SEDL / STP / STP1295-EB / STP16186S

Properties of an Irradiated Heat-Treated Zr-2.5Nb Pressure Tube Removed From the NPD Reactor

Chow, CK
AECL, Whiteshell Laboratories, Pinawa, Manitoba

Coleman, CE
AECL, Chalk River Laboratories, Chalk River, Ontario

Koike, MH
Power Reactor and Nuclear Fuel Development Corporation, O-Arai Engineering Centre, Ibaraki-Ken,

Causey, AR
AECL, Chalk River Laboratories, Chalk River, Ontario

Ells, CE
AECL, Chalk River Laboratories, Chalk River, Ontario

Hosbons, RR
AECL, Chalk River Laboratories, Chalk River, Ontario

Sagat, S
AECL, Chalk River Laboratories, Chalk River, Ontario

Urbanic, VF
AECL, Chalk River Laboratories, Chalk River, Ontario

Rodgers, DK
AECL, Chalk River Laboratories, Chalk River, Ontario

Pages: 23    Published: Jan 1996

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Abstract

Some pressure tubes in reactors moderated by heavy water have been made from heat-treated (HT) Zr-2.5Nb. One such tube was removed from the NPD nuclear reactor after 20 years of operation. An extensive program was carried out jointly by AECL and PNC to evaluate the condition and properties of this pressure tube. The investigations include irradiation creep, tensile, corrosion, delayed hydride cracking (DHC), fatigue, and fracture properties.

Results show that: (1) the in-reactor elongation rate is much lower and the transverse strain rates are slightly larger than in cold-worked (CW) Zr-2.5Nb tubes; (2) the tensile properties, hydrogen pickup, threshold stress intensity factor for DHC initiation, DHC velocity, and fatigue crack growth rates were similar to those of the CW Zr-2.5Nb material; (3) the fracture toughness of this tube, as measured by curved compact toughness specimens and burst tests, is slightly higher than the CW tubes. The results were also compared with other heat-treated Zr-2.5Nb materials irradiated in the Fugen reactor.

The tube was in excellent condition when removed from the reactor and would have been satisfactory for further service.