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Renewing a national treasure: INL's Advanced Test Reactor undergoes sixth core overhaul
This article is available on the ANS website. The opening paragraphs are available; a free sign up is required to read the full text. The article is here: Renewing a national treasure: INL’s Advanced Test Reactor undergoes sixth core overhaul
Some text excerpts:
Out of the frenzy of nuclear technology and engineering development at the height of the Atomic Age, a few designs stand out above the rest—designs so innovative that they would not be surpassed for years, or even decades. An example of this unsurpassed design brilliance exists in the form of Idaho National Laboratory’s Advanced Test Reactor.
“ATR is really a beautiful machine,” said Sean O’Kelly, associate lab director for the ATR Complex. “The elegant cloverleaf core and control systems were a stroke of genius that solved just about every key problem of test reactor design. The designers’ solutions to those problems give us a testing capacity and flexibility that have yet to be matched.”
ATR’s distinctive cloverleaf core design, highlighted in the iconic photo of ATR in operation with the vivid blue glow of the Cherenkov effect, creates nine large flux traps in which experiments can be bombarded with a massive stream of neutrons from almost every direction. Combine this with its control cylinders that create an unchanging vertical flux profile for the entire height of the core and you have the highest capacity, highest power, and highest flexibility of any test reactor ever built. (Photo: INL)
Renewable by design
The ATR first powered up in 1967 and is still the world’s largest, most powerful, and highest-capacity materials test reactor. Even with these bragging rights, the ATR’s impact extends far beyond its design...
...Most of the ATR’s operating cycles last about 60 days. In between those cycles lie the “routine” outages that can last three to five weeks. Experiments are inserted or removed from the ATR’s test loops and other spaces during these outages. Every 12 to 24 months, the ATR undergoes a longer outage to allow for the repair or upgrade of other plant systems. Then, every 10 years on average, the ATR undergoes a major overhaul outage that lasts around nine months.
“For ATR, the beryllium reflector blocks and control cylinders that surround the core swell very gradually and develop cracks over time, due to our high neutron flux,” Vogel said. “We inspect and model this swelling very carefully, and it lets us know when it’s time to begin another core overhaul..."
...Many of the tools used to execute the core overhaul are one-off designs—some completely new, others modified to be more effective since they were last used in 2004. One example is a unique vacuum flow manifold that helped solve contamination control challenges from past CICs related to underwater handling of ATR’s hafnium components. Another is a new off-the-shelf, flexible shielding technology that helped reduce radiation dose while improving efficiency for those working with experiment in-pile tubes and other components.
Replacing the ATR’s key internal components also involves hundreds of pages of CIC-specific procedures, in addition to those used for routine refueling outages. Such rarely executed procedures all needed careful review and updating before the dismantling of the reactor could begin. The ATR’s document management team worked with operations, engineering, safety, radiological control, and other departments to bring each one up to current standards. This is even more difficult than it sounds when considering the state of computer technology and procedure management software during CICs in 2004 and 1994. This prep work has been important in ensuring the smooth execution of the core overhaul...
...The ATR can be viewed as the nation’s third-generation test reactor, inheriting a legacy of fuel and materials testing capability that began with the Materials Testing Reactor (1952–1970) and the Engineering Test Reactor (1957–1981). Each one brought major improvements in testing capability, and this legacy has been key to U.S. leadership in nuclear energy technology development. Even with planned upgrades, the ATR’s primary users recognize that the ATR in its current state cannot meet the current and growing demand for higher test throughput, larger volumes, and specific experimental conditions.
This recognition has prompted new discussions on the challenging task of sustaining thermal irradiation capabilities for several more decades. This could be done through recapitalization of the ATR or designing and constructing a new test reactor that could improve upon the ATR. Whatever the decision on how these capabilities will be sustained, it is clear that the demand for the ATR’s capabilities is greater than ever and that it won’t be replaced any time soon...
“ATR is really a beautiful machine,” said Sean O’Kelly, associate lab director for the ATR Complex. “The elegant cloverleaf core and control systems were a stroke of genius that solved just about every key problem of test reactor design. The designers’ solutions to those problems give us a testing capacity and flexibility that have yet to be matched.”
ATR’s distinctive cloverleaf core design, highlighted in the iconic photo of ATR in operation with the vivid blue glow of the Cherenkov effect, creates nine large flux traps in which experiments can be bombarded with a massive stream of neutrons from almost every direction. Combine this with its control cylinders that create an unchanging vertical flux profile for the entire height of the core and you have the highest capacity, highest power, and highest flexibility of any test reactor ever built. (Photo: INL)
Renewable by design
The ATR first powered up in 1967 and is still the world’s largest, most powerful, and highest-capacity materials test reactor. Even with these bragging rights, the ATR’s impact extends far beyond its design...
...Most of the ATR’s operating cycles last about 60 days. In between those cycles lie the “routine” outages that can last three to five weeks. Experiments are inserted or removed from the ATR’s test loops and other spaces during these outages. Every 12 to 24 months, the ATR undergoes a longer outage to allow for the repair or upgrade of other plant systems. Then, every 10 years on average, the ATR undergoes a major overhaul outage that lasts around nine months.
“For ATR, the beryllium reflector blocks and control cylinders that surround the core swell very gradually and develop cracks over time, due to our high neutron flux,” Vogel said. “We inspect and model this swelling very carefully, and it lets us know when it’s time to begin another core overhaul..."
...Many of the tools used to execute the core overhaul are one-off designs—some completely new, others modified to be more effective since they were last used in 2004. One example is a unique vacuum flow manifold that helped solve contamination control challenges from past CICs related to underwater handling of ATR’s hafnium components. Another is a new off-the-shelf, flexible shielding technology that helped reduce radiation dose while improving efficiency for those working with experiment in-pile tubes and other components.
Replacing the ATR’s key internal components also involves hundreds of pages of CIC-specific procedures, in addition to those used for routine refueling outages. Such rarely executed procedures all needed careful review and updating before the dismantling of the reactor could begin. The ATR’s document management team worked with operations, engineering, safety, radiological control, and other departments to bring each one up to current standards. This is even more difficult than it sounds when considering the state of computer technology and procedure management software during CICs in 2004 and 1994. This prep work has been important in ensuring the smooth execution of the core overhaul...
...The ATR can be viewed as the nation’s third-generation test reactor, inheriting a legacy of fuel and materials testing capability that began with the Materials Testing Reactor (1952–1970) and the Engineering Test Reactor (1957–1981). Each one brought major improvements in testing capability, and this legacy has been key to U.S. leadership in nuclear energy technology development. Even with planned upgrades, the ATR’s primary users recognize that the ATR in its current state cannot meet the current and growing demand for higher test throughput, larger volumes, and specific experimental conditions.
This recognition has prompted new discussions on the challenging task of sustaining thermal irradiation capabilities for several more decades. This could be done through recapitalization of the ATR or designing and constructing a new test reactor that could improve upon the ATR. Whatever the decision on how these capabilities will be sustained, it is clear that the demand for the ATR’s capabilities is greater than ever and that it won’t be replaced any time soon...
