More on Nuclear Energy Facilities, Summer Heat and Water Use

The following guest post was submitted by NEI Media Manager, Mitch Singer.

Perhaps it’s asking too much in today’s media climate (no pun intended), but it would’ve been nice if Ginger Zee refrained from making the flippant comment on America This Morning that cooling ponds near nuclear plants are “either getting too low or too warm for the plants to function safely.” Ginger’s wrong on a number of accounts.

Safety is paramount to the nuclear industry and all plants have contingency plans in place to adjust to extreme weather conditions and continue operating, albeit at a lower electrical power output. All nuclear power plants operate under their respective states’ water discharge permits and when the water’s ambient temperature reaches a certain level the plant’s power output must be lowered. Thus, they continue to “function safely.”

The Browns Ferry Nuclear Plant in Alabama operated by the Tennessee Valley Authority (TVA) provides a great example of how in spite of extreme heat and higher-than-normal water temperatures a nuclear plant can continue to produce electricity. TVA’s Ray Golden explained it clearly to me in a conversation earlier today:

In the summers of 2010 and 2011 TVA had to reduce electrical power output at all three Browns Ferry units up to 50 percent (approximately 500 megawatts each) to maintain downstream river temperatures within the thermal compliance limits associated with its State of Alabama water discharge permit.

Browns Ferry draws water from the Tennessee River to cool plant equipment. In the process of cooling this equipment the water gets heated. This heated water is sent to a series of seven, very large cooling towers. The cooling towers use large fans to cool the water before returning it to the river.

When the river’s upstream ambient temperature rises to 90 degrees, TVA’s water permit does not allow any additional increase in water temperature. In order to comply with this regulation, at times Browns Ferry’s power output has to be lowered.  By lowering power output we reduce the discharge temperature.

During periods of extended high river temperatures and low rainfall, the company’s environmental compliance model requires the need to take prompt action to avoid exceeding any permit limits.

TVA returns Browns Ferry and other fossil-powered generating stations to full power when temperatures and river flow conditions are adequate for full power operation without challenging river temperature permit limits.

TVA has been proactively working on a project to address the issue of summer river temperatures and the requirement to reduce Browns Ferry power output.

In the summer of 2012, TVA completed construction of a seventh cooling tower which provides additional river water cooling during the hot summer months. The seventh tower is twice the size of the existing cooling towers and uses state-of-the-art engineering and equipment to maximize cooling capability. With cooling tower #7 in operation the need to reduce Browns Ferry’s power output has been eliminated so far this summer.

TVA returns Browns Ferry and other fossil-fueled plants to full power when temperatures and river flow conditions are adequate for full power operation without challenging river temperature permit limits.

Unfortunately, there are too many reports such as this morning’s where the issue of context is never considered. The fact is that ANY power plant, including coal and natural gas, that generates electricity through steam turbines and uses cooling water to condense the steam would face similar circumstances under drought conditions.

As my colleague David Bradish pointed out in his July 11 blog post, the National Oceanic and Atmospheric Administration reported that the month of June experienced “170 all-time high temperature records being broken or tied throughout the country.” Yet, America’s nuclear plants operated at an average of 90 percent capacity, as they have done so for most of the past decade. That’s a record of consistency that would make baseball great Cal Ripken take notice.

The Brown's Ferry nuclear energy facility in Alabama. Pic courtesy of TVA.

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U.S. Nuclear Plants Humming Along During June 2012 Heat Wave

Yesterday, the National Oceanic and Atmospheric Administration reported that the month of June experienced 170 all-time high temperature records being broken or tied throughout the country. They also reported that the first half of 2012 has been the warmest first half period on record back to 1895. As such, we wanted to share that most all of the U.S. nuclear plants were humming along at full power during June, helping provide electricity to air conditioners to keep all of us cool during these hot times.

Below are three charts breaking out the daily availability data from the Nuclear Regulatory Commission which we aggregated based on the North American Electric Reliability Council they belong to. You can find the list of plants and their region on page 4 of this report.

The following chart shows a daily average of the 104 nuclear units. Overall, the U.S. fleet was running at a steady average availability of 90.5% during the last four weeks.

And the last chart shows the NERC regions, how many reactors belong to each region in the U.S., and their average availability.

It’s worth pointing out that two of the regions, MRO and WECC, had  a lower average availability factor of 82% and 68%, respectively. This was mainly because three of the 14 reactors in those regions have been in long-term shutdown.

Average availability in MRO is lower because Fort Calhoun is down (1 unit out of 6). If we take Fort Calhoun out of the calculation, the plants that are running in that region have an average availability of 98.2%.

Similarly in WECC, the two San Onofre units are down. If we take San Onofre out, the other six reactors in the region have an average availability of 90.3%.

And in SERC and FRCC, Crystal River (1 unit out of 38) has also been down. Take Crystal River out of the equation, and the plants running have an average availability of 95.5% (vs. 93.0% for all 38).

Performance of Other Technologies

There isn’t similar daily availability data for other technologies to compare their performances to nuclear during the same heat wave. But to give an idea of how they perform annually, below is a chart of average capacity factors for various power sources.

August is typically the summer month for peak nuclear generation. As the summer progresses, we’ll see nearly all nuclear units online by then.

Though this year’s trend isn’t looking promising, hopefully temps will be a bit cooler for everyone during the rest of the summer. Stay cool.

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NOAA Looks at the Waters Near Fukushima Daiichi

The American National Oceanic and Atmospheric Agency sent a research vessel boat to Japan last April to study the waters near the Fukushima Daiichi facility and assess the impact of radioactive isotopes released into the water by the plant. The international team of researchers found isotopes of cesium, which was expected, and silver, which was not expected. (Radioactive silver has a half-life of 250 days).

The conclusion in the abstract: “Radiation risks due to these radionuclides are below those generally considered harmful to marine animals and human consumers, and even below those from naturally occurring radionuclides.”

And that’s striking. Especially interesting was this:

To be comparable just to doses from ²¹⁰Po, ¹³⁷Cs levels in fish would need to range from 300 to 12,000 Bq·kg⁻¹ dry weight, some 1–3 orders of magnitude higher than what we observed ≥30 km off Japan. Thus, radiation risks of these isotopes to marine organisms and human consumers of seafood are well below those from natural radionuclides.

And this:

Further, we can calculate an external dose to humans if immersed/swimming in these waters of <0.01 μSv·d⁻¹ at ¹³⁴Cs and ¹³⁷Cs levels of 1,000 Bq·m⁻³, which is <0.3% of the average Japanese dose of about 4 μSv·d⁻¹ from all radioactivity sources.

And the conclusion:

Finally, these levels are several orders of magnitude lower than those used in one study that assumed exposure to the most heavily impacted water discharged from the Fukushima NPPs [nuclear power plants] to predict marked reproductive effects and possible mortality in marine biota.

Biota is the flora and fauna of a region.

These are very heartening findings. Still, the authors are careful not to overstate the case:

Ultimately, though the radionuclide levels of ¹³⁷Cs and ¹³⁴Cs offshore are currently low with respect to human health effects, any assessment of radiation dose should also consider long-term exposure if the NPP remains a continued source of radionuclides (5) and if, as has been reported, coastal sediments are contaminated with multiple radionuclides.

Those “if”s require a different study.

As the samples above show, the paper can be appropriately dense, but still readable by non-experts. Do take  a look at the whole thing.

The NOAA ship Ka'imimoana (Hawaiian for “ocean seeker”) was used for the research described in the paper.

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