Page 170 - Dynamics and Control of Nuclear Reactors

CHAPTER

13
Boiling water reactors

13.1 Introduction
Numerous Boiling Water Reactors (BWRs) are operated in the U.S. and other coun-
tries. About 30% of the commercial nuclear reactors in the U.S. are BWRs. Several
different generations of BWRs have been built or planned. This chapter addresses the
important common features and their influence on the dynamic characteristics
of BWRs.

13.2 History of BWR design evolution
Unlike PWR development, BWRs have undergone an evolution of designs with sig-
nificant changes along the way. Two experimental boiling water reactors were built
at Argonne National Laboratory to test the viability of this reactor type (Borax-1 in
1953 and EBWR, the Experimental Boiling Water Reactor in 1956).
General Electric (GE) entered BWR development with construction of the Val-
lecitos prototype BWR in 1957. GE then embarked on design and construction of
commercial BWR power plants. As of this writing, seven designs of commercial
power plants by General Electric, some with significant changes from its predeces-
sors, have been built. These are designated as BWR-1 through BWR-6 and ABWR
(Advanced Boiling Water Reactor). A new BWR (the ESBWR or Economic Simpli-
fied BWR) has been designed. The main differences in the various designs are con-
tainment features, forced circulation vs. natural circulation, and in-vessel jet pumps
with flow driven by external pumps vs. integral mechanical pumps. The evolution of
GE power plants is described below:

13.2.1 BWR-1
These were early low-power BWRs (all less than 200 MWe). Three versions were
built and had different design features, but all are designated as BWR-1. Differences
in BWR-1 designs includes direct cycle (reactor steam goes directly to the turbine) or
indirect cycle (reactor steam feeds a separate steam generator) and natural circulation
of water flow into the core region or forced circulation.
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