Electrochemical monitoring of vessel penetrations
First Claim
1. A method for assessing deterioration of penetrations traversing a vessel wall of a nuclear reactor pressure vessel defining an enclosure for an electrolyte, comprising the steps of:
- instrumenting at least one of the penetrations by installing a probe, the probe having a plurality of electrodes disposed in an array and positioned adjacent and electrically insulated from metal defining a penetration wall, the probe including conductors coupled individually to respective ones of the electrodes and a conductor coupled to the metal defining the penetration wall such that the penetration wall functions as a working electrode at distinct positions adjacent the respective electrodes;
exposing both the electrode and the penetration wall to the electrolyte in the enclosure;
monitoring electrical activity between the electrode and the penetration wall to develop a signal representing at least one of electrochemical potential, electrochemical impedance, and current passing through the electrolyte between the electrodes and the penetration wall, said electrical activity varying with corrosion of the penetration wall at said distinct positions; and
,assessing deterioration of the penetration wall as a function of the electrical activity.
2 Assignments
0 Petitions
Accused Products
Abstract
Stress-corrosion damage is monitored in penetrations traversing the wall of a vessel containing an electrolyte, such as a nuclear reactor pressure vessel containing a coolant. The vessel wall has tubular penetrations for coupling external devices to internal structures of the vessel while maintaining a pressure barrier, such as control rod guides and sensor signal cables. The penetrations are subject to stress-corrosion damage, especially adjacent welds affixing the tubes to the vessel head. One or more of the penetrations is provided with a probe forming with the tube an electrochemical sensor cell, including an electrode exposed to the electrolyte together with the surface of the penetration. The electrode and the surface are otherwise insulated, and a plurality of electrodes can be arrayed for monitoring distinct localized areas. The electrodes are wired to a detector circuit developing signals as a function of electrochemical activity due to stress and corrosion, indicative of corrosion of all the penetrations. Electrochemical potential, impedance, current, and particularly noise levels in these signals are detected and read out for assessing deterioration of the penetration surface as a function of the electrochemical activity.
-
Citations
17 Claims
-
1. A method for assessing deterioration of penetrations traversing a vessel wall of a nuclear reactor pressure vessel defining an enclosure for an electrolyte, comprising the steps of:
-
instrumenting at least one of the penetrations by installing a probe, the probe having a plurality of electrodes disposed in an array and positioned adjacent and electrically insulated from metal defining a penetration wall, the probe including conductors coupled individually to respective ones of the electrodes and a conductor coupled to the metal defining the penetration wall such that the penetration wall functions as a working electrode at distinct positions adjacent the respective electrodes; exposing both the electrode and the penetration wall to the electrolyte in the enclosure; monitoring electrical activity between the electrode and the penetration wall to develop a signal representing at least one of electrochemical potential, electrochemical impedance, and current passing through the electrolyte between the electrodes and the penetration wall, said electrical activity varying with corrosion of the penetration wall at said distinct positions; and
,assessing deterioration of the penetration wall as a function of the electrical activity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A stress-corrosion monitoring apparatus for a nuclear reactor, comprising:
-
a reactor vessel arranged to enclose a quantity of nuclear fuel and a coolant forming an electrolyte, the reactor vessel having at least one wall traversed by a plurality of penetrations for coupling external devices to internal structures of the reactor vessel, the penetrations defining conduits and being subjected to stress-corrosion damage due to operation of the nuclear reactor; an array comprising a plurality of electrochemical sensors mounted in at least one of the penetrations, the electrochemical sensors each having an electrode insulated from a surface of the at least one of the penetrations and being exposed together with said surface to the electrolyte during operation of the nuclear reactor, said surface and said electrode forming an electrochemical sensing cell wherein said surface functions as a working electrode at a distant area of the surface cooperating with said electrode of the respective electrochemical sensor such that each said electrochemical cell is responsive to localized corrosion of the surface at the distinct area; signal conductors coupled to the electrode and to the surface of said at least one of the penetrations, the signal conductors developing voltage and current signals as a function of electrochemical activity leading to the stress-corrosion damage; a detector circuit coupled to the signal conductors and being operable to encode data representing at least one of electrochemical potential, electrochemical impedance, and current passing through the electrolyte between the electrode and the surface with said localized corrosion of the surface; and
,means for reading out said data for assessing deterioration of the penetration wall as a function of the electrochemical activity. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
-
Specification