Environmental behaviour and management of U-containing fuel debris particles

Lead Research Organisation: University of Bristol
Department Name: Interface Analysis Centre

Abstract

The proposed research will use U-containing particles found in the environment around the Fukushima Dai-ichi Power Plant as micro-scale representations of fuel debris and corium materials still inside the stricken reactors. By collecting, isolating and studying these particles we can build an improved knowledge base capable of underpinning the decommissioning of these highly degraded nuclear fuels within these damaged reactors (specifically Fukushima Daiichi, but also applicable to the Chernobyl nuclear power plant). There is equally an applicability to UK legacy nuclear sites, for example historic environmental contamination from Windscale or Dounreay. The development of this unique knowledge base will support a reduction in the hazard, cost and timescale of decommissioning, enabling accelerated decommissioning of nuclear sites. This may have a secondary impact of enhancing public acceptance of civil nuclear energy generation and geological disposal of radioactive wastes at an important time prior to the launch of the geological disposal facility siting process. At the same time, this research will build expertise towards the Civil Nuclear and Resilience Directorate's (CNRD) objectives to protect nuclear sites from threats and hazards; ensuring the UK's preparedness for civil nuclear emergencies and ensuring the UK is a leader on non-proliferation.

Planned Impact

The proposed research will support the UK Government's Nuclear Industry Strategy, by addressing the strategic aims to make demonstrable progress in the decommissioning of high hazard legacy waste and reactor decommissioning, to achieve a higher profile within international programmes on decommissioning and to establish collaborations overseas on nuclear decommissioning R&D and innovation.

Specifically, there are emerging concerns over the generation of radioactive aerosols during legacy waste retrievals and plant decommissioning. Through development of micro-sample harvesting and analysis techniques for high hazard nuclear materials, this UK-Japan collaborative research will provide underpinning evidence to support strategic and technical decision making in national and international nuclear decommissioning programmes, a key goal of the UK Nuclear Energy Research and Development Roadmap.

By appointing two early career researchers to perform this research (Martin and Corkhill), our project will further meet the goal of the roadmap to maintain the overall nuclear fission skills base. The research will have a long-term impact by developing the academic capability, facilities and basic technologies required to support decommissioning in the UK, Japan and international sites.

At the same time, we will contribute new techniques and subject matter experts to support the Civil Nuclear and Resilience Directorate's (CNRD) objectives to protect nuclear sites from threats and hazards and to ensure the UK's preparedness for civil nuclear emergencies. The work will also have the impact of helping to ensure the UK is a global leader on nuclear non-proliferation.

Our research will also have positive impact and value for the UK and Japanese public by increasing the transparency of the decommissioning occurring at the Fukushima site. By demonstrating that the academic experts supporting the decommissioning are both world-class problem-solvers and proactive in public engagement, we hope to positively impact public sentiments on nuclear power.
 
Description To date, this award has provided new insights into the conditions and mechanisms responsible for the 3 reactor explosions that occurred at the Fukushima Daiichi Nuclear Power Plant (FDNPP) following a magnitude 9 earthquake and damage to the reactors.

We have used advanced laboratory and synchrotron (x-ray laser) analysis techniques to look at the internal structure and chemical/elemental composition of nuclear fallout particles taken from the different plume zones, attributed to different reactor explosions. We have shown that for one of the three reactor units, there was a significant build-up in internal pressure within the reactor that was released by an explosion. This created fallout particles which had the micro-scale bubbly structure of pumice with tiny micron sized fragments of nuclear fuel (UO2). Fallout debris from the other reactor units did not have this structure, indicating that the explosions occurred at a time when there was no significant internal pressure build-up.

The study has also shown that:
1) The glass-wool insulation used to 'lag' the reactor was melted during the accident - meaning fallout particles contain lots of silica.
2) Analysis has shown that there are spent nuclear fuel particles in some of the fallout material (shown by direct observation and isotope profiling of Plutonium, Uranium and Cesium). These particles are angular, typical of fragmentation caused by an explosion.
3) We can differentiate between fallout materials derived from each of the 3 nuclear reactors that exploded.
4) We can understand the different pressure/temperature conditions existing in each reactor at the time of each separate explosion.
Exploitation Route The grant is still running to the end of September 2021 with COVID relief funding.
The IPAD database has started to promote sharing of data between the JAEA, Japanese university research groups and international collaborators.
Observations of fallout particles containing U and Pu is significant and will inform risk maps and rehabitation of the fallout zone local people.
Sectors Agriculture, Food and Drink,Communities and Social Services/Policy,Environment,Security and Diplomacy

 
Title International Particle Analysis Database - IPAD 
Description With funding from the University of Bristol Cabot Institute and STFC IPS capital funding we have established jointly with the JAEA, Japan a particle analysis database for nuclear forensic 'hot' particles. This database is also sanctioned and sponsored by the IAEA. Launched in 2020, this database will be the repository for shared nuclear forensic data from fallout analysis - primarily for Fukushima but also for other 'incident' or 'interest' sites around the world. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact It is too early to define the impact. Expected impact is that this database will become a reference and tool for nuclear forensics specialists around the world and provide a neutral portal for sharing data. 
 
Description JAEA Fukushima fallout collaboration 
Organisation Japan Atomic Energy Agency (JAEA)
Country Japan 
Sector Public 
PI Contribution The two teams (Bristol and JAEA) have formed a collaboration to research aspects of the fallout material ejected from the Fukushima reactor explosions in March 2011. Specifically, Bristol have applied advanced materials analysis techniques to samples of fallout material to determine its physical size, structure, morphology, elemental composition and isotopic signature. This complements the analytical capability and activities at the JAEA CLADS facility in Tomioka. Bristol has also gained STFC funding and established a secure database for the collection, sharing and analysis of data relating to fallout materials collected from different regions of the Fukushima fallout zone. JAEA had substantial input into the design and access arrangements for the database and associated wed interface.
Collaborator Contribution The JAEA side have provided analysis, by electron microscopy, gamma spectrometry, SIMS and autoradiography to determine the size, number, activity and isotopic characteristics of fallout materials to complement the Bristol data. They have also collected other particle/fallout analysis data from other research groups in Japan to add to the database.
Impact This is a multi-disciplinary collaboration centred around materials analysis and radiation mapping. The work has led to numerous publications and a joint collaboration agreement between JAEA and Bristol, which is renewed on a 3 yearly basis.
Start Year 2017
 
Description Japan Atomic Energy Agency 
Organisation Japan Atomic Energy Agency (JAEA)
Country Japan 
Sector Public 
PI Contribution The grant award has led to the establishment of a strategic partnership with the JAEA based around fallout and fuel debris analysis. There has been an MoU signed by both institutions to permit collaboration, exchange of personnel and samples. Subsequently, the remit of the MoU has been widened (2019) to include joint work on diamond battery (ASPIRE) technology, high dose-rate diamond detectors and radiation mapping robots. We have contributed expertise, consultancy, shared data recorded from Japanese samples and sites and have won several experimental sessions at the Diamond Light Source synchrotron facility for fallout particle analysis. JAEA colleagues have participated in all of our UK synchrotron experiments and participated and presented at UK workshops and conferences e.g.
Collaborator Contribution Already we have had over 15 visits from the JAEA since the start of the partnership as well as a suite of fallout samples from Fukushima and access to nuclear fallout storage sites and other restricted areas of the Fukushima fallout zone. The site access and samples provided are extremely valuable.
Impact Several joint publications. Widening of the relationship to cover other areas such as radiation detection, UAVs and most recently diamond batteries.
Start Year 2016
 
Description University of Kyoto - Fukushima collaboration 
Organisation University of Kyoto
Country Japan 
Sector Academic/University 
PI Contribution The two teams (Bristol and Kyoto) have formed a collaboration to research aspects of the fallout material ejected from the Fukushima reactor explosions in March 2011. Specifically, Bristol have applied advanced materials analysis techniques to samples of fallout material to determine its physical size, structure, morphology, elemental composition and isotopic signature. Bristol has also gained STFC funding and established a secure database for the collection, sharing and analysis of data relating to fallout materials collected from different regions of the Fukushima fallout zone
Collaborator Contribution The Kyoto side have provided analysis, by electron microscopy, gamma spectrometry and laser techniques to determine the size, activity and fluorescence characteristics of fallout materials to complement the Bristol data. They have also collected other particle/fallout analysis data from other research groups in Japan to add to the database.
Impact This collaboration is multi-disciplinary but mainly focused around materials analysis and radiation mapping. The collaboration has led to joint UK-Japan nuclear research projects funded by EPSRC and MEXT. It has also led to STFC funding to form a collaborative 'nuclear particle forensics' database. This partnership has also led to the development of a partnership between Bristol and the Japan Atomic Energy Agency (JAEA).
Start Year 2013
 
Title IPAD database 
Description The International Particle Analysis Database (IPAD) is an user access database designed for the storage, sharing and analysis of materials analysis data from fallout materials collected (and analysed) from different areas of the Fukushima fallout zone. The database data (stored on AWS) can be interrogated via the IPAD web interface and data patterns can be derived using different data plotting filters. 
Type Of Technology Webtool/Application 
Year Produced 2020 
Impact This product allows for different research groups to share and collectively pool their data sets to determine trends that are only visible when many data are compiled for analysis. 
URL https://www.youtube.com/watch?v=kLbBWEL6L5w
 
Description Diamond Light Source Annual Review 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The Diamond Light Source annual review contains an article about the work on the UK-MEXT project on Fukushima fallout analysis using advanced synchrotron analysis techniques to determine the conditions and mechanisms for the different reactor explosions at FDNPP.
Year(s) Of Engagement Activity 2020