Patent Number: 041535065
Section: claims

1. A method of starting operation of a nuclear reactor in which fresh fuel rods are installed of the type having a plurality of cylindrical oxide pellets and a moisture getter enclosed in an elongated tubular cladding of a zirconium alloy comprising: a first step of increasing fuel power produced by the fuel rods to a fuel power amount below an amount which causes an interaction between the pellets and the claddings in the fuel rods,  a second step of maintaining the fuel power amount below the interaction amount for a predetermined period, and  a third step of increasing the fuel power amount to a desired maximum power level of the nuclear reactor after the predetermined period. 2. The method according to claim 1, wherein the fuel power amount in the first step is greater than an amount which is large enough to heat the surface of the pellets to remove residual H.sub.2 O from the fuel rods. 3. The method according to claim 2, wherein the fuel power amount in the second step is kept constant below the amount which causes an interaction between the pellets and the claddings in the fuel rods for the predetermined period. 4. The method according to claim 3, wherein the predetermined period is a sufficient period to remove the residual H.sub.2 O from the fuel rods. 5. The method according to claim 4, wherein the fuel power amount P(Kw/ft) in the first step is smaller than an amount P.sub.1 (Kw/ft) determined from an equation; EQU P.sub.1 = 366 .times. (G/D) - 1.38, 6. The method according to claim 5, wherein the fuel power amount P(Kw/ft) in the first step is larger than an amount P.sub.2 (Kw/ft) determined from an equation; EQU P.sub.2 = 9.54 - 123 .times. (G/D) - 0.016 T, 7. The method according to claim 1, wherein the fuel power amount P(Kw/ft) in the first step is determined by the inequality EQU P.sub.1 &gt; P .gtoreq. P.sub.2 8. The method according to claim 7, wherein the fuel power amount P is maintained at a constant level for the predetermined period in the second step. 9. The method according to claim 8, wherein the predetermined period in the second step is a sufficient period of time to remove the residual H.sub.2 O from the fuel rods. 10. The method according to claim 1, wherein the first and second steps are effected so as to sufficiently absorb moisture into the moisture getter to minimize fuel rod damage due to hydride localization.