CANDU – type nuclear reactor natural uranium finds extensive use because

Question

Consider the following statements:

CANDU – type nuclear reactor natural uranium finds extensive use because

1. Heavy water is used both as coolant and moderator.
2. Cost of fuel used is much lower than that used in pressurized water or boiling water reactor.
3. Small leakage of heavy water does not affect the performance of the reactor substantially.
4. Fuel consumption is low because of use of heavy water.    

Which of these statements are correct?

(a) 1,2 3 and 4             (b) 1,2, and 4

(c)1 and 2                    (d)3 and 4