This Summary combines two recent assessments undertaken by Large & Associates on the replacement steam generator problems and proposals to restart at least one of the two nuclear power plants at the San Onofre Nuclear Generating Station. The first assessment considers the proposals of the plant operator and licensee, Southern California Edison to restart Unit 2, operating the plant at 70% of its thermal rated power. The second assessment considers whether the NRC’s Confirmatory Action Letter was anther form of de facto license amendment.
SummaryVulnerability of French NPPs to Accidental Aircraft Crash
Y Broses Heneiddio A’i Dylanwad Ar Ddiogelwch A Pherfformiad Wylfa
Mae’r Adolygiad hwn yn ystyried sut y gellid disgwyl i’r broses heneiddio effeithio ar berfformiad a diogelwch yr orsaf ynni niwclear yn Wylfa.
Yn achos Wylfa, mae’r broses heneiddio yn cyfeirio at nifer fawr o ddeunyddiau a rhannau o’r adweithyddion. Mae rhai o’r prosesau heneiddio hyn yn rhai cymharol syml ac yn rhai yr ydym yn eu deall yn weddol dda; mae eraill yn fwy cymhleth sydd heb eu deall yn llwyr eto. Gyda threigl amser, daw yn fwy a mwy anodd, os nad yn fwy annibynadwy i geisio rhagweld pa broblemau sy’n deillio o heneiddio sy’n debygol o godi yn awr ac yn y dyfodol. Yn wir, wrth i oes yr adweithyddion ymestyn dros yr 20 neu 25 mlynedd a fwriadwyd ar eu cyfer yn wreiddiol, mae’n rhaid dibynnu fwyfwy ar archwilio deunyddiau a rhannau’r adweithyddion a dim ond trwy wneud hyn y gellir canfod beth yn union yw effeithiau’r broses heneiddio. Y broblem yma yw nad yw’r adweithyddion yn Wylfa yn cynnwys nodweddion sy’n ein galluogi i archwilio’r holl rannau hynny sy’n debygol o gael eu heffeithio wrth iddynt heneiddio.
Review
Degradation of AGR Graphite Moderator Cores
The graphite core of an AGR nuclear power plant is a central nuclear safety component. The core is a loose stack of several thousand graphite bricks assembled to form a facet-sided cylinder of about 12m diameter by 10m height. The core serves to moderate (slow) the neutrons initiating fission in the nuclear fuel but in doing so its materials properties change and there is a pronounced loss of weight of graphite. This Review examines the importance of graphite radiolytic ageing to the nuclear safety case.
ReviewTHORP Feed Clarification Cell Leak – Corroded Dissolver Pipework
Following discrepancies in the inventory and nuclear material balance controls at the front end of the irradiated fuel thermal oxide reprocessing plant (THORP) at Sellafield, on 20 April 2005 a remotely operated camera revealed a significant quantity of highly radioactive liquor in the sump of Cell 220. In total and over several months previously, approximately 84m3 of liquor, in the form of a nitric acid solution of fuel and fission products, had built-up in the sump, leaking from a feed pipe connection to one of two accountancy vessels located in the cell.
Review