Civil Engineering Reference
In-Depth Information
1
Reactor core
10
Pre-heater
2
Main coolant pump
11
Feedwater tank
3
High pressure part of turbine
12
Feedwater pump
4
Low pressure part of turbine
13
Interconnecting pipe
5
Generator
14
Cooling water
6
Water separator
15
Cooling -water pump
7
Superheater
16
Cooling tower
8
Condenser
9
Condensate Pump
Fig. 3.17
Functional diagram of a boiling water reactor [
14
]. 1. Reactor core, 2. Main coolant
pump, 3. High pressure part of turbine, 4. Low pressure part of turbine, 5. Generator, 6. Water
separator, 7. Superheater, 8. Condenser, 9. Condensate pump, 10. Pre-heater, 11. Feedwater tank,
12. Feedwater pump, 13. Interconnecting pipe, 14. Cooling water, 15. Cooling-water pump, 16.
Cooling tower
3.3.1 Core, Pressure Vessel and Cooling System of a BWR
The reactor core of BWRs consists of a square array of 784 or 664 so-called
ATRIUM fuel elements, about 3.74 or 3.0 m long for the BWR-1,300 of Kraftwerk
Union and the SWR-1,000 of AREVA, respectively (Table
3.3
). Each fuel element
contains either 10
10 (ATRIUM 10) or 12
12 (ATRIUM 12) fuel rods in a
closed square box of 131
155 mm, the so-called fuel channel
(Fig.
3.18
). The ATRIUM fuel elements have a 3
131 or 155
4 cm central
water channel to achieve a relatively flat power profile across the fuel element [
1
,
6
,
7
,
14
-
16
]. The core and fuel element data of the ABWR of TOSHIBA are given
in Sect.
3.4
. For moderation of the neutrons and cooling of the core, water flows
through the core and is allowed to boil in the upper part of the core. Cruciform
absorber plates (Fig.
3.19
), containing boron carbide or hafnium as absorber
material, are installed in between a set of four square fuel elements. The absorber
plates are moved hydraulically into and out of the reactor core from below.
The fuel rods have claddings of Zircaloy and contain UO
2
pellets with enrich-
ments of about 4.5 % or 5.4 % U-235. The fuel is unloaded after a maximum burnup
of 55,000 or 65,000 MWd/ton. Roughly one quarter of the fuel elements are
3cmor4
