Zirconium based alloy of low irradiation growth, method of producing the same, and use of the same

A tubular member of an angular shape made of a zirconium based alloy plate of low irradiation growth which member has a length not less than 4 m, containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, characterized in that said alloy plate has <0001>

• orientation of crystals of hexagonal Zr, which <0001>
• orientation is substantially random, said <00001>
• orientation (Fl value) in a longitudinal direction with respect to opposed faces of said tubular member being substantially equal to each other so that an amount of bow per length of 4 m by neutron irradiation of 35 GWd/t degree of burn-up on taking-out is not more than 2.16 mm.

A fuel channel box made of zirconium based alloy containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, said alloy having crystal orientation of hexagonal Zr in which <0001>

• orientation (Fl value) with respect to longitudinal direction ranges from 0.20 to 0.35, with Fl values with respect to opposed faces of said tubular member being substantially equal to each other so that an amount of bow per length of 4 m by neutron irradiation of 35 GWd/t degree of burn-up on taking-out is not more than 2.16 mm.

A method of producing a tubular member of angular shape made of a zirconium based alloy of low irradiation growth, comprising the steps of locally heating into a .beta. single phase temperature range the tubular member of said zirconium alloy containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, by use of continuous induction-heating, and forcibly cooling the heated portion by use of a cooling medium, characterized in that said heating is performed for a short period of time in said .beta. single phase temperature range together with rapid cooling performed thereafter so that <0001>

• orientation (Fl value) of hexagonal Zr with respect to longitudinal direction of the tubular member ranges from 0.20 to 0.35, wherein a difference in temperature between the opposed faces of the tubular member with respect to said heating is sufficiently small so that a difference (.DELTA.Fl) in Fl values between the opposed faces of the tubular member is not more than 0.025.

A fuel channel box of a tubular member of angular shape formed by welding two channel-shaped members made of zirconium based alloy, characterized in that said alloy has crystal orientation of hexagonal Zr in which <0001>

• orientation (Fl value) with respect to longitudinal direction of the tubular member ranges from 0.20 to 0.35, the difference (.DELTA.Fl) in said Fl between the opposed faces of the tubular member being not more than 0.025, the whole surface of said channel box being provided with oxide coating formed by autoclave treatment.

A fuel assembly comprising fuel rods each provided with fuel pellet in a fuel cladding tube, a channel box receiving a plurality of pieces of the fuel rods, a spacer for partitioning the fuel rods received in the channel box, and upper and lower grids located respectively at the upper and lower portions of the channel box, characterized in that said channel box is made of a zirconium based alloy containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, said alloy having crystal orientation of a hexagonal Zr in which <0001>

• orientation (Fl value) with respect to longitudinal direction of said alloy ranges from 0.20 to 0.35, difference in said Fl between the opposed faces of said channel box being not more than 0.025.

A fuel assembly comprising a long, tubular channel box provided therein with a fuel body having uranium fuel, a fuel rod receiving said uranium fuel, a lower tie plate supporting fuel rod and a spacer, characterized in that said channel box made of a Zr based alloy has crystal orientation of a hexagonal Zr in which <0001>

• orientation (Fl value) with respect to longitudinal plate direction of the channel box ranges from 0.20 to 0.35, difference (.DELTA.Fl) in the Fl values between the opposed planes of said channel box being not more than 0.025, each of .beta.-phase Zr grains having no subboundary in it.

A method of producing a tubular member of angular shape made of a zirconium based alloy containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, comprising the steps of locally heating successively the tubular member of the zirconium based alloy in a .beta. single phase temperature range, and forcibly cooling the locally heated portion, characterized in that said heating is performed by passing the tubular member continuously in a high-frequency induction heating coil of plural windings, and said cooling is performed by jetting a cooling medium through a cooling nozzle provided at a rear of said coil, said method further comprising a step of controlling heating temperature of opposed faces of said tubular member so that said alloy has crystal orientation of hexagonal Zr in which <0001>

• orientation (Fl value) in longitudinal direction of said tubular member ranges from 0.20 to 0.35 and so that a difference (.DELTA.Fl) in Fl values between the opposed faces of the tubular member is not more than 0.025.

A method of producing a tubular member of angular shape made of a zirconium based alloy containing not more than 5 wt % Sn and/or not more than 5 wt % Nb, and not less than 90 wt % Zr, comprising the steps of locally heating successively the tubular member of the zirconium based alloy in a .beta. single phase temperature range, and quenching the locally heated portion by forcibly cooling the locally heated portion through a cooling medium, said quenching being effected plural times, said method further comprising a step of controlling heating temperature of opposed faces of said tubular member so that said alloy has crystal orientation of hexagonal Zr in which <0001>

• orientation (Fl value) in longitudinal direction of said tubular member ranges from 0.20 to 0.35 and so that a difference (.DELTA.Fl) in Fl values between the opposed faces of the tubular member is not more than 0.025.