Slug Impact Loading on the Vessel Head during a Postulated In-Vessel Steam Explosion in Pressurized Water Reactors–Assessments and Discussion of the Investigation Strategy

The Risks of Nuclear Energy Technology

“…Figure 2.10 shows the criticality or effective multiplication factor, k eff , as a function of the volume ratio of the moderator (Light Water Reactor) to fuel in a lattice cell (Fig. 2.5) in a LWR core [37]. This volume ratio of moderator to fuel varies if the moderator density or the distance, p, between the fuel rods with diameter, d, of the lattice cell changes.…”

“…2.10 the lattice cell is called undermoderated with lower pitch to fuel rod diameter, p/d, ratio. It is called overmoderated in the range right of the maximum of the curves (higher p/d ratio) [23,36,37].…”

“…On the basis of an impulse model by Riera [36,37], and after evaluation of penetration and shock experiments with bullets fired at steel-reinforced concrete walls, the shock load-vs.-time curve shown in Fig. 7.7 was defined and laid down around 1977 for new nuclear power plants to be built [10].…”

“…7.7 was based on computer models by Riera [36,37] and Drittler [32][33][34]. In 1980, Riera showed a comparison of these models and findings.…”

“…6 h, 0.3 % after 1 week, 0.1 % after 3 months and 0.04 % after 1 year and 0.006 % after 3 years for a burnup of 50 MWd/kg. This decay heat power is slightly dependent on burnup and increases somewhat with higher burnup for cooling time periods up to about 100 years [1][2][3][37][38].…”