Advantages
1. The major advantage of this reactor is that the fuel need not be enriched.
2. The reactor vessel may be built to withstand low pressure, therefore, the cost of the vessel is less.
3. No control rods are required, therefore, control is much easier than other types.
The moderator can be kept at low temperature which increases its effectiveness in slowing down neutrons.
5. Heavy water being a very good moderator, this type of reactor has higher multiplication factor and low fuel consumption.
6. A shorter period is required for the site construction compared with PWR and BWR.
Disadvantages
1. The cost of heavy water is extremely high (Rs. 300/kg).
2. The leakage is a major problem as there are two mechanically sealed closures per fuel channel. Canadian designs generally are based or recovering high proportion of heavy water leakages as absolute leak-tightness cannot be assured.
3. Very high standard of design, manufacture inspection and maintenance are required.
4. The power density is considerably low (9.7 kW/litre) compared with PWR and BWR, therefore, the reactor size is extremely large.
Even though CANDU-type reactors look promising in future, light water reactors all over the world proved more efficient than heavy water and in fact only 36 out of 529 power reactors in the world are based on heavy water.
