Nuclear safety lobby group the Union of Concerned Scientists has publicised a crane accident that occurred at Browns Ferry Nuclear Plant in Alabama, USA in October 2004.
‘A worker at the plant contacted us about the event. We contacted the company, and the NRC [Nuclear Regulatory Commission], and got nothing. They admitted that the crane had dropped, but refused to provide details,’ explained David Lochbaum, nuclear safety engineer, Union of Concerned Scientists.
So five days after the incident, Lochbaum issued a two-page report on the causes of the accident and the results of the UCS’s enquiries with the plant’s operator, the Tennessee Valley Authority, and the NRC.
‘Neither TVA nor the NRC has publicly issued documentation on this event,’ the report said.
It said that NRC Branch Chief Steve Cahill said that the NRC might not release information about the incident if it had determined that there were no violations of federal regulations.
‘The public needs to understand the cause and consequences of last Sunday’s 32-ton drop relative to the planned movement of 100-ton loads by the same crane,’ it concluded.
The strategy of publishing the report worked, Lochbaum said. ‘When we investigate an incident, we look at what happened and what could have happened. They have done a good job of what happened.’
The Tennessee Valley Authority, the operator of the plant, told Hoist that two of three rigging straps holding a 65,000 lb (29.5t crane trolley) broke a few feet above the floor. The impact damaged the floor and the ceiling below, though as of the middle of January, repairs were in progress. No one was hurt.
The TVA spokeswoman blamed the failure of the sling on ‘the improper installation of a required protective shield called a softener. The force of the drop of one end of the trolley caused a second sling to also fail.’
She said the contractor, Ederer Cranes, was working in an area set aside for storing and lifting heavy loads ‘in order to minimize risk to the plant per industry regulations.’
Jim Nelson, director of sales engineering at Ederer, had no comment, citing a TVA contractual gag order.
Still, Lochbaum says he still has concerns about the implications of the incident.
‘We heard that the hook fell on to a concrete floor right above where there is support for the floor. Had the activity happened a few feet over, could it have gone through the concrete to the floors below?’
‘The hook on its own would not have gone through. But when fully loaded with a 125 ton load, it most likely would have. Is it feasible to alter the load pathway so they don’t run across those vulnerable locations?’
Lochbaum says that he expects more information when a final report is published on the incident, which he expects in February.
