An Advanced Design Concept of a Direct Vessel Injection
- KAERI 150 Duckjin-Dong, Yuseong-Ku, Daejeon (Korea, Republic of)
The ECC direct bypass fraction during a late reflood phase of a LBLOCA is strongly dependent on the cross flow in the downcomer of a pressurized light water reactor. An ECC flow channel, which is separated or isolated from such a high-speed cross flow, is a considerable design feature to mitigate the ECC bypass fraction. The dual core barrel cylinder is located between the reactor vessel and the core barrel outer wall in the downcomer annulus. The new narrow gap between the core barrel and the additional dual core barrel plays a role of a downward ECC flow channel. The flow zone around a broken cold leg in the downcomer has the role of a high ECC direct bypass due to strong suction force while the wake zone of a hot leg has the role of an ECC penetration. Thus, the relative azimuthal angle of the DVI nozzle from the broken cold leg is a considerable parameter. The azimuthal angle reallocation to shift the DVI nozzle from a cold leg to a hot leg is a considerable design concept to avoid a high suction flow zone when the ECC water is injected. The other enhancing mechanism of an ECC penetration is a grooved core barrel which has small rectangular-shaped grooves vertically arranged on the core barrel wall of the reactor vessel downcomer. These grooves have the role of a generation of a vortex induced by a high-speed lateral flow. Since the vortex is stagnant and rotational, the pulling force of an ECC drop or film to flow out through a broken cold leg is minimized. The open channel of grooves generates a stagnant vortex, while the closed channel of grooves creates an isolated ECC downward flow channel from the high-speed lateral flow. The grooved channels allow the ECC flow downward to the lower downcomer due to gravity. This causes a reduced direct ECC bypass fraction. In this study, new design concepts of a dual core barrel cylinder, grooved core barrel, and a reallocation of the DVI azimuthal angle are proposed and tested by using an air-water 1/5 scaled air-water test facility. The ECC direct bypass reduction performances of the new design concepts have been compared with that of the standard type of DVI injection. The azimuthal angle of the DVI nozzle from the broken cold leg varies from -15 degrees to +52 degrees toward the hot leg. The test results show that the azimuthal injection angle is an effective parameter to reduce the direct ECC bypass. The elevation of the injection nozzles is also an important parameter to reduce the direct bypass. The most effective method for reducing the direct ECC bypass is a dual core barrel. The reduction fraction when compared to the standard DVI is about -30% for the dual core barrel while it is -15% for the grooved core barrel. (authors)
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 21016424
- Resource Relation:
- Conference: 2006 International congress on advances in nuclear power plants - ICAPP'06, Reno - Nevada (United States), 4-8 Jun 2006; Other Information: Country of input: France; 7 refs; Related Information: In: Proceedings of the 2006 international congress on advances in nuclear power plants - ICAPP'06, 2734 pages.
- Country of Publication:
- United States
- Language:
- English
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