Fukushima Daiichi reactors

The Fukushima Daiichi reactors are six boiling water reactors (BWR) of an early 1960s design supplied by GE, Toshiba, and Hitachi with power ranges from 460 MWe to 1,100 MWe. They came into commercial operation between 1971 and 1975. Four units (1-4) are of Mark-I type containment, which is the first generation of BWR design (Fig. 24.1). At the time of the accident, the units and central storage facility contained the fuel assemblies as shown in Table 24.1.

Подпись: 24.1 Mark-I type BWR (equivalent to units 1-4 of Fukushima Daiichi NPP) [1]. Spent fuel —————

pool

Reactor service — floor

Concrete reactor building

Reactor pressure vessel

Primary containment drywell

Suppression pond wetwell

Table 24.1 Numbers and types of fuel assemblies [3]

Location

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

Central

storage

Fuel type

UOx

UOx

UOx/MOX

UOX

UOx

X

О

D

UOx/MOX

Core-loaded fuel assemblies

400

548

548

0

548

764

0

New fuel assemblies

100

28

52

204

48

64

N/A

Spent fuel assemblies

292

587

514

1,331

946

876

6,375

MOX = Mixed Oxide fuel. N/A = not available.

Tanabe [ 4] has estimated that the unit 1 core contained 78.3 tons of uranium

dioxide, 32.7 tons of zirconium, 12.5 tons of steel, 590 kilos of boron carbide and

1 ton of inconel.

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