Fukushima Daiichi Unit

Filburn, S. Bullard, Three Mile Island, Chernobyl and Fukushima, 

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At Fukushima Daiichi Unit 1, an anticipated 920 MW of energy would be transferred to the sea every hour while the plant was operating at full-power (given fliat it would produce 460 MW of electric power, at a level of one third efficiency (Van Wylen and Sonntag, 1973), twice the energy would be rejected versus the electricity produced). If we assume that a 90 °F sea water temperature is the maximum that can be allowed for marines life safety, it is easy to calculate the minimum pumping power required for this process. It turns out that at full power operation, the Fukushima Daiichi sea water pumps would need to move about 220,000 gal/min to sufficiently cool the turbine exhaust steam. 

Anon., 2015a. Roof removed from Fukushima Daiichi Unit 1 Cover. [Online]. Available at http // www.wor1d-nuc1ear-news.org/RS-Roof-removed-from-Fukushima-naiichi-unit-l-cover-0510155.html. [Accessed 28 April 2016]. 

Hoshi, H., Hirano, M., 2012. Severe Accident Analyses of Fukushima Daiichi Units 1 to 3, Tokyo JNES. 

According to the European Nuclear Society, as of the year 2012, there were 435 nuclear power plants operating around the world. With an installed electric net capacity of about 368 GW, these reactors were running in 31 countries. The country with the largest nuclear capacity is the United States with 104 power reactors followed by France (58), Japan (50, though by May 2012, all of these had been temporarily taken out of commission because of concern over the Fukushima Daiichi nuclear plant accident), and the Russian Federation (33). As of 2012, there were 63 nuclear power plants with a total installed capacity of 61 GW under construction in 15 countries. 

The six units of the Fukushima Daiichi plant were numbered sequentially 1 through 6. Units 1 through 4 were arranged north to south. Unit 5 was just to the north of Unit 1, and Unit 6 was to the north of Unit 5 (Fig. 7.1). Thus, from the north to south, the sequence of reactor units was 6-5-1-2-3-4. The total linear distance between the northern point of Unit 6 and the most southern tip of Unit 4 was less than 1 mile. All six units were aligned parallel to the coastline and approximately 35-100 m from the water s edge (Anon., 2012b). 

In the nearly 5 years since the 2011 Fukushima disaster, considerable research has been undertaken to determine the extent of the damage sustained by each Fukushima Daiichi reactor. Although the entire Daiichi site has been so heavily contaminated by radiation that TEPCo does not plan to restart any of the six units, it is considered vital to determine the cause and effect of each reactor s demise. Figuring out what precisely led to the failures at Fukushima can inform on current best practices and can help future plants make design changes to avoid similar catastrophes. 

TEPCo has since replaced the cover over the reactor building and reinforced suspect areas. It has finished the process of removing the spent fuel assemblies from the Unit 4 s spent fuel pool, along with 202 unused fuel assemblies. The spent fuel assemblies have been removed from the spent fuel pool and are now located in a large commonly shared spent fuel pool on the Fukushima Daiichi site. The removal... 

Unit 4 does not contain highly radioactive melted fuel elements and could theoretically be restarted. However, because of the significant radiation throughout the Fukushima Daiichi site, it will not rejoin the Japanese electric grid. The current plan is to decommission and demolish Unit 4 after the highly radioactive components (chiefly the reactor vessel) have decayed to sufficient levels to allow work to proceed safely and efficiently. 

TEPCo, 2013. Regarding the Decommissioning of Units 5 and 6 at Fukushima Daiichi Nuclear Power Station. Tokyo TEPCo. 

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