Feasibility symposium on converting BNC into a CANS facility

Sat, 07/10/2021

A mini-symposium was held in BNC on 8 July 2021 entitled “Conversion of the Budapest Research Reactor into an accelerator-based neutron source” discussing the future of neutron science in Hungary following the life-cycle of the Budapest Research Reactor around 2027-30. With the advent of the accelerator-based compact neutron source (CANS) technology a possible option is - rather than full decommissoning - to convert the nuclear facility into a CANS site. As the conversion is an immense, novel and complex project, effecting the various neutron techniques differently, a well thought out decision is required in due time. The mini-symposium was the first step on a long road.


István Vidovszky  Alex Szakál Márton Markó
Feasibility study of the accelerator-based neutron source Accelerator-based neutron source technology BNC instrumentation – following the transition to a CANS
Round-table discussion

The discussion was attended by the directors of the Research Institute of Atomic Energy and of the Institute for Energy Security and Environmental Safety, as well as by the senior staff of the Nuclear Analysis and Radiography, the Neutron Spectroscopy, the Environmental Physics and of the Reactor Operation Department. Following the presentations, a discussion took place on the presently foreseen technical solutions and on the administrative issues that may arise during the reconstruction.

The symposium was organized in the framework of a ‘migration study’ project launched by management of the Centre for Energy Research in 2020. The Budapest Research Reactor (BRR) produces neutrons using a (20% enriched U-235) material by nuclear fission, which is becoming increasingly difficult to maintain from safety-regulation and financial points of view. The nuclear fuel costs are steeply rising and the safety requirements are becoming increasingly stringent. Alternatively, compact neutron sources (CANSs) are becoming possible to use to replace medium-power reactor sources for materials research. In such a facility, neutrons are produced in a nuclear reaction of a medium-energy (2-80 MeV) proton or electron beam with e.g. a Li or Be target, without the presence of fissile materials. This type of („stripping”) nuclear reaction has long been known, but its use in a neutron source has only been made possible recently by three important developments: i) the accelerator technology has become relatively inexpensive and commercially available, ii) much increased neutron yields, due to complex moderator / target developments. iii) neutron optical simulations, as well as implementations of neutron optical components resulting in an order of magnitude increase in the number of neutrons detectable in the experiments. The ESS solution (by L. Zanini, F. Mezei et. al.,) of this problem may serve as a guide in converting a research reactors into CANSs. A test neutron source which is being built at Martonvásár, Hungary, with the participation of the Centre for Energy Research, can be considered a prototype of the CANS device to replace BRR, and the experience being accumulated in the design of the trest machine can be used directly.

The first presentation by dr. István Vidovszky analyzed the BRR decommissioning process, reviewing the status of the nuclear facility, and examined the conversion of the reactor into a large-scale CANS-type plant as a “brownfield” investment.

In the second presentation dr. Alex Szakál gave an overview of the CANS facilities already operating or planned all over the world, primarily with regard to the technologies that may be feasible to implement in Budapest.

The third presentation by dr. Márton Markó outlined the instrumentation issues, on the one hand from the point of view of a pulsed neutron source, like CANS, and on the other hand from the point of view of the instrument suite of BNC's existing equipment, with emphasis on the competence and interest of BNC’s researchers.

During the round table discussion, the following major questions arose and suggestions were made:

  1. Partial decommissioning of the Budapest Research Reactor is feasible. The main conditions required for the detailed elaboration of the decommissioning plan are: an essential specification of the CANS to be placed in the reactor site and timely detailed consultation with the licensing authority. Recommendation: Prepare a preliminary study on the complex concept of the accelerator-target moderator (deadline: 30 June, 2022), then prepare a detailed decommissioning plan.
  2. The prerequisites for obtaining an exemption from nuclear safeguards are the following: removal of nuclear fuel from the BNC site; signing a Russian-Hungarian interstate agreement on the removal of fuel elements. Safe placement of beryllium on the BNC site. Recommendation: Make the Ministry of Industry and Technology to initiate contact with the Russian partner for a future Russian-Hungarian agreement on the subject.
  3. In connection with the second presentation, it is recommended to create a working group that examines the possible configurations of the CANS to be installed in BNC, such as the main parameters of the accelerator, the number and specification of the targets and moderators. Evaluation of the BRR infrastructure for an optimum accommodation of the CANS. (Link to point (a))
  4. Instrumentation recommendations: as a continuation of the ‘migration study’, current scientific and technical needs should be examined without delay. So on the one hand, the equipment of the future CANS has to be designed according to the ‘scientific case’. On the other hand, BNC's existing equipment suite and the competence of BNC’s researchers must be the guideline in rescuing or abandoning equipment, in the process of establishing new ones.
  5. There was a general consensus among the participants that it was advisable to keep the current building infrastructure as much as possible – but considering additions to e.g. provide placement of longer (~ 40 m) neutron guides. Certainly, setting up the new equipment together will require a full redesign of the ‘lay-out’ and the beam transport.
  6. It is expedient to set up an instrumentation working group (led by Márton Markó) to develop an ‘initial suite of instruments’ proposal. Recommendation: taking into account points d-e), a concept consisting of 6-8 devices should be prepared (indicating the priorities), as a starting point for the development of the CANS specification on the one hand, and a discussion and guide of development of detailed plans on the other.
  7. As an indication, it is expedient to outline further 4-6 devices, which may serve to attract international investor interest. It was agreed that the equipment design also significantly exceeds the current BNC research capacity. Additional resources must be created for the equipment design task. In the meantime Hungarian researchers working in research facilities abroad and occasional involvement of foreign colleagues closely associated with BNC is recommended. Recommendation: An Instrumentation Workshop to organize in the spring of 2022.
  8. During the discussion, significant emphasis was placed on timing and organization. Péter Juhász drew attention to the vital importance of consulting with the licensing authority and extending the operation permit presently valid until 2023. The essential considerations are: scheduling the use of the fuel assembly; e.g. if the stock is expected to be depleted in 2027, a decision on financing is required in 2025 at the latest, according to the following options:
    • purchase of additional fuel and continuation of the rector's operation;
    • final shutdown of the reactor and complete decommissioning
    • transition to an accelerator-based neuron source

The 2025 financial decision requires at least two years of preparation, and it is advisable to start preparatory work immediately after having obtained the extended permit in 2023. This implies that the ‘migration study’ project will have to present the scientific and technical plans in detail by the end of 2023.

Finally, the issue of financing the ‘transition’ has been raised, which is certainly only possible with government support. A preliminary economic-financial analysis was suggested by the attendees to be carried out as soon as possible, covering the major cost items of ‘conversion’, such as partial decommissioning of the reactor; fuel cycle; conversion of building infrastructure and CANS investment costs; including instrumentation. Cost alternatives (purchase of additional fuel or complete decommissioning) should also be considered, in particular given that CANS and the reactor mode can serve different types of research and economic activities. This analysis is due in the second half of 2022 and can be largely addressed as an internal project of the Centre for Energy Research. However, the 2025 financial decision will require a deeper assessment of socio-economic impact, therefore the timely involvement of an expert financial advisory firm is recommended.

A systematic implementation of the National Neutron Research Roadmap and the BRR modernization program, is of paramount importance in the BNC staff’s activities concerning the future of the research reactor. Quality work is the precondition of high-level international research and of profitable economic activity. A reliable operation of the reactor over the next 6-7 years and spectacular experiments on some excellent equipment will ensure domestic neutron research to be maintained on a long run at a high standard. BNC’s achievements in the next few years will play a crucial role in the decisions of government financing.

As a current rough estimate, HUF 40 billion is necessary for the foreseen megaproject of the CANS transition by the end of the decade, thus the preparation of fundraising is becoming an urgent task. This activity should be included in the current (2021-24) modernization of BNC, a project estimated to require approx. HUF 8 billion.