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Reactor Accidents


Fort Calhoun 6-11-11

Updated, Monday, June 27, 2011, 11:30 am.

The situation at Fort Calhoun became more precarious Sunday as OPPD workers punctured the 8-foot water-filled berm protecting the reactor and other essential buildings (although the berm does not protect irradiated fuel stored in dry casks at the site). The berm collapsed and the floodwaters rushed into the area containing the main electrical transformers, flooding the area. The utility cut off offsite power in response, and began running on emergency diesel generators to provide cooling for the reactor--never a good situation.

The Nuclear Regulatory Commission activated its Incident Response Center to keep a closer eye on the events at Fort Calhoun, and NRC Chairman Greg Jaczko is scheduled to visit the site today.

Offsite power apparently has been restored to the site. This article from today's Omaha World-Herald is obviously meant to be reassuring, but also clearly indicates that there will be serious challenges to this reactor and OPPD for a long time to come. And the record so far--including OPPD's failure to take flood issues seriously until forced to by the NRC, and the failure of the berm caused by OPPD's own actions--does not provide comfort that OPPD will be up to these challenges.

This short article from today's Huffington Post includes a new photo of Fort Calhoun. Although it's taken from a different angle than the photo above, it can be used for comparison as to how the flooding has increased. The article indicates that water has begun seeping into the site's turbine building.

Fort Calhoun is about 19 miles north of downtown Omaha, but just a few miles north of the growing Omaha suburbs.

Meanwhile the Cooper reactor (see below), about 80 miles south of Omaha, continues to operate at full power.Water there has not yet reached flood stage, although it is uncomfortably close. As a GE Mark I reactor--a Fukushima clone--there is ample reason to be concerned about Cooper's ability to withstand any challenge to its operations.

June 15, 2011, updated June 22, 2011

Flooding on the Missouri River is threatening Nebraska's Fort Calhoun nuclear reactor, owned and operated by the Omaha Public Power District (OPPD). Above is a photo of the Fort Calhoun site taken June 11, 2011. A brief video of the site on June 14 is available here (the portion showing Fort Calhoun starts at 1 minutes 21 seconds into the video and lasts about 5 seconds, so you may want to pause it).

On June 22, 2011, the U.S. Army Corps of Engineers began releasing a greater volume of water from the Gavins Point Dam upstream of the Fort Calhoun and Cooper reactors (see below for more information on Cooper). This is likely to cause the Missouri River floodwaters to rise further, as are recent heavy rains in South Dakota and continued snowcap melting in Montana. This clearly will be a very long flooding event.

The Fort Calhoun reactor is currently in cold shutdown and has been since April 9, 2011, when it began a refueling outage. The refueling process is complete and the reactor is holding a full complement of fuel--1/3 fresh (unused) fuel and 2/3 older and highly radioactive fuel. The reactor has not been restarted since the refueling outage began.

The Fort Calhoun fuel pool is in the auxiliary building (brown building to the right of the white containment building in photo above). The pool itself is about 30 feet above ground level. The pool currently contains about 670 metric tons of irradiated fuel. About 165 tons of irradiated fuel are stored in dry casks at the site (location in photo above unknown). Together this fuel contains about 100 million curies of radiation, 40% of which is Cesium-137. This single reactor's irradiated waste thus contains more Cesium-137 than has been reported to have been released to date from the four Fukushima reactors.

The reactor site is 1004 feet above sea level. The water level is currently, according to the Nuclear Regulatory Commission, at 1005 feet, 7 inches above sea level and is projected to rise to 1006 feet, 4 inches. This flood stage is projected to last for weeks. However, that projection assumes normal rainfall in the coming weeks and no failure of upstream levees--two factors which could cause a higher flood stage. The utility (Omaha Public Power District) has put an 8-foot rubber flood berm around the plant and believes it can withstand a flood up to about 1010 feet above sea level.

Two significant events have occured at Fort Calhoun since the flood waters began to rise. On June 7, a fire in an electrical switchroom knocked out power, and thus cooling capability, to the fuel pool for about 90 minutes. Utility officials claim it would take 88 hours of loss of cooling for the water to fully boil off. However, since some of the fuel in the pool has been loaded since April 9 and is thus quite hot, this may have been an overly optimistic estimate.

On June 13, sewage from the site's administration building was released into the Missouri River at the rate of 105 gallons per minute. We have been unable to determine how long this release took place. Since the sewage reportedly came from the administration building, it was not likely to have contained radiation.

On June 17, OPPD issued a notice that of a potential flooding vulnerability--a hole in a floor--that could have impacted one safety system. OPPD was expected to seal the hole later that day.

According to an updated entry in Wikipedia: "A flood assessment performed by the Nuclear Regulatory Commission in 2010 indicated that the Fort Calhoun Nuclear Generating Station, "did not have adequate procedures to protect the intake structure and auxiliary building against external flooding events."[6] The assessment also indicated that the facility was not adequately prepared for a "worst-case" flooding scenario. A number of potential flood water penetration points were discovered that could have impacted the raw feed water supply to the cooling system, the axilliary water supply and main switchgear (electrical) room. By early 2011, corrective measures had been implemented.[6]"

Fort Calhoun is a 500 MW Combustion Engineering Pressurized Water Reactor. It received its initial operating license in October 1973, and a renewal of its license in 2003. It is now licensed to operate until August 2033. The Nuclear Regulatory Commission currently considers Fort Calhoun to be one of the three most problematic reactors in the U.S. because of ongoing safety issues at the reactor, and the site has been under enhanced oversight for some time. On June 16, the NRC sent additional inspectors to the site to review flood preparations.

below is a photo of Fort Calhoun under normal conditions.

Fort Calhoun normally

The Cooper nuclear reactor in Nebraska, also on the Missouri River, is also the subject of flooding concerns. Cooper is a GE Mark I reactor, like the reactors that failed at Fukushima. Three workers were exposed to radiation this Spring at Cooper, and in mid-June the utility was cited by the NRC for fire prevention deficiencies. A Notification of Unusual Event--the lowest of the NRC's 4 safety categories--was declared on Sunday, June 19 at the Cooper reactor due to rising floodwaters. At this time, however, the flooding is not expected to challenge the reactor, but much depends on how high the waters reach over the next few weeks.

This 2004 NIRS factsheet on natural disasters and nuclear power includes a section on the 1993 flood on the Missouri River that threatened the Cooper reactor and caused extensive leakage inside the reactor and turbine buildings.

This 1994 Nuclear Regulatory Commission Information Notice (sent to all reactor operators) discusses the 1993 flood at Cooper and the potential effects of such flooding on nuclear facilities.