In order to develop the integrity evaluation technology for aged major components of nuclear power plants, the Japan Power Engineering and Inspection Corporation (JAPEIC) has carried out the project named “Nuclear Power Plant Integrated Management Technology (PLIM)” entrusted by Japanese Ministry of Economy, Trade and Industry since 1996 Fiscal Year (FY). One of the objectives of this project is to establish the method for integrity evaluation of aged Japanese reactor pressure vessels (RPV) by developing the prediction equations of reduction of Charpy V-notch upper shelf energy (USE) due to neutron irradiation embrittlement and the correlation equations between USE and fracture toughness. In order to study the effect of certain chemical elements, such as Cu, Ni, P and Si, and initial USE on irradiation embrittlement, nine kinds of base metal, four kinds of weld metal and one kind of heat affected zone were prepared as test materials. They were irradiated at the OECD Halden test reactor, at three fluence levels (3, 6 and 10x1019n/cm2: E>1MeV) considering total fluence estimated after 48 Effective Full Power Year (EFPY) operation of Japanese PWR plants (2 and 3 loop). Post irradiation Charpy impact tests at the upper shelf region were completed to date. This paper is an interim test report about the reduction of USE in the high fluence region.