Heavy water reactors tube-type

Figure VIII-1 shows a simplified schematic diagram of the nuclear steam supply system with the Package-Reactor. The concept resembles a calandria-type pressurized heavy water reactor (e.g., the FUGEN advanced thermal reactor (ATR) or CANDU reactors) since all these employ pressure tubes. But the Package-Reactor is somewhat different from the ATR or the CANDU. The Package-Reactor employs natural circulation with two-phase flow for core cooling and has no recirculation pumps. The height of the pressure tubes of the cassettes is required to be as low as possible to attain a compact unit. Two-phase flow with high void fractions similar to BWRs is adopted to attain natural circulation with a cassette height of 6 m and a fuel rod length of 3.65 m.

The variety of heavy water reactors which exist may be classified on the basis of coolant (D2O, H2O, organic liquid, or CO2 gas) and of basic design (pressure tube or pressure vessel). The subdivisions of reactor types constructed to date, with examples of each, are illustrated in Fig. 10.1. 

This section provides a comparison of power reactors built in the UK with the Soviet RBMK. But it is worth recollecting that, elsewhere in the world, other types of power reactors are in use. The most widely built reactor is the Pressurised Water Reactor (PWR) but the second is the Boiling Water Reactor (BWR), a light water reactor in which, like the RBMK, steam is generated in the core and passed to the turbines in a direct cycle. Light (i.e. ordinary) water is used as coolant and moderator. The Canadian industry has developed the CANDU series of reactors, with limited export to India, etc., which have many pressure tubes to retain the coolant, as in the British SCHWR and Soviet RBMK, but are heavy-water-cooled and moderated. 

The Indian PHWR is a pressure tube type reactor using heavy water moderator, heavy water coolant (in a separate high pressure high temperature system) and natural uranium oxide fuel. 

The dominant type of HWR is the pressure tube heavy water-cooled, HWM reactor as defined by the CANDU and Indian series of reactors. In the following section, the characteristics of the CANDU 6 reactor are used to describe the important features of these reactors. 

In the previous sections, several reactor designs using heavy water moderation are briefly described. Based on the pressure tube boundary conditions, the fuel channel designs can be divided into three types ... 

Reactor type Steam-generating heavy water moderator (SGHWM). Direct cycle pressure tube... 

III-43. Reactors using heavy water (deuterium oxide) as a moderator, a coolant or both have the potential for the same type of accidental release of radioactive material as the corresponding LWRs described above. For a pressure tube reactor, the analyses for loss of coolant accidents need to include ruptures of the pressure tubes as well as header or pipe breaks. Note that... 

The reference fuel for the pressure-tube type of SCWR is a mix of thorium and plutonium (which is extracted from the spent light water reactor (LWR) fuel). On average, the weight percentage of plutonium is 13% in the fuel (Wojtazek, 2015). With the high neutron economy of the heavy water moderator, other fuel mixes can also be accommodated. Studies have demonstrated the feasibility of using low enriched uranium (LEU) of 7% (Yetisir et al., 2012) a mix of LEU at 7.5% with Th a mix of transuranics at 21 wt% with Th (Winkel et al., 2013) or a mix of Pu at 8%, Th, and U (at 2 wt%) extracted from the SCWR fuel (Magill et al., 2011). 

CAN DU A type of Canadian heavy-water-moderated pressure tube natural uranium reactor. The name is derived from Canadian, deuterium (i.e. heavy water) and uranium fuel. 

Once-through, heavy water moderated, supercritical-pressure light water cooled pressure-tube-type reactor (1959)... 

Heavy Water Moderated, Light Water Cooled, Once-Through Pressure-Tube Type Reactor (GE Hanford, 1959)... 

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