В Work on the creation of the complex of cryogenic moderators is underway in the Laboratory of Neutron Physics. The moderators will surround the hexagon of the IBR-2 reactor core on three sides. The project is completed, these moderators will form an individual spectrum of the neutron beam at 11 and 14 experimental channels of the reactor. The complex is a set of three moderators similar in terms of operation principles but with different forms and the layout of head parts each of which is being developed individually depending on experimental facilities and research methods for which they are created.

In 2012, the cryogenic moderator of the first stage CM 202 was installed. Nowadays, this moderator has run more than 4,000 hours at the IBR-2 capacity, including 1,500 with the new cryogenic system based on the Linde AG Kryotechnik refrigerator with a capacity of 1,200 under 10 K and the KGU 700/15 refrigerator of the NPO “Geliymash” JSC. During the operation of the setup, a series of studies at extracted beams of the reactor was carried out, neutron physical characteristics of the moderator were studied, the operation of engineering systems and software was analyzed.

Test for tightness conducted by FLNP staff members V. A. Skuratov, D. V. Zaitsev and specialists of NPO “Atom” JSC V. I. Zagulov and A. V. Anisovets

At the same time, the production of the second-stage moderator of the CM 201 complex continued. This moderator occupies a so-called central direction and forms the neutron beam spectrum for experimental beams No. 1, 4, 5, 6, 9. In 2018, this moderator was produced for the NPO “Atom” JSC and provided for fitting on-site (near the reactor zone), filling the biological protection unit with a special concrete composition and checking of chambers and pipelines of the moderator for density and tightness.

It should be noted that not only the moderator itself, its loading principle and the form of the working substances are unique but also the entire infrastructure (the cryogenic cooling system, thermometry equipment, flow control system, ball movement control, software for the process visualization and control, etc.) Specialists providing trouble-free and uninterrupted operation of the moderator complex and their engineering systems are also unique. It is noteworthy that the team implementing the project is engaged also into the development of the moderator system and the development, adjustment and introduction of new nods and complex control systems. One of the brightest examples of such developments is the method of registration of ball movement when loading the moderator.

Nowadays, work on commissioning the cryogenic neutron moderators is underway, and the CM 201 moderator will provide experimentalists with its first cold neutrons in November 2020 according to the IBR-2 reactor schedule.

The authors of the article express gratitude to main participants of the project, namely the teams of Group No. 2 of the Mechanical and Technological Department, DSC Group No. 6, they are also grateful for constructive consultations and comments by A. A. Bednyakov, A. V. Dolgikh, S. A. Kulikov, E. P. Shabalin, NIKIET staff members, the FLNP Directorate. The team will always remember V. D. Ananiev, A. A. Lubimtsev, A. P. Sirotin who have passed away, whose participation in the project, experience and knowledge were invaluable.

A. V. Galushko, V. A. Skuratov, N. O. Volnukhin, A. Yskakov, I. V. Zhidkov, N. A. Burov, K. A. Mukhin commission the nod for ball counting

Konstantin Mukhin, Leader of the CM project,
Maksim Bulavin, Head of DSC Group No.6,
photos provided by FLNP