Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Design approach to local blockages

Roychowdhury, D.G.; Govindarajan, S.; Chetal, S.C.; Bhoje, S.B. (Indira Ghandi Centre for Atomic Research, Kalpakkam (India))

Abstract

In LMFBR, whole core meltdown accident falls in residual risk category. Propagation of a localfault to whole core, however, needs attention. Subassembly accidents are divided into two categories, Design Basis and Beyond Design Basis accidents. Design Basis is further classified into four categories. All events affecting fuel pin performance are identified and categorised. Total Instantaneous Blockage has been identified as the envelope of all local faults and categorised as BDB event and the safety objective is to demonstrate that no damage will propagate beyond six neighbouring SA. A core catcher has been provided for retention of core debris and cooling it by natural convection. Local blockages may be active and passive. Active blockages can be detected by DND signal. For passive blockages, detection is difficult. Hence, development of a finite volume computer code based on the porous body formulation has been undertaken to define the maximum allowable defect. Experimental programmes have been undertaken to understand blockage mechanism, define maximum credible defect and the thermal-hydraulic behaviour of SA with local blockages. Also an experimentaI programme with a totally blocked SA with a bundle of heated pins has been undertaken to understand the behaviour of the SA.

view the full text of this article (12 pages, format: PDF, size= 673kB)

key words: defects; design basis accidents; experiment planning; flow blockage; fuel pins; hydrodynamics; lmfbr type reactors; maximum credible accident; meltdown; risk assessment; thermal analysis
Reference:
Technical committee meeting on methods and codes for calculations of thermohydraulic parameters for fuel, absorber pins and assemblies of LMFR's with traditional and burner cores. Obninsk (Russian Federation) 27-31 Jul 1998
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1157, pp:284-295