Deterministic Safety Technology for RBMK Reactors

Abstract

Recommended by Eugenijus UspurasThe present paper deals with the description of the technical activities conducted within the TACIS Project R2.03/97, 2 EC Contract no. 30303, related to RBMK. The project activities are focused toward the setting-up of a chain of computational tools suitable for the analysis of transients expected in the RBMK nuclear power plant (NPP). The accident leading to the rupture of one pressure channel, with fuel melting or high temperature damage, creep and brittle failure of the pressure tube and of graphite bricks with possibility of rupture propagation, constitutes the reference scenario for the project. However, a series of expected scenarios has been selected to prove the capability of the individual codes or chains of code in simulating the envisaged phenomenology. The paper summarizes the activities performed at NIKIET in Moscow and at University of Pisa (UNIPI) in Pisa. A top-down approach is pursued in structuring the executive summary that includes the following sections: (i) the safety needed for the RBMK NPP, (ii) the roadmap, (iii) the adopted computational tools, (iv) key findings, (v) Emphasis is given to the multiple pressure tube rupture (MPTR) issue and the individual channel monitoring (ICM) proposal.

Thermal-Hydraulic Analysis of Coolant Flow Decrease in Fuel Channels of Smolensk-3 RBMK during GDH Blockage Event

“…The MCC flow diagram of the RBMK is shown in the Figure 1 [4]. The main function of each pressure header (PH) is to collect the water that comes from the pressure pipes connected to all main pumps exit and supply the coolant to the twenty-two GDH through twenty-two pipes (325 × 15) mm.…”

“…At full blocking of GDH, the pressure in accidental GDH becomes approximately equal to pressure in SD. The reactor shutdown signal in case of coolant flow rate reduction, through FC of one GDH, will be generated only in emergency protection against low flow in GDH system [4]. In each of the about 40 GDH, some FCs are selected, distributed uniformly along the GDH, for flow rate measurement.…”

“…The RELAP5 nodalization of the Smolensk-3 developed by the UNIPI is divided into two parts identified as right and left sides [4]. The right side is more detailed and is considered as the damaged one.…”

“…Dollezhal Research and Development Institute of Power Engineering (NIKIET) and UNIPI. The document [4], confidential and restrict, deals with the description of the technical activities con-ducted within the technical assistance for the commonwealth of the independent states (TACIS) project. The activities were focused on the setting-up of a chain of computational tools suitable for the analysis of transients expected in the RBMK NPPs.…”

“…RELAP5 code has been used to perform the transient simulation. This code was originally designed for pressurized water reactors but has been successfully applied, as well as the RELAP5-3D version, for RBMK analyses [4][5][6][7][8].…”