(230g) Postulation for a Novel Passive System for Post-Accident Reactor Containment Cooling

Postulation for a novel
passive system for post-accident reactor containment cooling

Natural circulation is the most
important and attractive heat removal mechanism for passive safety systems due
to high reliability in the new design of nuclear power plants. It is required
to investigate the flow and heat removal capability of loops to design the
natural circulation loops (NCLs) so that it can be used efficiently as a
passive heat removal system in a nuclear reactor. Natural circulation is postulated
to be useful for removal of heat from containment shell during accidents or
after the accidents. During the nuclear accident, the steam generation rate is
high that lead to increase the pressure of containment. Further, dissociation of
steam produced hydrogen that is explosive in nature. In the last few decades,
extensive research is done on NCLs having horizontal heating by constant heat
flux source, and horizontal cooling by the water-cooled heat exchanger. An
incompressible one-dimensional (1-D) analytical model is proposed to
investigate the rate of steam condensation capacity of NCLs in the nuclear
containment in case of hypothetical design basis accidents like loss of coolant
accident (LOCA) or Main steam line break (MSLB). The typical configuration of proposed rectangular loop is
shown in Fig.1.

Fig. 1. The
typical configuration of proposed rectangular loop.

Steam generated within the
containment following design basis accidents is condensed with the lower arm of
the loop. Therefore, pressure rise within the containment is also prevented
which helps to prevention of nuclear containment explosion. During initial
phase of post-accident, passive spray of water into containment environment to
condense the steam is required to reduce the pressure within containment and to
reduce the temperature. Later on, the proposed passive containment cooling
system (PCCS) can be used for cooling the containment on long term. The steam
condensation capability of the proposed PCCS for different geometrical
parameters i.e., vertical height and hydraulic diameter of the tube is
presented. Hydrogen forms from dissociation of steam following the design basis
accidents. If concentration of hydrogen crosses the low explosive limit (LEL),
then there is a chance of containment explosion. Therefore, prevention of
formation of hydrogen by condensing the steam is very useful technique to avoid
nuclear accident by containment explosion. In this regard, the numerical
analysis is very useful for theoretical design of NCLs for removal of heat
from the containment in post-accident condition. Details will be
provided in the full paper.