#Convair NB-36H

[historyofguns]

The article discusses the Convair NB-36H, a nuclear-powered bomber developed during the Cold War by the United States Air Force and the Atomic Energy Commission. Post-World War II, nuclear power was seen as a miracle energy source, leading to its consideration for military applications beyond submarines and supercarriers, like bombers. The NB-36H was a modified Convair B-36 Peacemaker, equipped with an air-cooled nuclear reactor, although the reactor never powered the aircraft in flight. Despite extensive research, including 47 test flights, the program was deemed too costly and risky, ultimately scrapped, as missile advancements reduced the need for such bombers. This endeavor reflects Cold War era technological ambitions and challenges in nuclear propulsion development.

[usafphantom2]

Convair NB-36H experimental aircraft that carried nuclear reactor. It was nicknamed "The Crusader".created for the Aircraft Nuclear Propulsion program, or the ANP, to show the feasibility of a nuclear-powered bomber.Its development ended with the cancellation of ANP program.

@CcibChris via X

[dronescapesvideos]

Convair NB-36H Experimental Atomic Bomber with a Boeing B-50 Superfortress, 1955. * Video: B-52 STRATOFORTRESS And The History Of U.S. Giant Bombers: From WWII To The Cold War Link:

https://youtu.be/RLptzCz-87Q

[jcmarchi]

Nuclear Power Renaissance with Molten Salts - Technology Org

New Post has been published on https://thedigitalinsider.com/nuclear-power-renaissance-with-molten-salts-technology-org/

Nuclear Power Renaissance with Molten Salts - Technology Org

A science team is reinventing nuclear energy systems via molten salt technologies.

A retro wonder gleaming white in the sun, propelled by six rear-facing rotors and four jet engines affixed to the longest wings ever produced for a combat aircraft, the Convair B-36 Peacemaker looks like it flew right out of a 1950s science fiction magazine.

Frozen uranium containing fuel salt (NaF-BeF2-UF4), inside a glovebox in Raluca Scarlat’s SALT lab. Illustration by Sasha Kennedy/UC Berkeley

One of these bombers, which flew over the American Southwest from 1955 to 1957, was unique. It bore the fan-like symbol for ionizing radiation on its tail. The NB-36H prototype was designed to be powered by a molten salt nuclear reactor — a lightweight alternative to a water-cooled reactor.

Nuclear-propelled aircraft like the NB-36H were intended to fly for weeks or months without stopping, landing only when the crew ran short of food and supplies. So what happened? Why weren’t the skies filled with these fantastical aircraft?

“The problem was that nuclear-powered airplanes are absolutely crazy,” says Per F. Peterson, the William S. Floyd and Jean McCallum Floyd Chair in Nuclear Engineering. “The program was canceled, but the large thermal power to low-weight ratio in molten salt reactors is the reason that they remain interesting today.”

Because of numerous concerns, including possible radioactive contamination in the event of a crash, the idea of nuclear-powered aircraft never took off. But nuclear submarines, using water as coolant, completely replaced their combustion-powered predecessors. Civilian reactors were built on the success of submarine systems, and as a result, most nuclear reactors today are cooled with water.

Professor Per Peterson holds a single fuel pebble, which can produce enough electricity to power a Tesla Model 3 for 44,000 miles. Illustration by Adam Lau / Berkeley Engineering

While most water-cooled reactors can safely and reliably generate carbon-free electricity for decades, they do present numerous challenges in terms of upfront cost and efficiency.

Molten salt reactors, like those first designed for nuclear-powered aircraft, address many of the inherent challenges with water-cooled reactors. The high-temperature reaction of such reactors could potentially generate much more energy than water-cooled reactors, hastening efforts to phase out fossil fuels.

Now, at the Department of Nuclear Engineering, multiple researchers, including Peterson, are working to revisit and reinvent molten salt technologies, paving the way for advanced nuclear energy systems that are safer, more efficient and cost-effective — and may be a key for realizing a carbon-free future.

Smaller, safer reactors

In the basement of Etcheverry Hall, there’s a two-inch-thick steel door that looks like it might belong on a bank vault. These days, the door is mostly left open, but for two decades it was the portal between the university and the Berkeley Research Reactor, used mainly for training. In 1966, the reactor first achieved a steady-state of nuclear fission.

Fission occurs when the nucleus of an atom absorbs a neutron and breaks apart, transforming itself into lighter elements. Radioactive elements like uranium naturally release neutrons, and a nuclear reactor harnesses that process.

Concentrated radioactive elements interact with neutrons, splitting themselves apart, shooting more neutrons around and splitting more atoms. This self-sustaining chain reaction releases immense amounts of energy in the form of radiation and heat. The heat is transferred to water that propels steam turbines that generate electricity.

The reactor in Etcheverry Hall is long gone, but the gymnasium-sized room now houses experiments designed to test cooling and control systems for molten salt reactors. Peterson demonstrated one of these experiments in August. The Compact Integral Effects Test (CIET) is a 30-foot-tall steel tower packed with twisting pipes.

The apparatus uses heat transfer oil to model the circulation of molten salt coolant between a reactor core and its heat exchange system. CIET is contributing extensively to the development of passive safety systems for nuclear reactors.

After a fission reaction is shut down, such systems allow for the removal of residual heat caused by radioactive decay of fission products without any electrical power — one of the main safety features of molten salt reactors.

The first molten salt reactor tested at Oak Ridge National Laboratory in the 1950s was small enough to fit in an airplane, and the new designs being developed today are not much larger.

Conventional water-cooled reactors are comparatively immense — the energy-generating portion of the Diablo Canyon Power Plant in San Luis Obispo County occupies approximately 12 acres, and containment of feedwater is not the only reason why.

The core temperature in this type of reactor is usually kept at some 300 degrees Celsius, which requires 140 atmospheres of pressure to keep the water liquid. This need to pressurize the coolant means that the reactor must be built with robust, thick-walled materials, increasing both size and cost. Molten salts don’t require pressurization because they boil at much higher temperatures.

In conventional reactors, water coolant can boil away in an accident, potentially causing the nuclear fuel to meltdown and damage the reactor. Because the boiling point of molten salts are higher than the operational temperature of the reactor, meltdowns are extremely unlikely.

Even in the event of an accident, the molten salt would continue to remove heat without any need for electrical power to cycle the coolant — a requirement in conventional reactors.

“Molten salts, because they can’t boil away, are intrinsically appealing, which is why they’re emerging as one of the most important technologies in the field of nuclear energy,” says Peterson.

The big prize: efficiency

Assistant professor Raluca Scarlat uses a glovebox in her Etcheverry Hall lab. Illustration by Adam Lau / Berkeley Engineering

To fully grasp the potential benefits of molten salts, one has to visit the labs of the SALT Research Group. Raluca O. Scarlat, assistant professor of nuclear engineering, is the principal investigator for the group’s many molten salt studies.

Scarlat’s lab is filled with transparent gloveboxes filled with argon gas. Inside these gloveboxes, Scarlat works with many types of molten salts, including FLiBe, a mixture of beryllium and lithium fluoride. Her team aims to understand exactly how this variety of salt might be altered by exposure to a nuclear reactor core.

On the same day that Peterson demonstrated the CIET test, researchers in the SALT lab were investigating how much tritium (a byproduct of fission) beryllium fluoride could absorb.

Salts are ionic compounds, meaning that they contain elements that have lost electrons and other elements that have gained electrons, resulting in a substance that carries no net electric charge. Ionic compounds are very complex and very stable. They can absorb a large range of radioactive elements.

This changes considerations around nuclear waste, especially if the radioactive fuel is dissolved into the molten salt. Waste products could be electrochemically separated from the molten salts, reducing waste volumes and conditioning the waste for geologic disposal.

Waste might not even be the proper term for some of these byproducts, as many are useful for other applications — like tritium, which is a fuel for fusion reactors.

Salts can also absorb a lot of heat. FLiBe remains liquid between approximately 460 degrees and 1460 degrees Celsius. The higher operating temperature of molten salt coolant means more steam generation and more electricity, greatly increasing the efficiency of the reactor, and for Scarlat, efficiency is the big prize.

“If we filled the Campanile with coal and burned it to create electricity, a corresponding volume of uranium fuel would be the size of a tennis ball,” says Scarlat. “Having hope that we can decarbonize and decrease some of the geopolitical issues that come from fossil fuel exploration is very exciting.”

“Finding good compromises”

Thermal efficiency refers to the amount of useful energy produced by a system as compared with the heat put into it. A combustion engine achieves about 20% thermal efficiency. A conventional water-cooled nuclear reactor generally achieves about 32%.

According to Massimiliano Fratoni, Xenel Distinguished Associate Professor in the Department of Nuclear Engineering, a high-temperature, molten salt reactor might achieve 45% thermal efficiency.

So, with all the potential benefits of molten salt reactors, why weren’t they widely adopted years ago? According to Peter Hosemann, Professor and Ernest S. Kuh Chair in Engineering, there’s a significant challenge inherent in molten salt reactors: identifying materials that can withstand contact with the salt.

Anyone who’s driven regularly in a region with icy roads has probably seen trucks and cars with ragged holes eaten in the metal around the wheel wells. Salt spread on roads to melt ice is highly corrosive to metal. A small amount of moisture in the salt coolant of a nuclear reactor could cause similar corrosion, and when combined with extreme heat and high radiation, getting the salt’s chemistry right is even more critical.

Hosemann, a materials scientist, uses electron microscopes to magnify metal samples by about a million times. The samples have been corroded and or irradiated, and Hosemann studies how such damage alters their structures and properties. These experiments may help reactor designers estimate how much corrosion to expect every year in a molten salt reactor housing.

Hosemann says molten salt reactors present special engineering challenges because the salt coolant freezes well above room-temperatures, meaning that repairs must either be done at high temperatures, or the coolant must first be drained.

Commercially successful molten salt reactors then will have to be very reliable, and that won’t be simple. For example, molten salt reactors with liquid fuel may be appealing in terms of waste management, but they also add impurities into the salt that make it more corrosive.

Liquid fuel designs will need to be more robust to counter corrosion, resulting in higher costs, and the radioactive coolant presents further maintenance challenges.

Nuclear engineering graduate students Sasha Kennedy and Nathanael Gardner, from left, work with molten salt. Illustration by Adam Lau/Berkeley Engineering

“Good engineering is always a process of finding good compromises. Even the molten salt reactor, as beautiful as it is, has to make compromises,” says Hosemann.

Peterson thinks the compromise is in making molten salt reactors modular. He was the principal investigator on the Department of Energy-funded Integrated Research Project that conducted molten salt reactor experiments from 2012 to 2018.

His research was spun off into Kairos Power, which he co-founded with Berkeley Engineering alums Edward Blandford (Ph.D.’10 NE) and Mike Laufer (Ph.D.’13 NE), and where Peterson serves as Chief Nuclear Officer.

The U.S. Nuclear Regulatory Commission just completed a review of Kairos Power’s application for a demonstration reactor, Hermes, as a proof of concept. Peterson says that high-temperature parts of Kairos Power’s reactors would likely last for 15 to 25 years before they’d need to be replaced, and because the replacement parts will be lighter than those of conventional reactors, they’ll consume fewer resources.

“As soon as you’re forced to make these high-temperature components replaceable, you’re systematically able to improve them. You’re building improvements, replacing the old parts and testing the new ones, iteratively getting better and better,” says Peterson.

Lowering energy costs

California is committed to reaching net zero carbon emissions by 2045. It’s tempting to assume that this goal can be reached with renewables alone, but electricity demand doesn’t follow peak energy generating times for renewables. 

Natural gas power surges in the evenings as renewable energy wanes. Even optimistic studies on swift renewable energy adoption in California still assume that some 10% of energy requirements won’t be achieved with renewables and storage alone.

Considering the increasing risks to infrastructure in California from wildfires and intensifying storms, it’s likely that non-renewable energy sources will still be needed to meet the state’s energy needs.

Engineers in the Department of Nuclear Engineering expect that nuclear reactors will make more sense than natural gas for future non-renewable energy needs because they produce carbon-free energy at a lower cost. In 2022, the price of natural gas in the United States fluctuated from around $2 to $9 per million BTUs.

Peterson notes that energy from nuclear fuel currently costs about 50 cents per million BTUs. If new reactors can be designed with high intrinsic safety and lower construction and operating costs, nuclear energy might be even more affordable.

Molten salt sits on a microscope stage in professor Raluca Scarlat’s lab. Illustration by Adam Lau/Berkeley Engineering

Even if molten salt reactors do not end up replacing natural gas, Hosemann says the research will still prove valuable. He points to other large-scale scientific and engineering endeavors like fusion reactors, which in 60 years of development have never been used commercially but have led to other breakthroughs.

“Do I think we’ll have fusion-generated power in our homes in the next five years? Absolutely not. But it’s still valuable because it drives development of superconductors, plasmas and our understanding of materials in extreme environments, which today get used in MRI systems and semiconductor manufacturing,” says Hosemann. “Who knows what we’ll find as we study molten salt reactors?”

Source: UC Berkeley

You can offer your link to a page which is relevant to the topic of this post.

[stone-cold-groove]

Bad idea - great execution. The nuclear-powered Convair NB-36H Crusader.

[tpmmpt-1]

NB-36H Peacemaker experimental aircraft and B-50 Superfortress chase plane during research and development taking place at the Convair plant at Forth Worth, Texas

[photoyage]

Convair NB-36H in flight. (U.S. Air Force photo)

[neverwasmag]

In 1946, the United States Air Force began to study the feasibility of nuclear-powered aircraft. Only one plane, built by Convair, was ever tested. The problem, as Steve Weintz puts it in The National Interest, was that leaders “couldn’t figure out how to pay for it or why they needed it.”

Convair B-36 Peacemaker

Cutaway of a Convair B-36 Peacemaker strategic bomber from Popular Mechanics, April 1954

Convair B-36 Peacemaker strategic bomber in flight (USAF)

Two Convair B-36 Peacemaker strategic bombers, 1955 (USAF)

The Convair B-36 Peacemaker had been designed as a long-range bomber to be able to reach Nazi Germany from America and fly back.

It was arguably obsolete from the start. The B-36 was piston-powered at a time when the Germans were pioneering jet technology.

However, the Peacemaker, which was about twice the size of the Boeing B-29 Superfortress, was the only aircraft America had in the late 1940s that was both big enough to carry the hydrogen bomb and long-range enough to reach Russia.

Convair modified two B-36s, designed NB-36Hs, to carry air-cooled nuclear reactors in their bombing bays. Shields were installed in the middle of the aircraft to protect the pilots from radiation. The cockpit was further encased in lead and rubber.

None of the reactors was ever used to power the aircraft. Test flights were carried out to investigate the effect of radiation on aircraft systems, nothing more.

North American XB-70 Valkyrie

North American XB-70 Valkyrie strategic bomber in flight (NASA)

A North American XB-70 Valkyrie strategic bomber is escorted by fighter jets over California, June 8, 1966 (USAF)

The XB-70 Valkyrie was originally conceived as a nuclear-powered bomber before North American Aviation put a jet engine in it.

Cruising at Mach 3+, the Valkyrie was thought to be immune to interceptor aircraft, which were the only effective weapon against bombers at the time.

But when the Soviets unveiled surface-to-air missiles in the late 1950s, it called the XB-70’s invulnerability into question. The advent of intercontinental ballistic missiles later that decade also made manned bomber aircraft less relevant. The Air Force eventually canceled the plane in 1961.

Interchangeable nuclear reactors

Popular Mechanics (April 1957)

Northrop design for a nuclear-powered bomber, from Popular Mechanics, April 1957

Popular Mechanics reported in April 1957 that Lee A. Ohlinger, a radiation expert and the head of the computer center at Northrop Aircraft, proposed powering aircraft with interchangeable nuclear reactors.

The crew would have piloted the aircraft from a detachable cockpit in the tail assembly that could fly away in case of emergency. The people on the ground from such an emergency would have been less fortunate, which may be why Ohlinger’s suggestion was never studied seriously.

Cold War America seriously considered powering aircraft with nuclear reactors In 1946, the United States Air Force began to study the feasibility of nuclear-powered aircraft. Only one plane, built by Convair, was ever tested.

[nebris]

An air-to-air view of the Convair NB-36H Peacemaker experimental aircraft (s/n 51-5712) and a Boeing B-50 Superfortress chase plane during research and development taking place at the Convair plant at Forth Worth, Texas (USA). The NB-36H was originally a B-36H-20-CF damaged at Carswell Air Force Base, also at Forth Worth, by a tornado on 1 September 1952. This plane was called the Nuclear Test Aircraft (NTA) and was redesignated XB-36H, then NB-36H, and was modified to carry a three megawatt, air-cooled nuclear reactor in its bomb bay. The reactor, named the Aircraft Shield Test Reactor (ASTR), was operational but did not power the plane. The NTA completed 47 test flights and 215 hours of flight time (during 89 of which the reactor was operated) between July 1955 and March 1957 over New Mexico and Texas. This was the only known airborne reactor experiment by the USA with an operational nuclear reactor on board. The NB-36H was scrapped at Fort Worth in September 1958 when the Nuclear Aircraft Program was abandoned. 

https://en.wikipedia.org/wiki/Convair_NB-36H

[historyofguns]

The article discusses the development and testing of the Convair NB-36H, a nuclear-powered bomber pursued by the United States Air Force in the post-World War II era. Motivated by a fascination with nuclear power's potential, the Air Force aimed to create aircraft with unlimited range by integrating nuclear technology. Initiated by the Manhattan Project's successor, the program evolved into the Aircraft Nuclear Propulsion (ANP) Program. Despite extensive efforts and resources invested, totaling over $7 billion by 1961, the program faced significant technical and practical challenges. The NB-36H, modified from a B-36 Peacemaker bomber and designed to test nuclear propulsion feasibility, completed numerous test flights without the reactor powering the aircraft, before being scrapped when the program was terminated under President Kennedy's administration. The article underscores the project's ambitious vision and practical shortcomings, while also noting that parallel studies on nuclear propulsion were considered by the U.S. Navy and the Soviet Union, none of which proceeded to operational implementation.

[usafphantom2]

Convair NB-36H Experimental Atomic Bomber with a Boeing B-50 Superfortress, 1955.

@dronescapesvideos via X

[stone-cold-groove]

Bad idea - great execution. The nuclear-powered Convair NB-36H Crusader.

[usafphantom2]

Ronnie Bell Following

Convair NB-36H

Convair NB-36H in flight. Note the radiation warning symbol on the tail. (U.S. Air Force photo)The NB-36H (originally designated XB-36H) was used in the studies and testing of an airborne nuclear reactor. The reactor to be carried aloft was not to be used for aircraft propulsion but primarily for determining many unknown factors pertaining to the effects of nuclear reaction. The NB-36H, named "The Crusader," flew 47 times during the mid-1950s.

Project MX-1589 was carried under two Air Force contracts -- one pertaining to research and development of an airframe and one for the construction of what became the Nuclear Aircraft Research Facility operated by Convair-Fort Worth for the Air Force.

The project was classified until late 1955 when the Department of Defense revealed the existence of the B-36 testbed for an airborne atomic reactor. The nose section of the aircraft had to be completely redesigned and resulted in one of the first uses of a full-scale working mock-up. The nose section mock-up included a hydraulic design feature providing simulation of aircraft take-off position, and detail design of the crew compartment interior duplicating actual aircraft conditions of ventilation, color scheming and other crew comfort and safety factors never before involved in airframe construction.

The XB-36H carried a crew of five: pilot, copilot, flight engineer, and two nuclear engineers. All crew members were located in the forward section of the aircraft while the atomic reactor was located aft. The greenhouse nose of a production B-36H was replaced by a more conventional cockpit arrangement. The new nose section was slightly shorter than the original and the nose landing gear was moved six inches forward to allow for a crew entrance/escape hatch just behind the nose landing gear.

On Labor Day (Sept. 1) 1952, Carswell Air Force Base was struck by a tornado and several aircraft were damaged. These aircraft were returned to Convair for major repairs. In the group was airplane No. 242 (S/N 51-5712), which had lost the nose section of the fuselage. Convair proposed that this airplane be used for the nuclear program, with the damaged nose section forward of Station 5 to be replaced with the nose section and crew compartment then being designed as a mock-up. The proposal was agreed to by the Air Force.

The size of the crew compartment was determined by the total allowable weight of the nose section of a B-36H airplane. In order to lessen the indoctrination, which would otherwise be necessary, the pilot and co-pilot stations were held as closely as possible to the arrangement of the standard B-36. The nuclear engineer stations were designed to incorporate the necessary instrumentation for the reactor operation. Engine scanning normally performed by crew members from the rear of the conventional B-36, had to be taken over by television cameras in the test aircraft. The placement of the television set presented another problem. The set had to be located where the flight engineer could readily see it. Although space was not available at the flight engineer's station, there was room in the overhead area between the nuclear engineers' stations within easy viewing distance of the flight engineer.

The color treatment and lighting arrangement of the interior surfaces were designed to help eliminate as much eye fatigue as possible. A gray color scheme used in the nuclear and flight engineers' compartments, proved unfavorable for the pilot and co-pilot stations. Exterior light passing through the yellow windshield turned the light gray into an unfavorable color. By using lavender, in the pilot and co-pilot compartment, and illusion of gray is achieved.

Type Number built/

converted Remarks

NB-36H 1 (cv) Airborne testbed for a nuclear reactor

TECHNICAL NOTES:

Armament: None

Engines: Six Pratt & Whitney R-4360-53 radials of 3,800 hp each (takeoff power) and four General Electric J47-GE-19 turbojets of 5,200 lbs. thrust each

Maximum speed: Approx. 420 mph at 47,000 ft.

Cruising speed: 235 mph

Service ceiling: Approx. 47,000 ft.

Span: 230 ft. 0 in.

Length: 162 ft. 1 in. (as B-36H, the NB-36H was slightly shorter)

Height: 46 ft. 8 in.

Weight: 357,500 lbs. (maximum gross weight)

Crew: Five (pilot, copilot, flight engineer and two nuclear engineers)

Serial number: 51-5712 (originally B-36H-20-CF)

Via Flickr

[usafphantom2]

Convair NB-36H Peacemaker experimental aircraft (s/n 51-5712) fitted with a nuclear reactor and a Boeing B-50 Superfortress chase plane

[usafphantom2]

Convair NB-36H in flight. Note the radiation warning symbol on the tail. (Photo Source: USAF)

[usafphantom2]

Ronnie Bell Following

Convair NB-36H

NB-36H nuclear reactor testbed producing contrails in flight.

Via Flickr