Metrology for decommissioning nuclear facilities

The first generation of nuclear power plants are due for decommissioning, a process that is expected to cost 150 billion Euro and will generate large volumes of highly radioactive waste. Highly contaminated graphite, concrete, and steel require in-situ identification followed by removal and accurate segregation to ensure safe and appropriate waste storage in underground concrete lined repositories – potentially for hundreds of years. Ensuring the containers used can withstand the heat generated by their contents and monitoring the store for environmental releases of radioactive gases pose long term challenges for current measurement techniques. New waste handling facilities and measurement methods need to be developed to address nuclear site decommissioning requirements.

This project investigated methods and sampling regimes for in-situ radioactive contamination mapping, developed and characterised a waste segregation measurement system and devised new methods for assessing waste drum and large concrete structure integrity. It also developed systems for determining radioactive gas releases from high level nuclear waste storage facilities. This project builds upon the outcomes of Metrology for radioactive waste management.

The Project:

• Investigated methods for mapping radioactivity at nuclear facilities, including a newly developed gamma ray camera and a geostatistical modelling technique for depth-profiling contamination in building structures
• Developed a materials segregation facility for waste package characterisation for on-site installation, that is configurable for a range of radiation detection modes
• Developed radioactive gas monitoring systems for nuclear sites and radioactive waste repositories, for the detection of hazardous emissions containing tritium or carbon-14
• Developed waste package temperature-monitoring systems, to help identify container “hot spots” early and before thermally-induced damage can create the potential for radioactivity release.

This project has successfully developed methods for the safe and cost-effective decommissioning of nuclear facilities, ensuring waste materials are managed according to their identified hazards. A range of detection systems – for monitoring radioactive and thermal emissions – have also been assessed for nuclear sites and waste repository use. Both EDF and ANDRA are installing fibre optic distributed temperature sensing technologies to monitor the integrity of large concrete structures supported by a test facility commissioned during the project for evaluating the performance of electro-optical control instrumentation. The testing of prototype radiation detection instrumentation during the project has resulted in several companies developing commercial devices which are suitable for use at long-term high activity nuclear waste storage facilities.

In the long-term, project results will help provide measurement methods to enable the accurate consignment of decommissioning waste streams as nuclear sites are retired across Europe. The follow-on EMPIR project In-situ metrology for decommissioning nuclear facilities (MetroDECOM II) will continue EURAMET funded research in this area.