Processing Nuclear Materials

Interview conducted by G.P. ThomasFeb 12 2014

Peter Witting, Ph.D., Senior Process Technology Engineer at Harper International, talks about how Harper is involved in the processing of nuclear materials and what this entails.

Could you please give a brief overview of how Harper International is involved in the nuclear materials sector?

Harper offers a range of advancements in energy efficiency, maintenance, temperature uniformity and safety control, whilst also offering reliable systems for fuel processing. Within the nuclear fuel processing sector, important applications include:

• Oxidation of UO2 pellets, swarf, and powder t to U3O8
• Denitration of Uranyl nitrate and hydrofluorination of UO2
• Sintering UO2 pellets for reactor fuel rods
• Waste remediation

Harper supplies uranium dioxide(UO2) nuclear fuel sintering furnaces for Pressurized Heavy Water Reactor’s [PHWR] and Pressurized Water Reactors [PWR]. In addition to the sintering furnaces, Harper produces oxidation furnace systems to convert UO2 to U3O8. Two other Nuclear processes Harper has worked in are the reduction furnaces for conversion of UO3 to UO2 with H2 and hydrofluorination of UO2 with HF to produce UF4.

What are the main thermal processing solutions that Harper International provides?

Harper provides pusher systems for the nuclear fuel sintering processes. These sintering furnaces provide the high temperature capability required along with hydrogen atmosphere and dewpoint control. The Harper sintering furnaces are highly reliable and have remarkable longevity. There are Harper nuclear sintering furnaces that have been in operation for more than 25 years. These sintering furnace systems typically are molybdenum element heated with high alumina oxide based refractory.

Rotary systems are used in several nuclear fuel applications that Harper works in. The rotary systems are used in the oxidation, reduction, and hydrofluorination processes implemented in the nuclear fuel production lines. These rotaries require tight atmosphere seals to contain the potentially flammable atmosphere, as well as dust containment measures.

Many of these systems Harper provides are fully integrated for different process steps. These may include a cascading rotary system where each rotary delivers a different process step. The integrated cascading rotaries deliver an effective tool for producing nuclear fuel.

Harper has also provided unique systems including mechanically fluidized bed furnace systems. These highly engineered systems deliver distinctive processing capabilities, catered for the specific nuclear fuel application.

How long has Harper been involved in nuclear materials processing? How has this involvement evolved over time?

John Harper and his colleagues invented the first furnace to process nuclear fuels in the 1940’s. In 1957 we produced our first nuclear fuel sintering furnace for General Electric. Harper has become the world’s leading provider of customized systems for reacting and sintering nuclear fuels. These early systems were smaller sized sintering pusher furnaces.

As the process has matured, the systems have become higher capacity, with customized features to address process requirements. Initially the systems Harper provided were singular systems for specific process requirements. This has extended into providing integrated systems which combine several process steps. Harper has also branched out into other areas of nuclear processing including remediation, reduction and hydrofluorination as well as other processes.

Could you explain the process involved in sintering nuclear fuels?

Nuclear fuel sintering often is a two-step process. The first step involves removal of the binder. This debindering step typically is at a significantly lower temperature than the sintering step. The sintering step requires hydrogen atmosphere – often with dewpoint control, and process temperatures of 1600 to 1800°C.

What are the typical applications of these sintering processes?

The typical fuels produced from Harper sintering furnace system include nuclear fuel for PWR, PHWR and CANDU reactors.

Could you explain in a bit more detail how you are involved in waste remediation?

During nuclear fuel pellet production there are several operations which produce waste. These include the swarf from pellet centreless grinding operations to meet the high tolerances required for nuclear fuel and broken pellets from different steps in the operation. These swarf or waste products are oxidized in Harper oxidation system from UO2 to U3O8. This material is then re-introduced into the production of nuclear fuel.

Harper systems have also been used to dilute highly enriched nuclear material into non-enriched material. U-235 is fissile – can sustain a fission chain reaction. Some Harper systems have been used to convert highly enriched UO2 to U3O8. This enriched U3O8 is blended with natural grade U3O8 material to dilute the concentration of U-235. This dilute material is then reprocessed into nuclear fuel.

What can Harper offer in terms of energy efficiency?

Harper's design practice provides for robust, efficient designs. For nuclear fuel processing, reliability is of utmost importance. Harper provides energy efficient systems with well proven insulation packages catered to the process and furnace requirements.

Harper’s rotary system includes baffles and other features to reduce end tube radiation loss to improve the energy efficiency. Rotary systems often provide great energy efficient value since there is no carrier load which requires energy to heat and cool the boat or product tray.

Could you outline the Ignite™ Program in more detail?

Through this project Harper offers support to emerging industries, from the early stages of research and development, with the aim of assisting these customers in turning the next generation of material innovations into profitable new markets.

Using the depth and breadth of experience in thermal processing at Harper, we try to ensure success as they scale up their process operations by partnering closely with our customer.

Could you outline a recent nuclear case study that Harper has recently been involved in?

Harper has recently been involved in a cascading rotary system where two different process steps are applied in an integrated series of rotaries. Each rotary require a different atmosphere and both require tight atmosphere controls and seal.

The system integration requires consideration of atmosphere separation and control as well as safety controlling the nuclear fuel material being processed. For this work a detailed package including P&ID’s, atmosphere schematics, layout design was completed prior to detailed engineering design. These basic engineering documents drove the project to a successful conclusion.

What does the future hold for nuclear materials processing? How will Harper be a part of this?

The demand for electric power continues to increase placing a strain on the supply. This demand results in continued growth in the demand for nuclear power. Nuclear power is one of the cleanest energy sources and worldwide expansion is anticipated.

Many existing plants are coming up for refurbishment. Harper is focusing on these refurbishments to extend the life and safety of existing production equipment. The changing requirements of these plants often require upgrades and modifications of the production facilities. Many weapons grade nuclear materials are planned for reprocessing. These sensitive materials require special attention and requirements.

Harper will continue to build upon its base technology in this field to meet the challenges of this growing market. We will devise turnkey solutions with our range of offerings including gas treatment and handling and fully integrated control systems.

About Peter Witting

Peter Witting, Ph.D., Senior Process Technology Engineer at Harper International, received a Ph.D., M.S., and B.S. in Mechanical Engineering from the University at Buffalo.  Peter came to Harper in the year 2000, after working for five years at Naval Undersea Warfare Center.

In his current role, Dr. Witting oversees technical aspects of process and equipment development to support production of high value added materials. Some of the materials include: tungsten carbide, molybdenum, cobalt, carbon nanotubes, high surface area carbon, boron nitride, silicon and other solar materials, etc. Dr. Witting’s work is published worldwide and he has three U.S patents, including a unique design for a High Temperature Reactor.