WATER PURITY
DOE-HDBK-1015/2-93
Principles of Water Treatment
CH-04
Rev. 0
Page 28
WATER PURITY
The fewer the contaminants in water, the less corrosion takes place. The methods
of water treatment have been explored previously. This chapter discusses how
water purity is quantified. Measuring the purity helps to keep treatment effective.
EO 1.10
LIST the maximum conductivity and approximate
concentration of electrolyte for each level of purity for
makeup water.
Water Purity
The water used in a nuclear facility must be of a purity level that is consistent with the overall
objectives of chemistry control in the facility.
There are a number of ways in which pure water is obtained, including distillation systems and
pretreatment systems similar to those mentioned earlier in this module. Regardless of the
method employed, the required purity must be achieved.
Water purity has been defined in many different ways, but one generally accepted definition
states that high purity water is water that has been distilled and/or de-ionized so that it will
have a specific resistance of 500,000 ohms (2.0 micromhos conductivity) or greater. This
definition is satisfactory as a base to work from, but for more critical requirements, the
breakdown shown in Table 3 has been suggested to express degrees of purity.
TABLE 3
Water Purity
Degree of Purity
Maximum Conductivity
Approximate Concentration
(µmhos/cm)
of Electrolyte, mg/1
Pure
10
2 - 5
Very Pure
1
0.2 - 0.5
Ultrapure
0.1
0.01 - 0.02
Theoretically Pure
0.054
0.00
