Experience of surveillance schemes adopted for magnox steel reactor pressure vessels

Abstract

Surveillance or monitoring schemes are recognised to be an important part of any strategy to demonstrate that reactor pressure vessels used in civil nuclear power stations are operated within a safe regime. In the paper the authors describe the experience obtained from the surveillance schemes adopted for the UK's magnox nuclear power stations that were constructed with C–Mn steel reactor pressure vessels. These power stations were constructed in the late 1950s and 1960s and the last ceased generating in 2006. During the lifetime of the fleet with steel pressure vessels, there were developments in testing, observed changes in properties and understanding of radiation damage process that challenged the safety cases to support the operation of the stations. At the time the reactors were designed the concept of fracture toughness was only beginning to be investigated yet, during the lifetime of the stations, fracture toughness testing was successfully adopted as an input to fracture mechanics based assessment of the steel vessels. Over the operating life, a series of challenges emerged that were successfully addressed, including both hardening and non-hardening embrittlement, the latter due to impurity phosphorous segregation in weld metal and contributions from thermal nuclear embrittlement. These challenges led to the adoption of sophisticated statistical techniques to assess changes in embrittlement properties of the most critical construction material – submerged arc weld metal. A large scale sampling and testing programme of submerged arc weld metal removed from a decommissioned reactor pressure vessel validated the assessment process. As a result of successfully addressing these, and other challenges when the last two steel pressure vessel stations closed in December 2006, they had achieved lifetimes of nearly 40 years.     

Research on network integration technology of observation stations

According to the phenomenon of "four more"and"four low "problems in the observation stations,the surface-based meteorological observing system can't adapt to the change of the adaptive observation equipment and reduce of business intensification. A station integrated system is proposed,w hich can be configured,connected and extended to all kinds of observation equipment. And the integrated processor is designed,supporting a variety of communication interface standards. Flexible configuration,connection and expansion betw een conventional and new type of meteorological observation equipment are supported. It is capable for online calibration and maintenance of observation equipment. The effectiveness of automatic observation equipment is totally achieved to provide basic information support for disaster prevention and mitigation and national economic development.     

Precise trajectory control of a redundant flexible manipulator on a space platform

In this paper, we propose a trajectory control method for a redundant flexible space manipulator with slewing and deployable links on a space platform. This method consists manipulator tip position feedback with a transposed Jacobian matrix and local vibration control. We newly derive the Jacobian matrix for a flexible manipulator considering link deformation with the assumed modes method. Simulation results show the effectiveness of this method. We use dynamics consisting of an order N algorithm for N bodies, based on the non-recursive Lagrangian approach, to simulate the dynamics of an orbiting manipulator with an arbitrary number of slewing and deployable flexible links.