Fuel management at the Kyiv research nuclear reactor VVR-M of the National Academy of Sciences of Ukraine

Fresh Fuel Management

Storage facility for fresh fuel of VVR-M research reactor refers to class 2 storage facility, which provides the following:

  • exclude storage facility flooding by water;
  • locate storage facility above zero level;
  • no pipes with water, oil and hydrogen in storage facility;
  • availability of water detectors and drainage system in storage facility.

Fuel assemblies (FA) are stored in storage facility in factory package, i.e. transport packaging complex ТK-S14. Packaging complex (cask) is certified for transportation of fresh FA of VVR-M type. FAs are strongly fastened in cask and do not move during transport by any vehicle.

Racks and casks with FA are strongly fastened to disable their arbitrary movement.

The storage facility is equipped with the physical protection system, which complies with the requirements of the Convention on the Physical Protection of Nuclear Material, and systems (equipment) for safe storage of nuclear fuel:

  • alarm system to detect initiation of self-sustained chain fission reaction;
  • radiation monitoring system;
  • water detection and monitoring system;
  • drainage system;
  • fire alarm system;
  • primary firefighting means;
  • means for lighting, and reliable power supply;
  • ventilation system.

Temperature and humidity are also monitored in the storage facility.

Spent Fuel Management

The spent fuel storage system of VVR-M produced by Kyiv Institute for Nuclear Research of the NASU includes two spent fuel pools for SNF, namely BV-1 and BV-2, and devices with equipment for reloading.

Spent fuel pool for spent fuel assemblies BV-1. Brief description.

BV-1 spent fuel pool was constructed and put into operation in 1960 for safe unloading of spent fuel assemblies from the core.

Spent fuel assemblies are transported from under reactor tank cover to spent fuel pool BV-1 through declined channel located inside the reactor biological protection.

Storage unit of spent fuel assemblies has two levels: level 1 is a design level and level 2 was additionally constructed.

BV-1 spent fuel pool is filled with demineralized water, which provides biological protection and heat removal from fuel assemblies by convection. Spent fuel pool perimeter is surrounded by a heavy concrete with thickness of 1.26 m.

Required quality of water in the spent fuel pool is maintained by movable ion-exchange filter.

The transport system for spent fuel assemblies from the core to spent fuel pool BV-1 and back provides simultaneous transport of only one fuel assembly.

Modernization of the management system for VVR-M spent nuclear fuel.

Kyiv Institute for Nuclear Research of the NASU modernized SNF management systems for reactor operation safety improvement, this provided new components: pool for SNF temporary storage (BV-2), SFA transport system from BV-1 to BV-2 and back, transport by bridge crane with loading capacity of 15 t, remote control means for SFA (bars, electronic light, small video cameras, optical device), mobile filter unit for water purification in spent fuel pool.

The main component of the modernized system is additional spent fuel pool for spent fuel assemblies (BV-2). Its main parts are reinforced concrete box, pool tank with operating camera, SFA storage unit, upper biological protection (metal folding lid), distillate filling system, special ventilation system, parameter monitoring system (water level and temperature, rarefication in space above water table), radiation monitoring system, and monitoring system of possible initiation of self-sustained chain fission reaction.

SNF storage unit includes four individual sections of aluminum alloy sheets АМ-4 with thickness of 20 mm. These sheets have openings for location of SFA and neutron absorber rods. Movement of SFA and absorbers inside a cell is impossible due to grid structure, which fastens them reliably. Absorbers are stationary and may not be incidentally removed.

BV-2 is located in a room, which is adjacent to the reactor hall.

VPVR/M cask used in the research reactor is designed and manufactured individually for transport and storage of spent FA produced in the Russian Federation. The designer (SKODA, the Czech Republic) certified the cask.

SNF management system life is 20 years.

Fuel transport, refueling and storage system in DR-100 research reactor of Sevastopil National University of Nuclear Energy and Industry

Fresh fuel storage facility

Fresh fuel storage facility in DR-100 research reactor and storage facility of Kyiv Institute for Nuclear Research at the NASU refer to class 2 storage facilities.

This storage facility is a reinforced concrete box resistant to earthquake (up to magnitude 7 earthquake) and falling of structural components from DR-100 building that does not include the materials, which are efficient neutron moderators.

Fresh fuel is stored in the storage facility in form of fuel elements (FE) and fuel assemblies (FA) in special thermal protective boxes (4 boxes strongly fastened on the floor of storage facility). Fuel elements are stored in transport packages, and fuel assemblies are stored individually and installed in special cells.

Spent (irradiated) fuel storage facility (storage well)

Irradiated (spent) fuel is stored in special wet-type pool (storage well) located in biological protection array of DR-100 research reactor.

Storage facility diameter is 1200 mm.

Storage facility height is 4500 mm.

Volume of poured water is 4 m3.

Operating level of distilled water in storage facility is 4020 mm.

The following is accepted in storage well as biological protection:

  • upwards – distilled water;
  • radially – concrete;
  • during loading, unloading and transport of FA – protective cask.

FAs are unloaded from reactor tank to storage well and back one by one in a protective cask. This cask is loaded and unloaded by special can with FA installed in it. The can is fastened by rope and moved by hoist on the cask. FA is transferred in the storage well manually by bar with collet fixture.

Storage well case is welded cylindrical vessel made of aluminum alloy marked AD1 with internal diameter of 1200 mm and height of 4270 mm.

The grid for FA installation is made of two sheets connected with each other by pipes, which are welded into sheet openings. During storage facility loading, FA bottom nozzle is inserted into grid pipe, this provides fuel assembly spacing during storage and excludes its movement.

Resulting from the calculations, Kø (effective neutron multiplication factor) does not exceed 0.423 +/- 0.007 for infinite number of FAs in DR-100, which are located in water with stroke of 100 mm in triangular grid.

Accounting and monitoring of location, number and transfer of FEs and FAs is provided at all stages of nuclear fuel management.

References:

  1. SNRIU Material