Linking Microstructure to Neutron Irradiation Defects in Advanced Manufacture of Steels

点击翻译按钮获取中文摘要

The UK plans to build a new fleet of nuclear power plants starting with two units at Hinkley Point in Somerset. The UK government has also recently announced in the autumn 2015 statement that £250M will be set aside for in innovative nuclear technologies. More specifically it has stated that the UK will invest in small modular reactor designs. The large reactors and many small modular reactor designs are based around a reactor type called a pressurised water reactor. These reactor designs have a steel reactor pressure vessel to enclose the nuclear fuel and act as a key barrier to the release of radiotoxic materials to the environment. The integrity of the vessels is paramount to the safety and continued operation of the reactor. Unfortunately, neutron irradiation from the nuclear fuel damages the steels over their 40-60 year design life. Understanding the role of neutron damage to these steels is therefore key to continued operation beyond the design life. This programme of work will study commonly used reactor pressure vessel forging grade steels (A508 class 3), under neutron irradiation damage, at the OPAL test reactor, at Lucas Heights in Australia. The steels will be manufactured by processes not commonly used in nuclear reactors i.e. hot isostatic pressing (HIP) of powdered material and then welded using electron beams (EB). These new manufacturing processes could potentially be used to manufacture parts for the reactor pressure vessels of future small reactor designs. As yet there is no information on how changing the manufacturing routes from arc welding of forged material to EB welding of HIPed material will change the neutron irradiation response of the material. In this case the chemistry of the material remains unchanged so the key variable is the so-called "microstructure" of the material.It is planned to irradiate samples, at the OPAL reactor, for up to 1 year, to achieve doses of neutron embrittlement equivalent to 40-60 years reactor operation. The irradiated material will then be mechanically tested, in hot cells, at the Australian Nuclear Science and Technology Organisation before material is shipped to the new Materials Research Faclility at UKAEA Culham site in the UK. Here, it will be prepared for state-of-the-art characterisation, by atom probe tomography on the new LEAP 5000 atom probe recently installed at Oxford University, Chemi-STEM transmission electron microscopy at Manchester University, together with atomic scale models developed at Imperial College London and Manchester University. The project will also have management and input from the National Nuclear Laboratory and Rolls-Royce and international links to the University of New South Wales, University of California Santa Barbara and Oak Ridge National Laboratory.The overall output from this work will be much improved mechanistic understanding and models of how neutron irradiation effects steels manufactured by HIP and EB welding, lead to a new generation of engineers in the UK who can perform work on irradiated materials and help direct the use of such technologies for the building of future small reactor designs. It will also be a crucial driver in the effort to rebuild the physical and knowledge based infrastructure, for dealing with neutron irradiated steels, that has been missing for a generation in the UK.