The PSB RBMK test facilityis a large scale integrated installation, simulating one loop of the forced recirculation circuit (FRC) of RBMK–1000 reactor. The volume and power scaling factor for the reactor loop is 1:140, volume and power scaling factor for a fuel channel — 1:1, elevations of component are consistent with those for the prototype reactor.
       The test facility consists of six full-scale models of the fuel channels of RBMK reactor (one high power channel — 3–4 MW, two medium power channels — 2 MW, and three low power channels — 1 MW), drum steam separator model, models of suction, pressure, and group distribution headers, models of valves and elements of armature of FRC. Models of the test facility fuel channels simulate axial removal of coolant flow after its passing through the core as it is in the actual RBMK reactor channel. The drum separator model is designed for the conditions of the inventory per fuel channel identical to RBMK, and with preserved elevations of the components within the reactor cavity and nozzles relative to each other. The geometric dimensions of the headers and pipelines of the test facility are defined from the requirement of preservation of the assumed volume and power scaling factor of the PSB RMBK and the condition of the coolant transport time in the FRC and its component being equal to that in the RBMK reactor.
       The PSB RBMK test facility also includes simulators of the major reactor systems – emergency core cooling system (ECCS), feedwater system and emergency protection system. The ECCS model contains all the major ECCS components of RBMK reactor. For accurate simulation of the emergency cooling process, there are models of the short term ECCS (accumulator tanks) with injection of the cooling water from pressurized accumulator tanks, and long term ECCS (injection of cooling water into ECCS header from the ECCS pumps). For investigation of LOCA, the PSB-RBMK test facility allows for connecting the leak-of pipes to the simulated FRC break locations.

Purpose of the PSB RBMK test facility and main lines of experimental studies

       The PSB RBMK test facility is designed for experimental studies of thermo-hydraulic processes occurring in the FRC of the RBMK reactor in maintenance, transient and accident modes. The results of the experimental studies can be directly applied for the reactor operation mode analysis, used for validation of effectiveness of the suggested accident prevention measures and for validation of the thermo-hydraulic codes. The PSB RBMK test facility can be used for testing and refinement of new components and structural elements of the FRC under the conditions, maximally close to those of the prototype reactor. The experimental data can also be used for determination or correction of the correlations for hydraulic resistances, critical heat flows, beyond departure of nucleate boiling heat transfer, as well as for investigation of thermo-hydraulic oscillations (instability) in the adjacent channels.

Results

       In 2004, concern «Rosenergoatom» approved the «Programme of Tests at PSB-RBMK Test Facility for Validation of Thermo-hydraulic Code RELAP5 as applied to RBMK Reactor». The objective of the «Programme of Tests…» is to execute integral experiments on a study of thermo-hydraulic processes in the RBMK recirculation loop under accident and transient conditions. As a result of the experiments it’s expected to obtain currently lacking database for valuable validation of thermo-hydraulic codes (first of all RELAP5) as applied to RBMK reactor.
       In the period of 2006 - 2008 the experiments of investigation of the following accidents of the RBMK-1000 were carried out on the PSB RBMK test facility:

• Lowering of flow rate in one distributing group header (DGH) because of damage of the mechanical filter at the entrance to the DGH;
  • Cooling of the reactor core in the mode of natural circulation when there is an electrical supply fault of NPP’s own needs;
  •  A brake of the steam pipeline outside compartments of the System of Accidents Localization with an electrical supply fault of the power unit;
  • A brake of the downflow pipeline;
  • Full double-ended break of the pressure header.

         Experimental investigations were supplemented with verification calculations using the code RELAP5/MOD3.2.
         The work was done within the framework of TACIS R2.03/02 project and of the contract with Concern «Energoatom».
         
  
  

  The investigation of the RBMK-1000 accident «Full bilateral break of the pressure collector»

  Separate pressure. Comparing of the calculation results p_40010000 with the experimentation YA10P01a.

  Temperatures of the casing of the fuel channel simulate in different points along the experimental channel’ altitude. Comparing of the calculations’ results (httemp 131100204, httemp 131102004) with the experimentation (YA21T32a , YA21T45a).