Buying Iridium-192 (Ir-192) sealed sources for your gamma radiography source projector is an important purchase. It is the crucial element that makes gamma radiographs of pipelines, flanges, tanks, castings, and weldments possible. Ir-192 can affect your ability to perform gamma radiography reliably, quickly, and safely in field-based environments.
There is a lot of research to do before buying Ir-192 and many decisions you need to make. If you leap in without doing your homework, you could end up with the wrong activity and focal size for your application resulting in longer shot times and poor image quality.
Doing your research can help you make educated and informed decisions to ensure the Ir-192 you purchase makes sense for your specific application and works reliably and safely in your gamma-ray source projector.
7 questions to ask before buying Ir-192 sources:
- Why is Ir-192 preferred for gamma radiography?
- What is the difference between natural and enriched Ir-192 sources?
- What are the common Ir-192 activity range and focal spot sizes for gamma radiography?
- What factors impact the price of Ir-192 sources?
- What factors impact Ir-192 lead time?
- How are Ir-192 sources regulated and what do I need to be aware of?
- How do I dispose of my old Ir-192 sources?
Why is Ir-192 preferred for gamma radiography?
Note: Information in this section was drawn from the 2019 edition of the ASNT Handbook, Chapter 3 on Radiation Sources and Exposure Devices, written in 2001 by Mark Shilton, VP Technology, QSA Global, Inc. in conjunction with other contributors[1].
When Ir-192 decays, its principal gamma-ray emission energies are in the energy range from 296 keV to 612 keV. This range ideally matches the gamma-ray attenuation characteristics of many standard fixtures that have joints, such as pipelines, flanges, tanks, castings, and weldments.
Energy range, coupled with high specific activity and small focal spot sizes, makes Ir-192 the preferred choice for most gamma radiography applications. The practical working thickness range in copper, nickel, or steel alloys for Ir-192 is commonly accepted as 0.8 in-2.5 in (12-63 mm) (this may be variable depending on the sensitivity requirement and imaging methodology).
What is the difference between natural and enriched Ir-192 sources?
Note: Information in this section was drawn from the 2019 edition of the ASNT Handbook, Chapter 3 on Radiation Sources and Exposure Devices, written in 2001 by Mark Shilton, VP Technology, QSA Global, Inc. in conjunction with other contributors[1].
Natural Iridium
Typically offered in the marketplace as just ‘iridium,’ Natural iridium is the commonly available form of iridium which has 38% Ir-191 and 62% Ir-193. This is the same composition that you can see in commercially available iridium products like the rollerball in ballpoint pens.
The advantage of ‘natural’ iridium is its price, and it doesn’t have much processing before it goes into a reactor.
The downside is that the high level of impurities from Ir-193 makes for a much larger source volume and the undesirable isotope Ir-194. The good news is that when you receive an Ir-192 source, almost all of the Ir-194 has decayed away.
Enriched Iridium-192
Iridium of natural isotopic composition can be isotopically enriched by gas centrifugation to produce enriched iridium containing about 80% Ir-191 and 20% Ir-193. This means enriched iridium has a much higher probability of absorption and results in a much higher yield of Ir-192 sources than natural iridium.
Gamma radiography sources made from enriched iridium provide a better return on investment: sharper images reduce the time and cost of reshoots, faster shot times increase productivity, and the smaller focal increases the useful shelf life of your Ir-192 source.
- Reduce time and costs associated with reshoots. The smaller focal spot size of enriched Ir-192 reduces Geometric Unsharpness (Ug), which gives you a sharper, more acceptable image - even from your less experienced radiographers.
- Achieve faster shot times for small bore piping and profile radiography. A smaller focal allows you to achieve the required Ug with a shorter source to detector distance, resulting in faster shot times. Shorter shot times and more compact setups also minimize your potential radiation exposure.
- Increase the usable life of your source. When your 100 Ci source decays and no longer provides acceptable productivity for contact shots, you can still use it for offset configurations on small bore piping. A decayed enriched Ir-192 source will allow you to achieve the required Ug for these applications without increasing SFD and shot times.
The downside of using enriched Ir-192 for gamma radiography is that it is more expensive than natural iridium due to the additional processing required.
Small focal, enriched Ir-192 radiography sources were first introduced by QSA Global, Inc. in 2000.
What are the common Ir-192 activity range and focal spot sizes for gamma radiography?
Ir-192 sources range in activity up to about 240 Ci (8.88 TBq). They typically have a focal spot size in the range of:
- 0.091-0.181 in (2.31- 4.60 mm) for natural Ir-192
- 0.028-0.152 in (0.71-3.76 mm) for enriched Ir-192
What factors impact the price of Ir-192 sources?
Additional processing of raw materials
The additional processing of enriched iridium significantly increases the cost of the discs. Enriched iridium requires gas centrifugation to separate stable Ir-191 from stable Ir-193. The separated Ir-193 fraction is discarded while the enriched Ir-191 fraction is made into discs before irradiating in a nuclear reactor to make Ir-192 sources. Highly specialized plants must gasify and then separate the Ir-191 from Ir-193. These plants are similar to those used to separate U-235 from U-238 to produce nuclear fuel, and few are available to source the material.
Value-added services
When you order Ir-192, you may need to shell out extra money for:
- assistance with transporting your Ir-192 sources
- loading or reloading Ir-192 sources into your gamma-ray source projector
- retaining a container to store your Ir-192 sources until your next job
- disposing of Ir-192 sources you no longer require
What factors impact Ir-192 lead time?
Iridium is one of the scarcest elements on earth. The most significant factors impacting Ir-192 lead time are supply, demand, and a limited number of Ir-191 enrichment companies and high flux reactors that can produce high-quality Ir-192. When demand is greater than supply, it causes instability in the overall supply of Ir-192 and can significantly increase Ir-192 lead time.
QSA Global, Inc. mitigates supply chain instability by working with multiple reactors and has invested in supply chain and manufacturing facilities in the US, Europe, and Asia. We plan our inventory based on seasonal trends and market feedback so we can quickly react to user demand and reduce what would otherwise be very long lead times.
The transportation of radioactive materials is highly regulated. It is important to understand the rules and regulations required to transport radioactive sources around the world and how this impacts your lead time. We recommend working with a company that has thorough regulatory knowledge so they may assist you when transportation-related issues occur and provide regulatory support to keep you out of trouble.
No matter who you work with for obtaining your Ir-192 sources, we recommend you plan and reserve your Ir-192 in advance so you have it when you need it.
How is Ir-192 regulated and what do I need to be aware of?
Before ordering or using Ir-192 radioactive sources, or any other radioactive material, customers must ensure they are complying with their national or state regulations. In most countries, regulations are closely related to the International Atomic Energy Agency (IAEA) and U.S. Nuclear Regulatory Commission (NRC) rules and codes of practice.
If radiation sources are transported for use, it is necessary to refer to the regulations as listed on the approval certificate. Depending on the mode of transport, it is also necessary to comply with the regulations of ICAO, the International Civil Aviation Organization and the requirements of IATA, the International Air Transport Association, or IMO, the International Maritime Organization, or ADR, the European Road Regulations.
QSA Global, Inc. has well-established positive relationships with the IAEA and USNRC Regulatory Authorities and is recognized as the leader in the industry for the quality of our products and our expertise. Our excellent regulatory infrastructure allows us to conduct business safely and legally while helping you understand the rules and regulations in the countries and states where you are using Ir-192.
How do I dispose of old Ir-192 sources?
When you are working with radioactive materials, like Ir-192, it is important to consider what you need to do to properly dispose of them when they are no longer required. Radioactive materials that are no longer required must be transferred to a licensed recipient for final disposition.