Inhibiting stress corrosion cracking in the primary coolant circuit of a nuclear reactor
First Claim
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1. A method of inhibiting stress corrosion cracking in a pressurized water nuclear reactor, comprising the steps of:
- (a) circulating coolant water through the primary cooling circuit of a pressurized water nuclear reactor in contact with nickel base alloys comprising at least about 60 w/o nickel, about 13-30 w/o chromium and about 0.3-12 w/o iron,(b) maintaining the coolant water composition atabout 1-2500 ppm boron,about 0.1-10 ppm lithium, andabout 15-75 cc (STP) hydrogen/kg water,(c) maintaining the coolant water pH between about 5.2 and about 7.4 at 20°
C. and conductivity between about 1 and 30 μ
S/cm at 20°
C.; and
(d) adding zinc to the coolant water in amounts sufficient to maintain the zinc concentration between about 5 and about 1000 ppb.
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Abstract
A primary coolant circuit for cooling a nuclear reactor has wetted mechanically stressed nickel base alloy components such as Alloy 600 tubes in steam generators having oxidized surfaces comprising 1-10 w/o zinc, which tubes are inhibited against primary water stress corrosion cracking. The crack initiation times may be delayed by a factor of two in pressurized water nuclear reactors.
22 Citations
20 Claims
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1. A method of inhibiting stress corrosion cracking in a pressurized water nuclear reactor, comprising the steps of:
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(a) circulating coolant water through the primary cooling circuit of a pressurized water nuclear reactor in contact with nickel base alloys comprising at least about 60 w/o nickel, about 13-30 w/o chromium and about 0.3-12 w/o iron, (b) maintaining the coolant water composition at about 1-2500 ppm boron, about 0.1-10 ppm lithium, and about 15-75 cc (STP) hydrogen/kg water, (c) maintaining the coolant water pH between about 5.2 and about 7.4 at 20°
C. and conductivity between about 1 and 30 μ
S/cm at 20°
C.; and(d) adding zinc to the coolant water in amounts sufficient to maintain the zinc concentration between about 5 and about 1000 ppb. - View Dependent Claims (2, 20)
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3. A method of inhibiting stress corrosion cracking of nickel alloy components in a steam generator in a primary coolant circuit of a nuclear reactor, comprising the steps of:
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oxidizing the surfaces of components disposed in a steam generator in a primary coolant circuit of a nuclear reactor which comprise at least about 60 w/o nickel, about 13-30 w/o chromium and about 0.3-12 w/o iron; introducing zinc into the top 50 Angstroms of the oxidized surface to produce a zinc concentration therein of at least 1 w/o; and circulating primary coolant through the circuit at a temperature greater than about 330°
C. - View Dependent Claims (4, 5, 6, 7, 8)
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9. A nuclear reactor having a primary coolant circuit with mechanically stressed components wetted by a primary coolant, which components are fabricated from an alloy comprising at least about 60 w/o nickel, about 13-30 w/o chromium and about 0.3-12 w/o iron and have oxidized surfaces wetted by the primary coolant comprising about 1-10 w/o zinc (as determined by electron spectroscopy) in their top 50 Angstroms, the oxidized surfaces of the components at a temperature of at least about 330°
- C.
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10. A steam generator in a primary coolant circuit of a nuclear reactor having mechanically stressed components wetted by a primary coolant;
- which components are fabricated from an alloy comprising at least about 60 w/o nickel, about 13-30 w/o chromium and about 0.3-12 w/o iron and have oxidized surfaces wetted by the primary coolant comprising about 1-10 w/o zinc (as determined by electron spectroscopy) in their top 50 Angstroms.
- View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
Specification