By Takeo Hashizume and Yoshitaka Mukohara*
Environmental impact from 1oC sea temperature rise
Reports of changes in the marine environment have become frequent in recent years. Fisherman everywhere say that they can't catch fish anymore, or that the species of fish they catch has changed. Experts believe these changes have been caused by a rise in sea temperature. It is said that the temperature of Japan's coastal waters has risen by 1oC in the past 10 years.
In comparison with the temperature of the air, variations in the temperature of the sea are small. The sea temperature range over four seasons at Kagoshima (southern Kyushu) is between 15oC and 29oC. Within such a small range a rise of 1oC is very significant. At Kagoshima it is enough to allow tropical fish to survive the winter. As such, it is already upsetting the ecological balance of the marine environment.
We reported in the July 2009 edition of CNIC's Japanese newsletter that monthly water temperature measurements conducted since February 2007 by the Kagoshima Anti-Nuclear Network showed that warm water discharged to sea from Units 1 and 2 of Kyushu Electric's Sendai Nuclear Power Station is being re-circulated through the reactors. In other words, the same water that is taken from the sea to cool the reactors and discharged back to sea as warm water is taken in again and circulated back through the plant. Through observations carried out over a 3-year period, we established that as a consequence of re-circulating warm water in this way the water at the intake location was 2oC higher than the surrounding sea temperature. Due to the higher temperature at the intake point, the temperature of the water at the outlet was raised by 8oC, exceeding the requirement in the safety agreement that the temperature of discharged warm water be raised by no more than 7oC.
The consequences for the marine environment of this careless design error depend on how far the elevated temperatures extend. Kyushu Electric Power Company insists, "The area within which the sea temperature is elevated more than 1oC is mostly around 2 kilometers offshore."
On March 2, 2010 the Asahi Shimbun reported that Kyushu Electric had falsified data related to warm water discharge monitoring results. Kyushu Electric formally submits these monitoring results to Kagoshima Prefecture under the safety agreement between the power company and the prefectural government. The agreement contains an information disclosure clause, so these results are publicly available. We immediately checked the data.
Kyushu Electric carries out marine monitoring 4 times a year, once per season. Sea temperature is shown on isothermal maps. The isotherm for the region of 1oC temperature elevation is invariably drawn within the 2-kilometer offshore zone. However, if one looks carefully, one sees that the region extends beyond the isothermal line drawn on the maps. Kyushu Electric has been deliberately making the area of elevated sea temperature look smaller than it really is.
There have been 30 surveys since 2002. In that time, we confirmed 17 instances of deliberate deception. On some occasions one of the two units was down for inspection. Of the 20 occasions on which both units were operating, there were 10 cases of data falsification.
Clearly there is consistent and deliberate manipulation of the data. If one looks carefully, one finds cases where the isotherm indicating an elevation of 1oC is drawn around regions where the temperature is clearly elevated by 2oC. For example, in figure 2 a 1oC elevation should correspond to 17oC, but the line is drawn at 18oC.
Not 2 km but 5 km
By measuring the maximum region of elevated temperature shown in Kyushu Electric's records for each survey day since 2002, we derived an average figure of 2.4 kilometers. It is debatable whether that fits Kyushu Electric's claim of "around 2 kilometers". However, if rather than using Kyushu Electric's arbitrarily drawn isotherms, one draws isotherms in accordance with actual temperature, one finds that of the 20 cases where both units were operating, on 12 occasions the region of elevated temperature extended beyond the range of Kyushu Electric's monitoring (5 kilometers south). We don't know exactly how far the influence of warm water discharge extended, but using an estimate of 6 kilometers, we derived an average of 4.9 kilometers between April 2002 and August 2009. That is twice as far as Kyushu Electric claims.
Baseline data for Sendai-3 assessment is "around 2 km"
Kyushu Electric is on the verge of constructing a third unit at its Sendai Nuclear Power Station. We take the view that having submitted falsified data, Kyushu Electric should be disqualified from building a new nuclear power plant. However, for the record we have identified the following three key issues.
- Kyushu Electric's plan for the Sendai-3 plant is based on a region of "around 2 km" of elevated sea temperature from warm water discharge from the two existing Sendai plants. Given that the explanation is based on falsified data, the environmental impact assessment process is invalid.
- In fact, the region consistently exceeds 2 kilometers and in 60% of cases it exceeds 5 kilometers.
- The cause of the very high temperature increase is the recirculation of warm water discharge. This recirculation is not taken into account in the environmental assessment for Sendai-3.
Kyushu Electric says blithely that there is no problem, because "The Prefecture's committee has approved [the reports]". At this stage, Kagoshima Prefecture shows no sign of making an issue of it either. However, if Unit 3 is operated under these circumstances, there is no doubt that seawater temperatures will be raised over a wider region than anticipated. The marine environment around Kagoshima will be destroyed.
* Takeo Hashizume and Yoshitaka Mukohara are members of the Kagoshima Anti-Nuclear Network.
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