Methods for operating and methods for reducing post-shutdown radiation levels of nuclear reactors

A method for reducing post-shutdown radiation levels of a nuclear reactor, the method comprising:

• injecting first and second chemicals together to water in the reactor prior to reactor shutdown;
• wherein the first and second chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein the first chemical comprises hydrogen,
• wherein the second chemical comprises platinum, and
• wherein the platinum has a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion.

A method for reducing post-shutdown radiation levels of a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• wherein the two or more chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein a first chemical of the two or more chemicals comprises hydrogen,
• wherein a second chemical of the two or more chemicals comprises platinum, and
• wherein the platinum has a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion.

A method for reducing post-shutdown radiation levels of a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• wherein the two or more chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein a first chemical of the two or more chemicals comprises hydrogen,
• wherein a second chemical of the two or more chemicals comprises platinum, platinum ions, or platinum and platinum ions, and
• wherein the platinum has a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion, the platinum ions have a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion, or the platinum and platinum ions have a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion.

A method for reducing post-shutdown radiation levels of a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• wherein the two or more chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein a first chemical of the two or more chemicals comprises hydrogen,
• wherein a second chemical of the two or more chemicals comprises one or more metal compounds, and
• wherein the one or more metal compounds comprise one or more of aluminum, cerium, chromium, gold, hafnium, indium, iridium, iron, manganese, molybdenum, nickel, niobium, osmium, palladium, platinum, potassium, rhodium, ruthenium, sodium, tantalum, terbium, tin, titanium, tungsten, vanadium, yttrium, and zirconium.

A method for operating a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• and
• conducting the reactor shutdown;
• wherein the two or more chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein a first chemical of the two or more chemicals comprises a reducing agent,
• wherein a second chemical of the two or more chemicals comprises platinum, and
• wherein the platinum has a concentration in the reactor water that is greater than or equal to about 1 part per trillion and less than or equal to about 75 parts per trillion.

A method for operating a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• and
• conducting the reactor shutdown;
• wherein the first and second chemicals trigger release of one or more radioactive soluble impurities from at least one out-of-core surface of the reactor into the reactor water,
• wherein the first chemical comprises hydrogen,
• wherein the second chemical comprises one or more metal compounds, and
• wherein the one or more metal compounds comprise one or more of aluminum, cerium, chromium, gold, hafnium, indium, iridium, iron, manganese, molybdenum, nickel, niobium, osmium, palladium, platinum, potassium, rhodium, ruthenium, sodium, tantalum, terbium, tin, titanium, tungsten, vanadium, yttrium, and zirconium.

A method for mitigating stress-corrosion cracking in a nuclear reactor, the method comprising:

• injecting two or more chemicals together to water in the reactor prior to reactor shutdown;
• wherein a first chemical of the two or more chemicals comprises hydrogen,
• wherein a second chemical of the two or more chemicals comprises one or more metal compounds,
• wherein the one or more metal compounds comprise one or more of aluminum, cerium, chromium, gold, hafnium, indium, iridium, iron, manganese, molybdenum, nickel, niobium, osmium, palladium, platinum, potassium, rhodium, ruthenium, sodium, tantalum, terbium, tin, titanium, tungsten, vanadium, yttrium, and zirconium, and
• wherein at least one of the one or more metal compounds provides a catalytic effect for the hydrogen to scavenge oxidants from the reactor water.