US 5,154,197 A · Chemical cleaning method for steam generators utilizing pressure pulsing

Abstract

An improved method for removing sludge and corrosion products from the interior of a heat exchanger vessel, such as a nuclear steam generator, which comprises the steps of generating a series of pressure pulses within a liquid chelate-containing chemical cleaning agent after the agent has been introduced into the interior of the vessel to create shock waves in the liquid for dislodging, dissolving and fluidizing sludge and corrosion products. The liquid chemical cleaning agent is removed from the vessel after only about 10 to 70 percent of what would have been its normal residence time without the pressure pulses. The method further includes the steps of simultaneously recirculating the chemical cleaning agent through a filter assembly during the pressure pulsing operation in order to remove fluidized sludge and corrosion products dislodged by the pressure pulsing, thereby affording them no opportunity to resettle back onto the surfaces of the heat exchanger vessel and interfere with the chemical cleaning of the vessel. The method reduces not only the time required for a particular chemical cleaning agent to effectively clean the vessel, but further reduces the number of times such chemicals need to be introduced into the vessel, which in turn results in the production of less radioactive liquid waste products.

Claims27

Dependent claims

An improved method for removing sludge and corrosion products from the interior of a heat exchanger vessel of the type wherein a liquid chemical cleaning agent is introduced into said vessel for a normal residence time of t minutes and then removed, and wherein said agent promotes corrosion within the interior of said heat exchanger vessel, wherein the improvement comprises the steps of:

generating a series of pressure pulses within the liquid agent after said agent has been introduced into the interior of said vessel to create shock waves in said liquid agent to dislodge, dissolve and fluidize said sludge and corrosion products, and
removing said liquid chemical cleaning agent after 10 to 67% of said normal residence time to substantially shorten the time required for the removal of the sludge and corrosion products from said vessel, and to reduce new corrosion from the chemical agent in said vessel by a factor which is greater than the percentage that the residence time is reduced.

An improved method for removing sludge and corrosion products from the interior of a heat exchanger vessel of the type having a tubesheet, heat exchanger tubes, support plates, and crevice regions between said tubes and said tubesheet and support plates, wherein said method involves the introduction of a liquid chelate-containing cleaning agent into the interior of the vessel for a residence time of t minutes to dissolve sludge and corrosion products from said crevice regions, and said liquid cleaning agent promotes corrosion within the interior of said heat exchanger vessel, wherein the improvement comprises the steps of:

generating a series of pressure pulses within the liquid agent after said agent has been introduced into the interior of said vessel to create shock waves in said liquid to dislodge, dissolve and fluidize said sludge and corrosion products in said crevice regions and other areas and to force a circulation of said agent through said crevice regions;
recirculating said liquid cleaning agent through a filter means to remove dislodged and fluidize sludge and corrosion products from said agent both to prevent said sludge and products from resettling back into the interior surface of said vessel and to maintain the strength of said agent, and
removing said liquid chemical cleaning agent after 10 to 46% of said normal residence time to substantially shorten the time required for the removal of the sludge and corrosion products from said vessel, and to reduce the new corrosion from the chemical agent in said vessel by a factor which is greater than the percentage that the residence time is reduced.

An improved method for removing sludge and corrosion products from the interior of the secondary side of a nuclear steam generator having a tubesheet, heat exchanger tubes, support plates, and crevice regions between said tubes and said tubesheet and support plates, wherein said method involves the serial introduction and removal from said secondary side of a plurality of chelate containing cleaning agents which promote corrosion within the interior of the steam generator, including an iron solvent for a residence time of between about 13-70 hours, and a copper solvent for a residence time of between about 6-24 hours, wherein the improvement comprises:

generating a series of pressure pulses within the liquid cleaning agent after each agent has been introduced into the secondary side, and
serially maintaining said iron solvent in said secondary side for a period of between about 6-16 hours, and said copper solvent rinse for a period of about 4 hours to substantially shorten the time required for the removal of the sludge and corrosion products from said secondary side and to reduce the new corrosion from the chemical agent in said secondary side by a factory which is greater than the percentage that the residence time is reduced.

Dependencies are inferred from the claim text.

Chemical cleaning method for steam generators utilizing pressure pulsing

Life of this patent

Chemical cleaning method for steam generators utilizing pressure pulsing

Life of this patent

Abstract

Claims27