Spikes in Emissions from Nuclear Power Stations (NPPs)
Up until very recently, it had proved impossible to obtain information on the time patterns of radioactive emissions from NPPs. Despite requests, UK nuclear utilities and Government regulators repeatedly refuse to publish any time-related data: annual emissions, OK: but not monthly, weekly, daily, or hourly emissions.
Is this important? Yes. I’ve suspected for some time that most nuclide emissions from nuclear reactors are not spread evenly across the whole year but during short refuelling episodes which occur about once a year and which last a few days or so.
These short spikes could explain a matter which has puzzled radiation protection agencies for decades – the reason for the apparent increases in childhood leukemias near NPPs all over the world. Governments have insisted that these increased leukemias could not be caused by radioactive emissions from NPPs as their estimated radiation doses were 100-1000 times too low. But as I will show, these estimates are riddled with uncertainties and they don’t take the time patterns of radioactive emissions into account.
In September 2011, International Physicians for the Prevention of Nuclear War (IPPNW) in Germany released a press notice (http://www.ippnw-europe.org/?expand=707&cHash=8752881e4a) which contained data on half-hourly releases of radioactive noble gases from an NPP for the very first time anywhere in the world.
This is shown in the chart below for 7 days in September 2011. These data were from Gundremmingen NPP – a BWR reactor in Bavaria in Southern Germany. The chart showed that the normal emission concentration (of noble gases) during the rest of the year was about 3 kBq/m³, but during refuelling on September 22 this sharply increased to ~700 kBq/m³ with a peak of 1,470 kBq/m³. In other words, a spike. This data shows that NPPs emit much larger amounts of radioactive noble gases during refuelling than during normal power operation. From the new data, Nuremberg physicist and statistician, Dr Alfred Körblein, estimates that, at its maximum value, the concentration of noble gas emissions during refueling was 500 times greater than during normal reactor operation. He also estimates that about two thirds of the NPP’s annual emissions occur during refuelling.
How was this data released?
In May 2011, German Green MPs entered the Bavarian State Parliament (Landtag) for the first time where they formed the Government in coalition with the Socialist Party (SPD). After several requests, the new Bavarian Government insisted that the state nuclear regulator release non-averaged data on emissions. The (highly reluctant) nuclear regulator was compelled to respond. In other words, the Green MPs obtained the data because they had the political power to force its release: there is a lesson here for British environmentalists.
Why is this data important?
In order to refuel, reactor pressure vessels must be opened up: this releases large volumes of radioactive gases and vapours to the local environment. These include noble gases, H-3 (tritium), carbon-14, and iodine-131. Until now, nuclide amounts had only been published as annual averages throughout the world. Now, non-averaged values have been made available for scientific evaluation for the first time.
Could these spikes explain leukemia increases near NPPs?
Yes. People living near nuclear power stations and downwind from them will be exposed to high doses of radiation during these emissions spikes – much higher than from releases during the rest of the year. Estimates range from 20 to 100 times higher. Recently the UK National Dose Assessment Working Group published guidance on “Short Term Releases to the Atmosphere” http://www.ndawg.org/documents/NDAWG-2-2011_000.pdf. This states that “…doses from the assessment of a single realistic short-term release are a factor of about 20 greater than doses from the continuous release assessment.” An older German study (Hinrichsen, 2001*) indicated that these doses could be a factor of 100 greater. The precise amount will depend on many factors, including source term, proximity to the reactor, wind speed, wind direction, and the diets and habits of local people.
The point is that even before the new data, we didn’t have a good handle on the doses to local people. Official estimates of radiation doses from NPPs contain many uncertainties. This is discussed in the 2004 CERRIE Report (www.cerrie.org) – a UK Government Committee which showed that dose estimates from environmental releases depended on many computer models and the assumptions they contained.The new information on radioactive spikes adds to the uncertainties.
Therefore higher doses from emission spikes could go a long way to explaining the increased incidences of child leukemias near NPPs shown by the KiKK findings. IPPNW Germany warns of the probable health impacts of such large emission spikes. “Especially at risk are unborn children. When reactors are open and releasing gases, pregnant women can incorporate much higher concentrations of radionuclides than at other times, mainly via respiration” said Reinhold Thiel, member of the German IPPNW Board. “Radioactive isotopes inhaled by the mother can reach the unborn child via the blood and placenta with the result that the embryo/ fetus is contaminated (`labelled’) by radioactive isotopes. This contamination could affect blood-forming cells in the bone marrow later resulting in leukemia. This provides a plausible explanation for the findings of the KiKK study published in 2007 and 2008 that under-fives living near NPPs are considerably more at risk of cancer, particularly leukemia, than children living further away” Thiel added.
In the light of the new German data, it is recommended half-hourly emissions data from all UK reactors should be disclosed and that the issue of childhood cancer increases near NPPs be re-examined.
*Hinrichsen K (2001) Critical appraisal of the meteorological basis used in (German) General Administrative Regulations (re dispersion coefficients for airborne releases of NPPs) See Annex D page 9: Radiation Biological Opinion. in http://www.strahlentelex.de/_03_Hauptgutachten_Stevenson–vollstaendig.pdf (in German)