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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

Beyond-Design-Basis Events

Following the 2011 tsunami and accident at Fukushima-Daiichi in Japan, the nuclear power industry has embarked on a significant effort to evaluate the effect of beyond-design-basis (BDB) events, particularly earthquakes, tsunamis, and floods, on the safety of nuclear power plants.What are BDBs? Beyond-design-basis (BDB) events (sometimes also labeled BDBE) are accident sequences that have such a low probability of occurrence that they were not part of the original plant design. BDB events can be subdivided into two general categories: Internal events, and external events.Internal events include accidents or malfunctions such as multiple spurious failures (rather than the classic single-failure criterion), internal fires, ejected missiles larger than considered in design, chemical reactions and possibly explosions, multiple operator errors, etc.External events can in turn be subdivided into two categories: Man-made, and natural phenomena hazards (NPHs). Man-made events could be accidental or malevolent. BDB NPHs are natural phenomena of a magnitude larger than the...
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Seismic Evaluation of Stacked Spent Nuclear Fuel Casks and Support Structure for Dynamic Stability and Increased Floor Loads

Seismic Evaluation of Stacked Spent Nuclear Fuel Casks and Support Structure for Dynamic Stability and Increased Floor Loads
Unloading of spent nuclear fuel at nuclear utilities typically involves removing spent fuel from the spent fuel pool and placing it in casks for interim on-site storage. During unloading, some utilities use what is known as a “stacked cask” configuration in which a transfer cask is temporarily stacked on top of a storage cask as illustrated. During the time the casks are in the stacked cask configuration, they must be shown to remain stable during postulated earthquakes and the support structure or floor loads must be acceptable. This evaluation is performed as a response history analysis in the time domain using the general-purpose finite element code ANSYS®. The idealized model consists of shell, solid, beam, contact, spring-damper, and concentrated mass elements. The limiting parameters are the peak displacement near the top of the stack and the maximum floor loads. The response history approach allows the analyst to extract the rocking angles,...
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Nuclear Industry Response to the 2011 Tohoku Earthquake and Tsunami in Japan

Prompt Early Response by Regulators and Industry - Shortly after the March 11, 2011 magnitude 9.0 earthquake and tsunami struck Japan, and damaged the six nuclear power plants at the Fukushima Dai-Ichi site, the US NRC began to follow the situation. The NRC also established a Task Force to develop lessons learned. The Near-Term Task Force (NTTF) Review Insights from the Fukushima Dai-Ichi Accident were published on July 12, 2011, and issued through a Request for Information under 10 CFR 50.54(f) on March 12, 2012.The earthquake and tsunami also struck the three nuclear power plants at the Onagawa site, which is nearer to the epicenter than Fukushima Dai-Ichi, but which was safely shutdown and underwent little damage. The lessons learned from this success are also investigated, but have received less attention than the lessons to be learned from the accident at Fukushima Dai-Ichi.The Industry Organizes its Actions – In response to...
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Pump Trips and Check Valve Closure

Pump Trips and Check Valve Closure
Pump Trips and Check Valve ClosureSystems running multiple pumps in parallel can undergo serious equipment and piping damage during a pump trip caused by a power outage or pump mechanical failure. Uncontrolled reverse flow in the system can occur and if improperly selected check valves are used it can result in pumps running backwards or transient pressure spikes in the system, i.e., water hammer. Water hammer will occur if reverse flow occurs prior closure of the check valve and the effect increases with higher reverse flow velocity. Becht has worked with clients on analysis of the design of their systems, e.g., a water treating facility running multiple 52,000 gpm pumps in parallel, a seawater pump station pumping cooling water through a several mile pipeline to an inland facility and a boiler feed water circulation system for a 3000 psig forced circulation boiler. In a three pump system (two operating and one...
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