CRUD AND GALVANIC CORROSION
DOE-HDBK-1015/1-93
Corrosion
CH-02
Rev. 0
Page 22
CRUD AND GALVANIC CORROSION
A major potential problem is crud. Crud can cause an increase in
background radiation levels. When two dissimilar metals are in close
vicinity, the opportunity for ion transfer is high. The result is a perfect
environment for galvanic corrosion. Because of the numerous types of
materials used in nuclear facilities, galvanic corrosion is a major concern.
EO 1.13
DEFINE the following terms:
a.
Crud
b.
Scale
c.
Galvanic corrosion
EO 1.14
IDENTIFY the five problems associated with the presence or
release of crud into reactor coolant.
EO 1.15
STATE the four causes of crud bursts.
EO 1.16
STATE the two conditions that can cause galvanic corrosion.
EO 1.17
EXPLAIN the mechanism for galvanic corrosion.
EO 1.18
IDENTIFY the two locations that are susceptible to galvanic
corrosion.
EO 1.19
STATE the five control measures used to minimize galvanic
corrosion.
Crud
In addition to the corrosion film, corrosion products in the form of finely divided, insoluble oxide
particles called crud become suspended in the reactor coolant or loosely adhere to metal
surfaces. Crud has several undesirable characteristics. It can be transported throughout the
reactor coolant system. As a result, it can accumulate and foul heat-transfer surfaces or clog
flow passages. The most undesirable characteristic of crud, however, is that it becomes
activated when exposed to radiation. Because crud can be transported throughout the reactor
coolant system, it can collect outside the reactor core, causing radiation hot spots that increase
ambient radiation levels. Hot spots caused by collections of crud may occur at the entrance to
the purification heat exchanger and other areas of low flow velocity. Crud that is loosely
adhered to metal surfaces can suddenly become suspended in the reactor coolant.
