SummaryWorking on an intensive care unit is perceived as stressful. This study investigated occupational stress in staff working on an intensive care unit using the occupational stress indicator. Questionnaires were given to all intensive care staff; the replies were then analysed and compared with normative data. The response rate was 62%. Intensive care unit staff found aspects of their job relating to career and achievement and organisational design and structure more stressful than a normal working population. Their coping strategies differ but the only significantly different measure of adverse outcome was related to personal relationships at work. The job itself was not found to be a significant source of stress. Nursing staff have different sources of stress from medical staff and individuals with partners or children are relatively protected from stress.

Flaw indications have been found in some dissimilar metal nozzle to stainless steel piping welds in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe using Alloy 182/82 weld metal. Due to an unexpected aging issue with the weld metal, the weld becomes susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. This paper represents one of a series of papers which examine the propensity for cracking in a particular operating PWR in the UK. This paper represents an examination of the weld residual stress distributions which occur in four different size nozzles in the plant. Companion papers in this conference examine crack growth and PWSCC mitigation efforts related to this plant. British Energy (BE) has developed a work program to assess the possible impact of PWSCC on dissimilar metal welds in the primary circuit of the Sizewell ‘B’ pressurized water reactor. This effort has included the design and manufacture of representative PWR safety/relief valve nozzle welds both with and without a full structural weld overlay, multiple residual stress measurements on both mock-ups using the deep hole and incremental deep hole methods, and a number of finite element weld residual stress simulations of both the mock-ups and equivalent plant welds. This work is summarized in companion papers [1–3]. Here, the detailed weld residual stress predictions for these nozzles are summarized. The weld residual stresses in a PWR spray nozzle, safety/relief nozzle, surge nozzle, and finally a steam generator hot-leg nozzle are predicted here using an axis-symmetric computational weld solution process. The residual stresses are documented and these feed into a natural crack growth analysis provided in a companion PVP 2010-25162 paper [1]. The solutions are made using several different constitutive models: kinematic hardening, isotropic hardening, and a mixed hardening model. Discussion will be provided as to the appropriateness of the constitutive model for multi-pass DM weld modeling. In addition, the effect of including or neglecting the post-weld heat treatment process, which typically occurs after the buttering process in a DM weld, is presented. During operation the DM welds in a PWR experience temperatures in excess of 300°C. The coefficient of thermal expansion (CTE) mismatch between the three materials, particularly the higher CTE in the stainless steel, affects the stresses at operating temperature. The K-weld geometry used in the steam generator nozzles in this plant combines with CTE mis-match effects to result in service stresses somewhat different from V-weld groove cases.

British Energy (BE) has funded a large work programme to assess the possible impact of primary water stress corrosion cracking on dissimilar metal welds in the primary circuit of the Sizewell ‘B’ pressurised water reactor. This effort has included the design and manufacture of representative pressuriser safety/relief valve (SRV) nozzle welds both with and without a full structural weld overlay, multiple residual stress measurements on both mock-ups using the deep hole and incremental deep hole methods, and a number of finite element weld residual stress simulations of both the mock-ups and equivalent plant welds. Three organisations have performed simulations of the safety/relief valve nozzle configuration: Westinghouse, Engineering Mechanics Corporation of Columbus (EMC2) and the Australian Nuclear Science and Technology Organisation (ANSTO). The simulations employ different welding heat input idealisations, make different assumptions about manufacturing history, and use a variety of different material constitutive models, ranging from simple bilinear kinematic hardening to a full mixed isotropic-kinematic formulation. The availability of both high quality measurements from well characterised mock-ups, and a large matrix of simulations, offers the opportunity for a “mini-round-robin” examining both the accuracy and key solution variables of dissimilar metal weld finite element simulations. This paper is one of a series at this conference that examine various aspects of the BE work programme. It draws together residual stress measurement results and the results of all three simulation campaigns (described in detail in other papers at this conference) to examine the impact of manufacturing history, thermal modelling assumptions, material constitutive models and other key solution variables on the accuracy of residual stress predictions in this dissimilar metal weld geometry.

The natural crack growth analysis (sometimes referred to as advanced finite element analysis (AFEA)) methodology has been developed by the US NRC and the nuclear industry to evaluate the natural crack growth due to primary water stress corrosion cracking (PWSCC) in nickel-based alloy materials. The natural crack growth (or AFEA) methodology allows the progression of a planar crack subjected to typical stress corrosion cracking (SCC)-type growth laws by calculating stress intensity factors at every nodal point along the crack front and incrementally advancing the crack front in a more natural manner. This paper describes the step-by-step procedure enhancements that have been made to the existing AFEA methodology. A significant enhancement was the feature to evaluate axial crack growth, where the crack was contained within the susceptible material. This methodology was validated by performing an AFEA evaluation for the axial crack that was found in the V.C. Summer hot-leg dissimilar metal weld (DMW). Other enhancements to the AFEA methodology include: feature to handle nonidealized circumferential through-wall cracks, mapping of weld residual stress for crack growth, and determination of limiting crack size using elastic-plastic J-integral analysis that included secondary stress (weld residual stress and thermal transient stress) effects.

The Advanced Finite Element Analysis (AFEA) methodology has been developed by the US NRC and the nuclear industry to evaluate the natural crack growth of primary water stress corrosion cracking (PWSCC) in nickel-based alloy materials. The AFEA methodology allows the progression of a planar crack subjected to typical SCC-type growth laws by calculating stress intensity factors at every nodal point along the crack front, and incrementally advancing the crack front in a more natural manner. This paper describes the enhancements that have been made to the existing AFEA methodology. The most significant enhancement was the feature to evaluate axial crack growth where the crack was contained within the susceptible material. In this paper, this methodology was validated by performing an AFEA evaluation for the axial crack that was found in the V.C. Summer hot leg dissimilar metal weld. Other enhancements to the AFEA methodology include; upgrade to the PipeFracCAE© software developed by Engineering Mechanics Corporation of Columbus, feature to handle non-idealized circumferential through-wall cracks, mapping of weld residual stress for crack growth, and determination of limiting crack size using elastic-plastic J-integral analysis that included secondary stress (weld residual stress and thermal transient stress) effects.