Zr-2.5Nb tubeShenzhen Sunrise Metal Industry Co.,Ltd

Zr-2.5Nb tube

Shenzhen Sunrise Metal Industry Co.,Ltd

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E-Mail:sales@sunriseta.comThe Development of Zr-2.5Nb Pressure Tubes for CANDU ReactorsAbstract

The first reactor to use zirconium alloy tubes to contain hot pressurized water as a heat transport medium was the Hanford N reactor in 1962. For this reactor, three companies that had suitable extrusion and cold working equipment were given contracts to produce Zircaloy-2 tubes. All the companies were successful, and tubes from each company were installed in the reactor. When Canada decided to design and build a power reactor (nuclear power demonstration (NPD)), it elected to use the pressure tube concept and gave a contract to one of the companies (Chase Bass) to fabricate the Zircaloy-2 tubes. Douglas Point and Pickering Units 1 and 2 followed NPD, and all used similar Zircaloy-2 pressure tubes. A stronger tube was desired in order to thin the wall and improve the neutron economy. An alloy development program in the USSR had shown that the alloy Zr-2.5Nb looked very promising as a stronger alloy than Zircaloy-2, and both the USSR and Canada developed this alloy and subsequently used Zr-2.5Nb pressure tubes in their reactors. When both the Zircaloy-2 and Zr-2.5Nb pressure tubes were first installed in the reactors, several important properties and characteristics such as hydrogen ingress into the metal from corrosion in water, the enhancement of creep by neutron irradiation, shape change by neutron irradiation, reduction in fracture toughness by neutron irradiation, and delayed hydride cracking were not appreciated. These properties all led to problems during the service lives of the early tubes. Large research programs investigated these properties and showed that the α-grain size, shape, and crystallographic texture, the distribution of the β-phase, the dislocation type, and density as well as the micro-chemistry controlled the in-reactor properties of the tubes. This information enabled the design and operation of the reactors to be changed so that the tubes had satisfactory service lives. In addition, the information was used to fabricate tubes that had much improved properties and service lives. The original paper was published by ASTM International in the Journal of ASTM International, August 2010.

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Zr-2.5Nb pressure tubes, CANDU reactors, fabricationAssessment of Aging of Zr-2.5Nb Pressure Tubes for Use in Heavy Water ReactorABSTRACT The pressure tubes of pressurized heavy water reactor (PHWR) operate under high temperature high pressure aqueous environment and are subjected to fast neutron irradiation. In order to assure the structural integrity of pressure tube during service, it is periodically examined by non-destructive examination (NDE) techniques. A typical Pressurized Heavy Water Reactor (PHWR) consists of few hundred horizontally placed coolant channels. The coolant channel comprises of a Zr-2.5% Nb pressure tube encircled by a Zircaloy-4 calandria tube and four garter spring spacers (Zr-2.5Nb-0.5Cu), which prevents these two tubes to come in contact during their service life. The pressure tube carries the nuclear fuel, high temperature high pressure heavy water coolant and is subjected to fast neutron irradiation. The integrity of pressure tube is central to the safety of PHWRs. To ensure this, they are periodically subjected to in-service inspection by nondestructive examination (NDE) techniques. In this paper detailed study has been done on the operating conditions which lead to degradations in the pressure tube with respect to dimensional changes as a result of irradiation creep and growth, deterioration in mechanical properties due to irradiation embitterment, initiation and growth of new flaws like fretting damage due to debris and fuel element bearing pads. The absorbed hydrogen can also limit the life of a pressure tube due to the degradation mechanisms such as delayed hydride cracking (DHC), hydride blister formation and cracking and hydride embitterment. It is a also one of the regulatory requirement to periodically subject pressure tubes to in-service inspection by employing non-destructive examination techniques. All these aspects have been duly addressed in this paper.
Assessment of Aging of Zr-2.5Nb Pressure Tubes for Use in Heavy Water Reactor (PDF Download Available).