Page 201 - Managing Global Warming

Current and future nuclear power reactors and plants 163

the neutron spectrum in case of core voiding. A preconceptual design of safety
systems for both options has been studied with transient analyses.
A preconceptual plant design with 1700-MW-net electrical power based on a
pressure-vessel-type reactor has been studied by Yamada et al. [15] and has been
assessed with respect to efficiency, safety, and cost. The study confirms the target
net efficiency of 44% and estimates a cost reduction potential of 30% compared with
current PWRs. Safety features are expected to be similar to ABWRs.
A preconceptual design of a pressure-vessel-type reactor with a 500°C core outlet
temperature and 1000-MW electrical power has been developed in Europe, as sum-
marized by Schulenberg and Starflinger [16]. The core design is based on coolant
heat-up in 3 steps. Additional moderator for the thermal-neutron spectrum is provided
in water rods and in gaps between assembly boxes. The design of the nuclear island
and of the balance of the plant confirms results obtained in Japan, namely, an effi-
ciency improvement up to 43.5% and a cost reduction potential of 20%–30% com-
pared with latest BWRs. Safety features as defined by the stringent European
utility requirements are expected to be met.
Canada is developing a pressure-tube-type SCWR concept with a 625°C core outlet
temperature at the pressure of 25MPa. The concept is designed to generate 1200-MW
electrical power (a 300-MW concept is also being considered). It has a modular fuel-
channel configuration with separate coolant and moderator. A high-efficiency fuel
channel is incorporated to house the fuel assembly. The heavy-water moderator
directly contacts the pressure tube and is contained inside a low-pressure calandria
vessel. In addition to providing moderation during normal operation, it is designed
to remove decay heat from the high-efficiency fuel channel during long-term cooling
using a passive moderator-cooling system. A mixture of thorium oxide and plutonium
is introduced as the reference fuel, which aligns with the GIF position paper on tho-
rium fuel. The safety-system design of the Canadian SCWR is similar to that of the
Economic Simplified BWR (ESBWR). However, the introduction of the passive-
moderator-cooling system coupled with the high-efficiency channel could reduce
significantly the core-damage frequency during postulated severe accidents such as
large-break loss-of-coolant or station black-out events.
Preconceptual designs of three options of pressure-vessel SCWRs with thermal-,
mixed-, and fast-neutron spectrum have been developed in Russia.
Outside of the GIF framework, two conceptual SCWR designs with thermal- and
mixed-neutron-spectrum cores have been established by some research institutes in
China under framework of the Chinese national R&D projects from 2007 to 2012,
covering some basic research projects on materials and thermohydraulics, the core/
fuel design, the main system design (including the conventional part), safety systems
design, reactor structure design, and fuel-assembly structure design. The related fea-
sibility studies have also been completed, and show that the design concept has prom-
ising prospects in terms of the overall performance, integration of design, component
structure feasibility and manufacturability.
Prediction of heat transfer in SCW can be based on data from fossil-fired power
plants as discussed by Pioro and Duffey [17]. Computational tools for more complex
geometries like fuel assemblies are available, but still need to be validated with bundle
experiments. System codes for transient-safety analyses have been upgraded to