Although Russia has successfully converted many foreign research re­actors from HEU fuel to LEU fuel, it has not historically had a domestic conversion program comparable to that of the United States. To date, no research reactors in the Russian Federation have been converted from HEU to LEU fuel. However, as noted in Chapter 1, in December 2010 the U. S. and Russian governments agreed to initiate feasibility studies to analyze the conversion potential of the following six Russian research reactors that are currently operating with HEU fuel:[72]

1. MIR. M1 (Research Institute of Atomic Reactors [RIAR], Dimitrovgrad);

2. IR-8 (Kurchatov Institute, Moscow);

3. OR (listed as OP-M in Table 1-2 in Chapter 1) (Kurchatov Insti­tute, Moscow);

4. ARGUS (Kurchatov Institute, Moscow);

5. IRT (Moscow Engineering Physics Institute [MEPhI], Moscow);

and

6. IRT-T (Tomsk Polytechnical Institute, Tomsk).

The feasibility studies for these reactors are planned to be completed at the end of 2011.

During the symposium, significant concern was expressed by many members of the Russian delegation regarding the possibility of performance degradation accompanying conversion from HEU to LEU cores. Many members of the U. S. delegation were significantly more optimistic that good design of the replacement LEU core could eliminate concerns about performance degradation. This difference in view may be attributable to the considerably greater U. S. experience with research reactor conversions (see Chapter 2).

The current missions and currently assessed conversion potentials of five of the six reactors listed above were described by Russian presenters during the symposium:

• V. A. Starkov (RIAR) discussed the conversion potential of MIR. M1 (Starkov, 2011).

• V. A. Pavshuk (Kurchatov Institute) discussed the conversion poten­tial of Argus (Pavshuk, 2011).

• V. A. Nasonov (Kurchatov Institute) discussed the conversion po­tential of IR-8 (Nasonov, 2011).

• Yu. A. Tzibulnikov (Tomsk Polytechnic Institute) discussed the con­version potential of IRT-T (Tzibulnikov, 2011).

• E. A. Kryuchkov (MEPhI) discussed the conversion potential of IRT (Kryuchkov, 2011).

Because the feasibility studies of these reactors were at an earlier stage of development than the U. S. studies when the symposium was held, less detail is provided in presentation summaries than was given for the U. S. reactor conversions.

MIR. M1

V. A. Starkov

The MIR. M1 reactor is a 100 MW pool-type research reactor located at RIAR in Dimitrovgrad. It has a maximum thermal neutron flux at the experimental positions of 5 x 1014 n/cm2-s. Its primary mission is to test experimental fuel assemblies and fuel rods under normal, abnormal, and accident conditions.

The core and beryllium reflector blocks are stacked in a hexagonal grid comprising 127 hexagonal blocks 148.5 mm in size, installed at a pitch of 150 mm (see Figure 3-7). Four central rows of beryllium blocks operate as

• • Conirol and safety rod

:Qi Combined hanger consisting of the operating fuel assembly and absorber

a moderator, and two external rows of beryllium blocks act as a neutron reflector. The core also contains 11 loop channels where experiments are placed. Each experimental channel is surrounded by six fuel assemblies to maximally isolate each experiment from neighboring experiments. Each fuel assembly consists of four cylindrical fuel tubes arranged concentrically (see Figure 3-8). Absorbing rods are located along the edges of the blocks. For every channel there are two to three such absorbers for a total of about 30. This core design is very flexible and allows for the simultaneous irradia­tion of multiple experiments in different power regimes.