After university, Large moved to the United States to work on U.S. nuclear weapons projects. This required him to take U.S. citizenship, but due to the risk of
Vietnam War conscription he returned to the UK. During the 1980s, Large was an advisor on nuclear issues to Shadow Secretary of State for Energy
Tony Blair. In 1986, he founded the London-based consulting engineers Large & Associates, which specialised in analysis of and reporting on failure of engineering systems, particularly in the nuclear field, which at one time employed up to 40 people. Large was a Chartered Engineer, a Fellow of the
Institution of Mechanical Engineers and a Fellow of the
Royal Society of Arts. Large formed and led the nuclear risk assessment team involved in raising of the sunken and severely damaged Russian nuclear submarine
Kursk in 2001 - the world's first successful recovery of a nuclear powered submarine. Large was among those awarded a medal by the
Rubin Central Design Bureau for Marine Engineering for the recovery. He provided technical evidence in the
Friends of the Earth legal action over the failure of the steam generators of the Southern California
San Onofre Nuclear Generating Station in 2013. His evidence to the
Atomic Safety and Licensing Board significantly contributed to their decision that the novel proposed operational changes to restart the reactors constituted the regulatory definition of "tests or experiments", requiring the obtaining of an operating license amendment. This led to the operators deciding to "permanently retire" the reactors. He reported upon the so-called 'carbon anomaly' that resulted in the temporary shutdown and resumption to power generation under restrictive conditions of 18 French nuclear power plants in 2016-17. Separately, he advised on related quality control issues in Japan.
Critical reviewer At times, Large was critical of the
nuclear power industry, and was commissioned by
Greenpeace and other national and international
NGOs to provide technical analysis on nuclear issues. In 1985 Large was invited by House of Commons
Environment Committee to submit evidence on environmental issues associated with radioactive waste at the UK's irradiated fuel reprocessing works at
Sellafield. He provided the Committee with a technical note on the breakaway corrosion of
Magnox nuclear fuel, demonstrating the then hitherto undisclosed highly unstable
pyrophoric reaction. Resulting from this disclosure, he provided evidence on the secrecy practised by the UK nuclear industry. In 2003 Large submitted a paper for publication to the
Institution of Mechanical Engineers about the danger of a terrorist attack on UK nuclear installations. The paper was passed to the UK security services and then suppressed on the advice of the
UK government, although the work was subsequently published overseas in revised form. In November 2014, following a spate of overflights of French nuclear power plants by unmanned aerial vehicles (
UAV), Large provided evidence to the French Parliament (in the open session of
Office parlementaire d'évaluation des choix scientifiques et technologiques relating to the vulnerabilities of plants to drone intrusion. The Large & Associates' report on the drone activity, commissioned by Greenpeace France, remains confidential but aroused considerable media speculation. ==Death==