Researchers run initial tests of singular complement for welding rarely irradiated steel alloys

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Scientists of a Department of Energy’s Light Water Reactor Sustainability Program (LWRS) and partners from the Electric Power Research Institute (EPRI) have conducted a initial coupling tests to correct rarely irradiated materials during DOE’s Oak Ridge National Laboratory.

ORNL and EPRI built an enclosed welding complement in a prohibited dungeon of ORNL’s Radiochemical Engineering Development Center. C. Scott White (ORNL) performs operations with remotely tranquil manipulators and cameras. The complement combines capabilities for laser welding and frictional stir welding of irradiated immaculate steels. Image credit: DOE LWRS; photographer Keith Leonard

The welding system, designed and commissioned in a prohibited dungeon during ORNL’s Radiochemical Engineering Development Center, safely encloses apparatus for laser and friction-stir welding. It will concede researchers to allege welding technologies for correct of irradiated materials by building estimate conditions and evaluating post-weld materials properties.

As chief energy plants age, materials that have been irradiated for several decades competence need correct or replacement. Advanced welding techniques will be indispensable during a extended operational lives of America’s chief energy plants; construction on many began in a 1970s. These plants beget approximately 20 percent of a nation’s electricity.


“Demonstration of modernized techniques for irradiated materials is a pivotal step in validating coupling correct as one slackening plan for fluctuating a life of components and shortening costs for a chief industry,” pronounced ORNL’s Keith Leonard, who leads investigate in a Materials Aging and Degradation Pathway for LWRS.

Mitigation strategies concentration on cost-effective repairs or replacements—either might need welding. During extended operation of reactors, helium is generated by a mutation of boron impurities by greeting with neutrons from a reactor core. Furthermore, nickel, a common alloying component in constructional alloys, will also beget helium, though by a slower two-step process. Helium era depends on a element and a plcae in a reactor, though for reactors surpassing 60 effective full-power years, helium era in core components can surpass 5 to 10 atomic collection per million—levels during that normal welding techniques can't be used to sufficient correct components.

Heat and highlight expostulate helium to fuse in immaculate steel, combining froth along bounds between “grains,” or micron-scale regions of order, that break a material. When steel is melted and resolidifies, differences in enlargement and contraction between a newly solidified element and surrounding element can build tensile stresses along a weakened, helium-bubble-containing pellet boundaries, inducing cracks. “That’s a biggest problem we face with welding irradiated materials,” Leonard said. The ORNL–EPRI complement uses modernized techniques that deliver reduction highlight than required welding, thereby shortening cracking.


On Nov. 17, a initial tests on irradiated element were achieved during ORNL with a laser weldingtechnique (see video below) that uses a primary laser to coupling and delegate beams to revoke tensile stresses circuitously a coupling section (a obvious focus has been submitted). The tests were conducted on samples, famous as “coupons,” of irradiated immaculate steel doped with 5, 10 and 20 collection of boron per million atoms. The materials were built into playing-card-sized coupons during ORNL and afterwards irradiated during a High Flux Isotope Reactor, a DOE Office of Science User Facility during ORNL. HFIR’s abundant, enterprising neutrons torpedo a coupons to change a boron into helium to copy a aging that would start in a blurb reactor after decades of deviation exposure.

Nov. 21 saw a first friction stir welding (see video below) of irradiated immaculate steel during ORNL. Unlike required arc welding, that employs fiery materials, attrition stir welding is a solid-state blending technique that uses a rotating apparatus to beget attrition and feverishness that softens materials though does not warp them. “At a little level, a atoms of any square of element get unequivocally close, and appealing army lift a atoms together to form one piece,” explained Zhili Feng, who leads ORNL’s Materials Joining Team.  Because attrition stir welding occurs next a melting point, it avoids enormous in correct welding of irradiated and helium-bearing materials. An synthetic neural network monitors attrition stir welding to detect conditions that can means coupling defects.

“Both correct welding technologies grown in a module are engineered to ‘proactively’ conduct a stresses during welding so they potentially offer solutions for correct [internal] reactor components with high helium levels—impossible with today’s welding correct technology,” Feng said. “As reactors continue to age (and helium continues to be generated), attention increasingly needs technologies to hoop high-helium-level scenarios.”

Preliminary observations showed both techniques constructed welds of good quality.

“The welding prohibited dungeon unequivocally determined ORNL as a core for building new techniques and new technologies for blurb chief energy generation,” Leonard said. In serve to lab imagination in welding and materials characterization, ORNL strengths embody different circuitously facilities, such as other prohibited cells and the Low Activation Materials Development and Analysis Laboratory to support post-weld materials characterization, and HFIR to beget exam element and serve age post-weld materials.

Next, a researchers will try welding materials with aloft helium calm and impersonate a irradiated materials after they’ve been welded, with techniques including microstructural investigate and automatic skill assessments. They will also re-age element in HFIR that has undergone a coupling correct to see how serve aging affects welds.

The LWRS Program conducts investigate and growth to raise a safe, fit and careful opening of a nation’s chief swift and extend handling lifetimes. EPRI, an independent, nonprofit organization, conducts investigate ancillary a safe, reliable, cost-effective and environmentally obliged use of chief energy as a era option. EPRI is building collection to muster a record to chief energy plants for on-site repairs. Once a corner obvious issues to ORNL and EPRI, companies could permit a record to make those on-site repairs.

“EPRI works broadly with researchers from companies and universities, and this case, a supervision lab, to residence hurdles in electricity, including reliability, efficiency, affordability, health, reserve and a environment,” pronounced Gregory Frederick, EPRI module manager. “We done a sincerely vast investment since we see a value for providing new believe that attention needs. No place has a vicious mass of imagination and comforts that Oak Ridge National Laboratory provides.”

Research and growth support for this plan came from a US Department of Energy Office of Nuclear Energy’s LWRS Program, EPRI’s Long Term Operations Program and ORNL. DOE and EPRI common costs for a development, design, fabrication, apparatus and contrast costs, and ORNL upheld installation-related costs. Industry can benefit entrance to this capability through DOE Office of Nuclear Energy appropriation opportunities or ORNL partnering mechanisms.

Source: ORNL


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