, the following safety tips are provided to help ensure safe and responsible use:
- Prior to using the instrument, undertake radiation safety training and proper operation of the Tracer.
- WARNING: No one but the operator should be allowed to be closer than 3 feet from the pXRF, particularly the beam portmeasurement window. Ignoring this warning could result in unnecessary exposure.
- WARNING: The operator should never defeat the IR infra-red sensor in order to bypass this part of the safety circuit. Defeating this safety feature could result in over-exposure of the operator.
- Do not allow anyone other than trained personnel to operate the pXRF.
- Be aware of the direction that the X-rays travel when the red light is on and avoid placing do not place any part of your body (e.g., eyes, hands) near the X-ray port measurement window to stabilize the instrument during operation.
- Never hold a sample up to the X-ray port measurement window for analysis by hand; hold the instrument to the sample.
- Establish a no-access zone at a sufficient distance from the instruments measurement window, which will allow air to attenuate the beam.Enclose attenuate the beam working area with protective panels (e.g., >3.0 mm stainless steel. Ideally, this is at least 1 meter (3ft).
- Wear an appropriate dosimeter (see the Laboratory Officer for more information on when issue of a dosimeter is called for).
- The operator is responsible for the security of the handheld XRFBruker Tracer 5 pXRF. When in use, the device should be in the operator's possession at all times (i.e., either in direct sight or a secure area). Do not leave the device without first logging out of the device software.
- Always store the instrument in a secure location when not in use.
- During transport to and from the set up location, store the instrument in a cool, dry locationits designated, cushioned, Pelican case.
- WARNING: Pregnant women should not use the pXRF or work in proximity to it. See'Additional Note, : Pregnancy', above, for more information. Radiation exposure can be harmful to an embryo or developing fetus!
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