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Original Message
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120 Quadrillion becquerels of radioactive cesium into North Pacific Ocean from Fukushima Exceeds Chernobyl
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by Christina MacPherson
Japan Gov’t-funded Study: Fukushima has released up to 120 Quadrillion becquerels of radioactive cesium into North Pacific Ocean — Does not include amounts that fell on land — Exceeds Chernobyl total, which accounts for releases deposited on land AND ocean
(MAP) [link to enenews.com] 1 July 14,
Scientific Reports (Nature.com), Mar. 4 2014: The total amount of decay-corrected 134Cs in the [subtropical] mode water was an estimated about 6 PBq [petabecquerels, i.e. 6 quadrillion becquerels] corresponding to 10–60% of the total inventory of Fukushima-derived 134Cs in the North Pacific Ocean. […] The decay corrected ratio of 134Cs/137Cs in soils has been calculated to be 1.0, which suggests that the total amounts of 134Cs and 137Cs released from FNPP1 were equivalent. […] the total amount of Fukushima-derived radiocesium in the North Pacific remains uncertain, because it has been difficult to obtain sufficient samples of water, especially from subsurface and deep waters, in the vast North Pacific Ocean […] Estimates of the total 134Cs released to the North Pacific Ocean ranged from 10 PBq (direct discharge of 4 PBq + atmospheric deposition 6 PBq) to 46 PBq (16 + 30 PBq). Thus, the 6 PBq inventory accounts for 10–60% of the total release. However, the total inventory in the subtropical region derived from the activity in STMW [Subtropical Mode Water] may be underestimated, because CMW probably carried the radiocesium into the subtropical region, too […] The estimated inventory in the subtropical region (6 PBq or 10– 60% of the total inventory) is probably a lower limit of estimation because contribution of CMW [Central Mode Water] was not counted.
[...]
Funding: “This work was partially supported by a Grant-in-Aid… from the Ministry of Education, Culture, Sports, Science and Technology of Japan”
[End snip]
[link to nuclear-news.net]
SOUTHWARD SPREADING OF THE FUKUSHIMA-DERIVED RADIOCESIUM ACROSS THE KUROSHIO EXTENSION IN THE NORTH PACIFIC
The accident of the Fukushima Dai-ichi nuclear power plant in March 2011 released a large amount of radiocesium into the North Pacific Ocean. Vertical distributions of Fukushima-derived radiocesium were measured at stations along the 149°E meridian in the western North Pacific during the winter of 2012. In the subtropical region, to the south of the Kuroshio Extension, we found a subsurface radiocesium maximum at a depth of about 300 m. It is concluded that atmospheric-deposited radiocesium south of the Kuroshio Extension just after the accident had been transported not only eastward along with surface currents but also southward due to formation/subduction of subtropical mode waters within about 10 months after the accident. The total amount of decay-corrected 134Cs in the mode water was an estimated about 6 PBq corresponding to 10–60% of the total inventory of Fukushima-derived 134Cs in the North Pacific Ocean.
Introduction
The massive Tohoku earthquake and consequent giant tsunamis on 11 March 2011 resulted in serious damage to the Fukushima Dai-ichi nuclear power plant (FNPP1)1. Radiocesium (134Cs and 137Cs) derived from the damaged FNPP1 caused radioactive contamination of the islands of Japan and the North Pacific Ocean2. Most of the Fukushima-derived radiocesium deposited on land has remained in soils. Within about 100 km of the FNPP1, where contamination was serious, the radiocesium in soils has been measured intensively3. The decay-corrected ratio of134Cs/137Cs in soils has been calculated to be 1.0, which suggests that the total amounts of 134Cs and 137Cs released from FNPP1 were equivalent. The relationship between the radiocesium activity in the soil and the air dose rate derived from airborne monitoring has provided a map of the density of radiocesium deposition throughout the islands of Japan4. The sum of the deposition, the total inventory of 137Cs (or 134Cs) on the islands of Japan, has been estimated to be 2.4 PBq5. However, the total amount of Fukushima-derived radiocesium in the North Pacific remains uncertain, because it has been difficult to obtain sufficient samples of water, especially from subsurface and deep waters, in the vast North Pacific Ocean, except from the coastal area near the FNPP16, 7, 8.
Radiocesium isotopes were released into the North Pacific through two major pathways, direct discharges of radioactive water and atmospheric deposition. About ten days after the earthquake, Tokyo Electric Power Company and the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) began marine monitoring in the coastal area within about 50 km from the FNPP16, 7, 8. These high-frequency measurements have facilitated an evaluation of the total amount of radiocesium derived from the directly discharged radioactive water. The values estimated in several studies were in the range 4–6 PBq1, 9, 10, 11, 12, 13, although one study calculated the value to be 27 PBq (12–41 PBq)14. The total direct release of 27 PBq was somewhat of an overestimate11, 15 and resulted in activities in a model ocean that were unrealistically high compared to activities measured in the real ocean16. However, radiocesium activities measured during a cruise in June 2011, mainly in the open ocean17, indicated that the total activity of 137Cs (or 134Cs) directly discharged to the ocean equaled 11–16 PBq18, 19.
A large portion of the radiocesium released to the atmosphere from the FNPP1 was deposited onto the North Pacific Ocean, because the winds over Japan usually blow from the west in the spring20. However, the small number of observational data in the open ocean cannot estimate the total oceanic deposition directly.
Alternatively, that could be calculated indirectly from the total amount of radiocesium released to the atmosphere, which was derived primarily from measurements on land. Estimations of the total amount released to the atmosphere range widely, from 8.8 to 37 PBq1, 5, 9, 11, 14, 21, 22, 23, 24, 25. The 2.4 PBq deposited onto the islands of Japan suggests that most of the remaining radiocesium, 6.4–35 PBq, found its way into the North Pacific through atmospheric deposition. Atmospheric models have estimated independently the total oceanic deposition to be 5.8–30 PBq5, 9, 11, 12, 23, 25, similar to the range of 6.4–35 PBq. However, the deposition on land has been overestimated in many of the models.
Efforts to obtain observational data from the open ocean have continued. The marine monitoring from March 2011 by MEXT or the Nuclear Regulation Authority was extended eastward to the 144°E meridian in August 20117. Radiocesium measurements in the area further east have been reported in several publications8, 17, 26, 27, 28, 29, 30, 31. Seawater sampling from April 2011 during commercial ship cruises has produced a valuable dataset across the North Pacific28, although as in many other previous studies, most of the samples were collected only at the surface. In June 2011 vertical profiles of the Fukushima-derived radiocesium were measured at stations along 147°E between 34.5°N and 38°N, and it was found that the radiocesium had penetrated to a depth of about 200 m roughly two months after the disaster17. Although these observational data are still insufficient for direct estimation of the total amount of radiocesium in the whole North Pacific, these data can be used to validate ocean model simulations that have predicted vertical and horizontal spreading of the radiocesium in the ocean13, 15, 16, 25, 32, 33.
Here we report the vertical distributions of the Fukushima-derived radiocesium at stations along 149°E between 10°N and 42°N in the winter of 2012, about ten months after the accident. Our preliminary reports, which have already been published31, 34, revealed that (1) the Fukushima-derived radiocesium activity was highest in the transition area between the subarctic and subtropical regions and (2) the radiocesium was transported southward across the Kuroshio Extension (KE) through subsurface layers. In this study, we discuss the causes of the southward spreading of the radiocesium based on temporal changes in the activity of surface waters.
Secondly, we have estimated the vertical water-column inventory of radiocesium. These results will contribute to determination of the total inventory of radiocesium and will facilitate prediction of the spreading of the Fukushima-derived radiocesium in the North Pacific Ocean in the future.
We measured both 134Cs and 137Cs activities (Methods).
The ratio of decay-corrected134Cs/137Cs in samples in which the 137Cs activity was higher than 20 Bq m−3 was about 0.95. The small excess of137Cs was derived from another source of 137Cs, global fallout due to the nuclear bomb testing in the 1950s and 1960s35. The excess 137Cs in surface waters (about 1.5 Bq m−3) in the winter of 2012 corresponds to bomb-produced137Cs activities (about 1.9 Bq m−3) in surface water of the North Pacific before the accident (about 2.4 Bq m−3 in 2000)36. Therefore, only results for 134Cs, which is a unique tracer of the FNPP1 accident, are presented in later sections.
[link to citizenperth.wordpress.com]
RAID ON THE DIET PRESS HALL
Freelance journalists raid the Diet kisha club building in order to properly report the massive protests against the Abe government’s unilateral dismissal of the Japanese Constitution.
Source: Shingetsu News
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[link to citizenperth.wordpress.com]
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