One sees eerie similarities here in Canada to the incestuous, cozy relationship between regulator andutilities in pre-Fukushima Japan.  This has created conditions that are ripe for a nuclear disaster. Operating reactors have barely seen any substantive risk reduction upgrades eight years after Fukushima, hoopla around some minor improvements and closure of regulatory 'Fukushima Action Items' notwithstanding. At less than 0.7 atm(g) design pressure and design leakage \~500 times the 0.1%/day norm in newer PWRs, the multi unit CANDU reactors sport some of the weakest containments; have high steam and air oxidation potential in 10km of low carbon steel feeder piping and twice the Zircaloy of LWRs. Combustible gas detection and mitigation systems are unfortunately designed for Hydrogen instead of Deuterium gas in these PHWRs.  With no reactor pressure vessel to isolate the overheating core debris, the leaky containments become immediate recipients for copious quantities of combustible Deuterium and fission products. Reactor geometriesand interconnected reactors promote combustible gas explosion potential. The pressure relief systems in cooling and moderating systems are dangerously inadequate, resulting likely in containment bypass and vessel failures. Even more dangerous are the unsubstantiated claims being made of near impossibility of off-site releases by clueless, irresponsible management without nay a challenge by the regulators, eager to rubber stamp all industry requests. The life management issues of ageing, elongating, thinning, hydriding, embrittling and deforming pressure tubes is yet to be resolved but these obsolete reactors keep getting ever longer license extensions (over 50% beyond original Pickering pressure tube design life). Proposed engineering fixes that can be undertaken to overcome some critical vulnerabilities are groundlessly rejected in ingrained obdurate industry intransigence against changes. Emergency preparedness by civil authorities has been conditioned for smallest source terms and available response time for mitigation measures irresponsibly exaggerated. A number of early mitigation measures, common to all PWRs, will not work due to an unusually low, below core, placement of Pressurizer that will divert much primary coolant in detriment of potential fuel cooling restoration by re-flooded boilers inducing natural circulation flows. These are signs of impending implosions in Canadian nuclear industry that has avoided resilience engineering.Not likely, but perhapsdisaster can be avoided by a return to the principles, and not mere slogans, of 'safety first'. Right now, an unmitigated station blackout in a CANDU multi-unit station will make Fukushima disaster look like a walk in the park.

*Note : This paper was accepted, peer reviewed and scheduled for presentation at ICONE 27 conference in 2019 but a scheduling conflict prevented my participation. I look forward to discussing my analyses at ICONE28 in 2020.*


Unmet Challenges to Successfully Mitigating Severe Accidents in Multi Unit CANDU Reactors

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

POWER-ICONE - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.