NOREM
Encyclopedia
NOREM is a hardfacing
material developed by Electric Power Research Institute
(EPRI) to deal with radio safety issues associated with the use of cobalt
alloys in nuclear power station coolant systems (see stellite
for a discussion of the problem). It is a solid-solution strengthened
austenitic matrix with a continuous network of eutectic and non-eutectic carbides at the grain
boundaries. It is intended to be deposited by various welding
processes.
These are extremely hard alloys. NOREM 02 is ten times as resistant as 308 stainless steel to cavitation erosion. They are essentially corrosion
-immune under the conditions inside CANDU reactor
s and erode at about 200 micrograms per square centimetre per year under pressurized water reactor
conditions. Due to the high hardness, the strength is relatively low: approximately 120 ksi yield strength and it fails at 0.6% elongation.
's Indian Point
unit 2. It is now used in about 800 valves installed by about 30 utility companies. There has been one case of a NOREM valve disc being found damaged, at the Callaway Nuclear Generating Station
, though it seems the valve was not being used in an appropriate application.
Given the high cavitation resistance, NOREM has been tested for hydroelectric applications; it seems not to be as impressively cavitation-resistant in the field as in the lab, though only one layer of the material was used in the test, and EPRI recommends at least two.
Hardfacing
Hardfacing is a metalworking process where harder or tougher material is applied to a base metal. It is welded to the base material, and generally takes the form of specialized electrodes for arc welding or filler rod for oxyacetylene and TIG welding...
material developed by Electric Power Research Institute
Electric Power Research Institute
The Electric Power Research Institute conducts research on issues related to the electric power industry in USA. EPRI is a nonprofit organization funded by the electric utility industry. EPRI is primarily a US based organization, receives international participation...
(EPRI) to deal with radio safety issues associated with the use of cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
alloys in nuclear power station coolant systems (see stellite
Stellite
Stellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon...
for a discussion of the problem). It is a solid-solution strengthened
Solid solution strengthening
Solid solution strengthening is a type of alloying that can be used to improve the strength of a pure metal. The technique works by adding atoms of one element to the crystalline lattice of another element . The alloying element diffuses into the matrix, forming a solid solution...
austenitic matrix with a continuous network of eutectic and non-eutectic carbides at the grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...
boundaries. It is intended to be deposited by various welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
processes.
Characteristics
There are eight variants of NOREM currently available, depending on application and designated 02, 02A, 03A, 03B, 04A, 04B, 05A, 05B. A typical elemental composition is 60% iron, 25% chromium, 4.5% manganese, 4.0% nickel, 3.3% silicon, 2.0% molybdenum, 1.2% carbon. Earlier compositions included either significantly more manganese (12% in alloy 04) or significantly more nickel (8% in alloy M2).These are extremely hard alloys. NOREM 02 is ten times as resistant as 308 stainless steel to cavitation erosion. They are essentially corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
-immune under the conditions inside CANDU reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...
s and erode at about 200 micrograms per square centimetre per year under pressurized water reactor
Pressurized water reactor
Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...
conditions. Due to the high hardness, the strength is relatively low: approximately 120 ksi yield strength and it fails at 0.6% elongation.
Use in power plants
The first use of NOREM was as replacement discs in three Chemical Volume Control System isolation valves at Consolidated EdisonConsolidated Edison
Consolidated Edison, Inc. is one of the largest investor-owned energy companies in the United States, with approximately $14 billion in annual revenues and $36 billion in assets...
's Indian Point
Indian Point Energy Center
Indian Point Energy Center is a three-unit nuclear power plant station located in Buchanan, New York just south of Peekskill. It sits on the east bank of the Hudson River, 38 miles north of New York City...
unit 2. It is now used in about 800 valves installed by about 30 utility companies. There has been one case of a NOREM valve disc being found damaged, at the Callaway Nuclear Generating Station
Callaway Nuclear Generating Station
The Callaway Plant is a nuclear power plant located on a 5,228-acre site in Callaway County, Missouri, near Fulton, Missouri. It began operating on December 19, 1984. The plant, which is the state's only commercial nuclear unit, has one 1,190-megawatt Westinghouse four-loop pressurized water...
, though it seems the valve was not being used in an appropriate application.
Given the high cavitation resistance, NOREM has been tested for hydroelectric applications; it seems not to be as impressively cavitation-resistant in the field as in the lab, though only one layer of the material was used in the test, and EPRI recommends at least two.