Predictive and preventive maintenance technologies are increasingly of importance for the long term operation(LTO)of Light Water Reactor(LWR)plants world-widely.In order for the LTO to be successful with maintaining safety,integrity and reliability,it is essential that aging degradation phenomena should be proactively predicted and properly managed by using adequate R & D and maintenance programs based on the improved predictive capability of the aging phenomena and evaluating their rates of degradation.In this paper,presented are some of the results from the outcome from the Japan Nuclear Regulatory Agency Program based upon the activities by the PMDM Experts Panel meeting for the last 6 years.Prioritization of the topics made by the Experts are based on the three important assessment factors as commonly used in Phenomenon Identification and Ranking Table,PIRT; those three are susceptibility level,knowledge level and confidence level,where the aging degradation phenomenon in LWR structural materials has been proactively evaluated and discussed and significant elicitation was made by the Experts.Some important topics related environment-induced degradation are introduced and discussed.In this presentation,research topics considered necessary for a proactive approach to aging degradation phenomena in LWR structural materials which were discussed at the Proactive Aging Management Experts Panel Meeting of NISA/NRA Project,will be introduced.Several short term research subjects(to be completed or to achieve significant progress within 5 years)and several long term research subjects(to be completed in 5-10 years)were outlined for both PWRs and BWRs with a suggested order of the priority.In this presentation,only long term research subjects will be demonstrated.Although some topics may have been already addressed in this 6 years after the program started with a focus extensively by the industry and academia,they are included in the suggested research subjects because of the great concern for the occurrence of the degradation in components that have not yet experienced it.It is also important to continue to promote the systematic elicitation for potential and latent material aging degradation phenomena using the principles developed in the Proactive Aging Management Experts Panel Meeting.Some possible latent/cascade degradation modes have been reviewed and scored and then some typical subjects are demonstrated as possible degradation issues.Most of the issues raised by the Experts Panel Meeting during 2007-2012 are considered as potential latent and/or cascade degradation phenomena and clearly demonstrated by the S-K diagram with confidence scale,demonstrating where more extensive R & D are required for PMDM and LTO.One specific issue of concern is enhancement of mass transfer and consequential materials degradation and enhancement of SCC by hydrogen/vacancy interaction to potentially increase a diffusivity of element to bring enhanced microstructural changes and as a consequence,may result in early materials degradation during LTO and also enhanced oxidation degradation at metal/oxide interface where hydrogen and vacancy formation take place.Need more fundamental research on this topics.