*9.1.2. Solution description*

Scheme of joint work of heavy water reactor with gaseous coolant and Rankin cycle steam turbine, which is based on full use of fission energy (including neutron moderation energy) and three stepped steam entering to turbine, is suggested in the paper [26].

First feature of the solution is based on heat emission to the steam in Rankin cycle, which is made not in a single process, but several with different temperature intervals.

The second feature allows avoiding presence of steam with high specific humidity on exit stage blades of turbine. Good parameters are achieved at maximal steam temperature 500 °C and maximal pressure 20.0 MPa.

Scheme of coolant ducts and steam loop of heavy water channel reactor with gaseous coolant is shown at figure 12. Differences of this scheme from other solutions are usage of neutron moderation energy in Rankin cycle for water of steam loop heating, separation of coolant duct on four ducts, which supply with energy re-heater and water evaporator, separate steam overheaters. Coolant ducts for heating and water evaporation can be water ducts.

Neutron moderation energy transfer to water in Rankin cycle is realized with use of vessel of reactor design with greater than atmospheric pressure, but less than maximal pressure in coolant duct. It allows having moderator with temperature greater than water heated in Rankin cycle and decrease thickness of duct walls.

Separation of overheaters ducts allows decreasing of danger of hermetization loss of steam loop with high pressure. Actions for sequence avoiding of hermetization loss is made to duct with small portion of reactor power (~20 %). Reactor scheme at figure 12 gaseous coolant duct, which is linked to high pressure steam duct, has vessel, which supplies decrease of maximal pressure at accidental steam leakage to coolant (volume of steam is limited) and increase time of pressure growth in coolant duct at such leakage (work condition of automatics becomes better).

Besides this separation optimizes energy expenses for coolant pumping by use of temperature differential in corresponding external heat exchangers.

**Figure 12.** Scheme of coolant ducts and steam loop of heavy water channel reactor with gaseous coolant.
