さていよいよ本題の、原発が海を温めているかどうかの検討であるが、前回（その４）で述べた対馬海流の各海域への影響を念頭に書き進めて行きたい。
前々回（その３）に掲載した図の一部を、重複するのを承知で、下に示す。
日本海中部と対馬海流の上流部分である日本海南西部の温度変化を比べると、押しなべて見て1970年から2010年までの40年間の温度上昇がこの100年間の温度上昇の差を作っている事が読み取れる。
日本海南西部と東シナ海北部を比べた時、日本海南西部での1970年から2010年までの40年間の温度上昇がやや大きいように見えるが、年次変動が大きくはっきりした傾向は読み取りにくい。
実は、海水面の温度の測定がその海域のどの場所で何か所測られたものであり、どのように平均値を得たものかは皆目分からない。しかし、一応海域全体に均等に分布した地点で測定されたものであるとすると、下記のような推測が成り立つ。
原発からの排水が海水面の温度上昇に寄与しているとすると、先回書いたように、日本海中部での温度上昇の傾向は海域の西側に戻ってくるまで保持される。
一方日本海南西部への原発の排水の影響は殆どが福井沖と石川沖で、影響を受ける観測地点の数は限られていると考えられる。
そのように考えると、島根・福井・石川・新潟の原発からの排水が日本海中部の海水面の温度を日本海南西部よりも2010年（2011年）まで上げていた可能性は十分にある。
Now, let's move on to the main subject of whether or not nuclear power plants are warming the ocean.
A part of the diagram that was published in the previous (Part 3) is shown below, knowing that it is duplicated.
Comparing the temperature changes in the central Sea of Japan and the southwestern part of the Sea of Japan, which is the upper reaches of the Tsushima Current, it can be read that the temperature increase during the 40-year period from 1970 to 2010 makes up the difference in temperature increases during the last 100 years.
When comparing the southwestern Japan Sea and the northern part of the East China Sea, the temperature rise in the southwestern Japan Sea during the 40-year period from 1970 to 2010 appears to be slightly larger than that in the northern part of the East China Sea, but it is difficult to read a clear trend due to large annual variations.
In fact, the measurements of sea surface temperature were taken at several locations in the sea area, so it is not clear how the average value was obtained. However, the following conjecture can be made if the measurements were taken at evenly distributed points in the entire ocean.
If the effluent from the plant is contributing to the rise in sea surface temperature, the temperature rise trend in the central Japan Sea will continue until it returns to the west side of the ocean, as I wrote earlier.
On the other hand, the influence of the plant's drainage to the southwest of the Sea of Japan is mostly off the coasts of Fukui and Ishikawa, and the number of observation points affected by this phenomenon is considered to be limited.
This suggests that effluent from the Shimane, Fukui, Ishikawa, and Niigata plants may have raised sea surface temperatures in the central Japan Sea to a higher level in 2010 (2011) than in the southwestern Japan Sea.
Translated with www.DeepL.com/Translator (free version)
Some corrections were added by the author.
Following sentences are translated with "DeepL" and some correction was added as well as above.
The
calculation for the possibility that wastewater from nuclear power plants could
warm up the sea was done using the power output (generating capacity) as of
2010, and the figure below shows the evolution of power generation from 1970 to
2010 (shown until 2009 in the figure below). It can be read that the increase of
generation from 1980 to 2000 is large.
この図の元のデータはウィキペディア（URLは下記）から取り出した。
そしてこの上昇傾向は上の図で日本海南西部と比べた日本海中部の1970年頃から2010年辺りまでの温度上昇の傾向と（何となく）似ている。
では、それら日本海側の原発群から排出されたエネルギーが実際に海水面の温度を上昇させるほどのものか計算してみた。
計算に用いた元の数値と計算結果は下記のとおりである。
原発からの排出エネルギーは単純に出力を２倍にした。
原発の稼働率はもう少し高いかも知れないが、どこかに65％と言う数値があったので、65％とした。
対馬海流の流量であるが、下記のサイトの中に以下の記述があったので、2.65×106m3/sを用いた。
https://www.data.jma.go.jp/gmd/kaiyou/shindan/sougou/html_vol2/2_2_4_vol2.html
「Fukudome et al.（2010）は、船舶に搭載した超音波式ドップラー多層流速計による1997年2月～2007年2月の観測結果から、対馬海峡を通過する流量は、平均すると2.65×106m3/sで、月平均の最大値は10月で3.10×106m3/s、最小値は1月で2.01×106m3/sであったとしている。」
The
original data for this figure was taken from Wikipedia (URL is below).
This
upward trend is (vaguely) similar to the trend of temperature rise in the
central Japan Sea from around 1970 to around 2010 compared to the southwest
Japan Sea in the above figure.
And
the sea surface temperature in the central Japan Sea has decreased by about 0.4
degrees Celsius (five-year running average) since the plant was shut down in
2011.
Then,
the author calculated whether the energy emitted from the nuclear plants on the
Japan Sea side of the island is actually enough to increase the sea surface
temperature.
The
original value and the results of the calculations are as follows
The
author simply doubled the output of the energy emitted from the plant.
The
plant's operation rate could be a little higher, but I found a value that is said
to be 65% somewhere, so I set it at 65%.
As
for the flow rate of the Tsushima Current, I used 2.65 x 106 m3/s
because I found the following description in the following website
https://www.data.jma.go.jp/gmd/kaiyou/shindan/sougou/html_vol2/2_2_4_vol2.html
Fukudome
et al. (2010) found that the average flow rate through Tsushima Straits was
2.65×106m3/s, with a monthly average maximum value of 3.10×106m3/s
in October and a minimum value of It states that in January it was 2.01 x 106 m3/s.
Here
the author calculated on the basis that nuclear power plant discharges twice
the amount of energy generated by a nuclear power plant.
However,
there is another common explanation saying that a 100KWh power plant discharges
70 t/s of wastewater with a temperature rise of 7 degrees Celsius into the sea.
The
figure below shows a calculation using those values.
Results
are slightly different, but they are roughly the same.
However, there is a significant difference between 0.4°C and 0.0027°C.
The focus is on how much the hot water discharged near the sea surface diffuses, but the discussion on this point will be too long, so the author like to discuss it next time.
