Patent Number: 
Section: claims

1. A method of judging practical conditions for use of an ordered structure alloy under an irradiation environment, comprising:preparing an irradiated state diagram that expresses for the ordered structure alloy a relation of a degree of long range order S to a variable R of an irradiated state of the ordered structure alloy, related to a damage rate and an irradiation temperature, on basis of an evaluation formula related to an effect of irradiation on the degree of long range order of the ordered structure alloy under irradiation environments by using as parameters, a first threshold value Sth1 at which the degree of long range order begins to decrease, under irradiation, at a rate greater than a rate at which the degree of long range order decreased prior to the first threshold value having been reached, a second threshold value Sth2 at which the degree of long range order is nearer to reaching equilibrium than the degree of long range order was prior to the second threshold value having been reached and after decrease of the degree of the long range order which began at the first threshold value Sth1, and the degree of long range order in an equilibrium state Seq;for irradiation conditions under which the ordered structure alloy is to be used, calculating an R-value, and corresponding to the R-value, finding an S-value, an Sth1-value, an Sth2-value, and an Seq-value; andcomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, to thereby predict a damage level and a variation condition of the damage level of the ordered structure alloy under the irradiation environment. 2. The method according to claim 1, whereincomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, with 0<Seq-value<Sth2-value<Sth1-value<1, and considering a magnitude relation of these values, results in the following judgments being made(i) when Sth1-value<S-value, the ordered structure alloy is in an ordered state and has a large degree of long range order, corresponding to a low damage level,(ii) when Sth2-value<S-value<Sth1-value, the ordered structure alloy is in a transition process from an ordered state to a disordered state and the degree of long range order decreases, corresponding to a damage level of the alloy fluctuating greatly and tending to increase rapidly,(iii) when Seq-value<S-value<Sth2-value, the ordered structure alloy is in a process of reaching a disordered state and an amount of a decrease in the degree of long range order is small while the degree of long range order is small, corresponding to a damage level of the alloy being large but fluctuating little, and(iv) when S-value<Seq-value, the ordered structure alloy is in a disordered state and the degree of long range order is small, corresponding to a high damage level. 3. The method according to claim 2, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 4. The method according to claim 1, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 5. A method of judging practical conditions for use of an ordered structure alloy under an irradiation environment, comprising:preparing an irradiated state diagram that expresses for the ordered structure alloy a relation of a damage rate to a reciprocal of an irradiation temperature on basis of an evaluation formula, related to an effect of irradiation on a degree of long range order S of the ordered structure alloy under irradiation environments, by using as parameters, a first threshold value Sth1 at which the degree of long range order begins to decrease, under irradiation, at a rate greater than a rate at which the degree of long range order decreased prior to the first threshold value having been reached, a second threshold value Sth2 at which the degree of long range order is nearer to reaching equilibrium than the degree of long range order was prior to the second threshold value having been reached and after decrease of the degree of the long range order which began at the first threshold value Sth1, and the degree of long range order in an equilibrium state Seq;for irradiation conditions under which the ordered structure alloy is to be used, calculating a value of the reciprocal of an irradiation temperature of the ordered structure alloy, and corresponding to the value of the reciprocal of the irradiation temperature, finding an S-value, an Sth1-value, an Sth2-value, and an Seq-value; andcomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, to thereby predict a damage level and a variation condition of the damage level of the ordered structure alloy under the irradiation environment. 6. The method according to claim 5, whereincomparing the S-value, the Sth1-value, the Sth2-value, and the Seq-value, with 0<Seq-value<Sth2-value<Sth1-value<1, and considering a magnitude relation of these values, results in the following judgments being made(i) when Sth1-value<S-value, the ordered structure alloy is in an ordered state and has a large degree of long range order, corresponding to a low damage level,(ii) when Sth2-value<S-value<Sth1-value, the ordered structure alloy is in a transition process from an ordered state to a disordered state and the degree of long range order decreases, corresponding to a damage level of the alloy fluctuating greatly and tending to increase rapidly,(iii) when Seq-value<S-value<Sth2-value, the ordered structure alloy is in a process of reaching a disordered state and an amount of a decrease in the degree of long range order is small while the degree of long range order is small, corresponding to a damage level of the alloy being large but fluctuating little, and(iv) when S-value<Seq-value, the ordered structure alloy is in a disordered state and the degree of long range order is small, corresponding to a high damage level. 7. The method according to claim 6, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms. 8. The method according to claim 5, whereinthe degree of long range order S is equal to the probability that composed sublattices are correctly occupied by constituent atoms minus the probability that that composed sublattices are not correctly occupied by constituent atoms.