Selenium 75-based gammagraphy device for ionising radiation dose rate and scanning exclusion zone reduction in NDT operations
An innovative gammagraphy device has been developed to conduct Radiographic Testing inspection of girth welds on liquid oxygen conveying pipes connected to the Soyouz launch pad at the Kourou Space Center. This device provides enhanced protection for operators by reducing the ionising radiation dose rate whilst reducing the scanning exclusion zone.
The regulations applicable during the examination of a part or object using a portable ionising radiation emitting apparatus demand cordoning off of the operating zone with boundary markers. At the edge of the exclusion zone the average equivalent dose rate evaluated over the total duration of the operation, must remain less than 0.0025 mSv/h. This safety perimeter, whose access is restricted to personnel whose presence is essential (Category A), can reach major proportions.
In order to reduce this zone, the Gamma-Prox technology has been initially developed by the Institut de Soudure to be operated at the Kourou Space Center (French Guyana) on the Soyouz launch pad. This device provides enhanced protection for operators by reducing the ionising radiation dose rate whilst reducing the scanning exclusion zone. Under the same operating conditions (operating and exposure times), but using Selenium 75 source with Gamma-Prox, the radius of the exclusion zone is reduced to about 8 metres (this value is obtained using the optimised collimation system, and identical measurement conditions as those used above).
Presently used for NDT Applications in the Oil and Gas sector, this technology shows potentiel for other non space applications such as nuclear, power production or industry.
Innovations & Advantages
- Strengthening of security and protection operators and the public
- Reduction of the marking perimeter (from 2 to 15 m according to situation, activity and type of radio-element)
- Savings generated by improvement of coactivity
- Device adaptable to authorized gammagraphs
- Scalable system: new radio-elements, special applications ...
- Innovative system: patents filed by the Welding Institute
For example, an RT examination using a radioactive Iridium 192 source of 0.93 TBq (25 Curies) standard activity and for which the cumulative exposure times would be 2 hours for a total operation duration of 6 hours involves cordoning off an operating zone whose radius is equal to about 40 metres (this value is obtained using a 1/250th depleted uranium collimator, measured on its side – practical attenuation approximately 1/100th).
Current and Potential Domains of Application
Gamma-Prox is now a family of equipment and is currently being used mainly for Non-Destructive Testing Evaluation applications in the Oil and Gas market.
This technology can finds similar usecases in other non-space markets such as :
- Power Production
- Foundries (NDT on castings and molds for transportation for example)