duanearnold


The “Race” to Resolve the Boiling Water Reactor Safety Limit Problem

, director, Nuclear Safety Project

General Electric (GE) informed the Nuclear Regulatory Commission (NRC) in March 2005 that its computer analyses of a depressurization event for boiling water reactors (BWRs) non-conservatively assumed the transient would be terminated by the automatic trips of the main turbine and reactor on high water level in the reactor vessel. GE’s updated computer studies revealed that one of four BWR safety limits could be violated before another automatic response terminated the event.

Over the ensuring decade-plus, owners of 28 of the 34 BWRs operating in the US applied for and received the NRC’s permission to fix the problem. But it’s not clear why the NRC allowed this known safety problem, which could allow nuclear fuel to become damaged, to linger for so long or why the other six BWRs have yet to resolve the problem. UCS has asked the NRC’s Inspector General to look into why and how the NRC tolerated this safety problem affecting so many reactors for so long. Read more >

Bookmark and Share

Benny Hill Explains the NRC Approach to Nuclear Safety

, director, Nuclear Safety Project

The Nuclear Regulatory Commission’s safety regulations require that nuclear reactors be designed to protect the public from postulated accidents, such as the rupture of pipes that would limit the flow of cooling water to the reactor. These regulations include General Design Criteria 34 and 35 in Appendix A to 10 CFR Part 50.

Emergency diesel generators (EDGs) are important safety systems since they provide electricity to emergency equipment if outside power is cut off to the plant—another postulated accident. This electricity, for example, would allow pumps to continue to send cooling water to the reactor vessel to prevent overheating damage to the core. So the NRC has requirements that limit how long a reactor can continue operating without one of its two EDGs under different conditions. The shortest period is 3 days while the longest period is 14 days. Read more >

Bookmark and Share

Nuclear Plant Containment Failure: Isolation Devices

, director, Nuclear Safety Project

Disaster by Design/Safety by Intent #32

Disaster by Design

Containment structures at nuclear power plants have multiple purposes. Containments protect vital safety equipment from damage caused from external events like high winds and the debris they can fling. And containments protect nearby communities against radiation released from reactor cores damaged during accidents. Read more >

Bookmark and Share

Remote Control at Nuclear Power Plants

, director, Nuclear Safety Project

Disaster by Design: Safety by Intent #18

Disaster by Design

Disaster by Design/Safety by Intent #17 covered command and control problems at nuclear power plants that undermined safety. Remote control is required at nuclear power plants to provide capabilities when the control room has to be abandoned. This commentary covers remote control and some of its problems. Read more >

Bookmark and Share

Duane Arnold: The Safety Upgrade that Downgraded Safety

, director, Nuclear Safety Project

The Nuclear Regulatory Commission (NRC) sent a special inspection team to Duane Arnold Energy Center (Palo, Iowa) on October 20, 2014, after workers discovered debris floating on the surface of this boiling water reactor’s torus. They found the coating that had been applied to protect the metal wall of the torus from corrosion was sagging in some places. Deficiencies in the coating could result in the torus wearing out and failing.

The NRC was additionally concerned that debris created by the degraded coating could clog the pipes that emergency pumps use to draw water from the torus and use it to cool the reactor core and containment during an accident. The NRC determined that the increased risk of reactor core meltdown caused by the degraded coating material clogging the emergency pumps warranted a White finding, the third most serious severity level in its Green, White, Yellow, and Red process. Read more >

Bookmark and Share