Review of the proof pressure tests of the prestressed concrete reactor vessels at Hartlepool and Heysham nuclear power stations

The results of the statutory proof pressure tests which have been carried out on the four prestressed concrete reactor vessels (PCRVs) at Hartlepool and Heysham nuclear power stations are reviewed. These are the first Advanced Gas Cooled Reactor (AGR) stations in the world to use PCRVs in which the boilers are housed in pods within the vessel walls. A description of the instrumentation used to monitor the vessels during the proof tests is given. Possible sources of instrumentation error are identified and discussed. The comprehensive pre-test checks including load checks and corrosion examinations of some of the vessels' prestressing tendons, assessment of the strain response of each vessel and visual inspection of the vessels' outer surfaces are described. The procedures for each test proper including the preliminary pressurisation to check for leaks, the stage by stage pressurisation, collection of data during the main test, and processing to enable assessment between successive pressurisation stages are described. Variations in ambient temperature and general weather conditions prevailing at each test affected the measured data. These were taken into account when reviewing the results. The tests have shown that the vessels behave similarly, elastically and closely in accordance with predictions. (U.K.)