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An Extensive Engineering Design Resource for the Intermediate-Level Radioactive Waste
:: 09 July, 2008
Decommissioning of UKAEA Harwell, transforming it into a world-class centre for excellence in science and innovation, is a complex technical process requiring hard work in planning and implementation.
One of the companies supporting UKAEA in this work is Nuvia (formerly Nukem) Nuvia offers an extensive engineering design resource for the nuclear industry ranging from new build plant for radioactive and hazardous environments, shielded facilities and containment systems, and treatment plants for solid and liquid active waste in addition to extensive radiation safety and consulting expertise.
Nuvia has been awarded a contract to design and build a nuclear waste encapsulation facility at the site, which has included an Excel Automation conveyor system designed to transport stainless steel drums containing intermediate-level radioactive waste (ILW) through the process.
The drums, which are 800mm in diameter, 1200mm high and weigh up to 1000kg, are loaded onto the conveyor system from an existing drum storage facility.
The conveyor system then transports the drums through the process, which involves drum inspection followed by grout filling of the drums, before transporting them back to the existing storage facility.
During the process the weight of the drums increases to a maximum of 2000kg.
The Nuvia specification required the contact surface of the Excel conveyors to be stainless steel.
To meet this specification, Excel designed a bespoke handling system consisting of sets of powered roller conveyors fitted with stainless steel tube rollers and side guides; and cross-chain transfer units having stainless steel pads fixed to the chains.
The rectangular conveyor system layout carries drums inside a 'cell' with a concrete roof and walls.
As the drive motors are located outside the cell, each of the conveyors is fitted with a through-wall drive to enable the drive shaft and coupling of the motor gearbox to connect to the conveyor chains that drive the rollers.
The support structure of the conveyors and any equipment that is not in contact with the drums, are manufactured from carbon steel and finished with a special paint.
Because the cell is a restricted area Excel has also designed and supplied a drum removal system consisting of a hand operated cable winch recovery bogie and hydraulic cylinder-driven drum pushers.
In the event of a conveyor breakdown, the drum pushers are extended through the walls in order to push drums into a position where they can be transferred to the existing storage facility.
Proving all components and the system itself off-site was also a key requirement of the contract.
This involved Excel testing a sample of the conveyor drive system to ensure that the lubricant free drive chains used 'incell' were fit for purpose and could be approved.
The system was then made and assembled in Worcester and laid out in the company workshops.
Each item of equipment underwent a unit trial, which was then followed by a total factory acceptance test and buy-off by both Nuvia and its customer UKAEA.
The whole system was then stripped down, packed, itemised, and delivered to site, where it was installed by Nuvia.
Commenting for Nuvia, design manager Andy Blue says: "Excel Automation was involved in the project from the start, and the input of its design and engineering team on the conveying system was invaluable.
The installation itself also went very smoothly and we were delighted with the result".
About Radioactive Wastes
Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. They are sometimes the products of nuclear processes, such as nuclear fission. However, industries not directly connected to the nuclear industry can produce large quantities of radioactive waste. It has been estimated, for instance, that the past 20 years the oil-producing endeavors of the United States have accumulated eight million tons of radioactive wastes. The majority of radioactive waste is "low-level waste", meaning it contains low levels of radioactivity per mass or volume. This type of waste often consists of used protective clothing, which is only slightly contaminated but still dangerous in case of radioactive contamination of a human body through ingestion, inhalation, absorption, or injection. In the United States alone, the Department of Energy states that there are "millions of gallons of radioactive waste" as well as "thousands of tons of spent nuclear fuel and material" and also "huge quantities of contaminated soil and water". Despite these copious quantities of waste, the DOE has a goal of cleaning all presently contaminated sites successfully by 2025. The Fernald, Ohio site for example had "31 million pounds of uranium product", "2.5 billion pounds of waste", "2.75 million cubic yards of contaminated soil and debris", and a "223 acre portion of the underlying Great Miami Aquifer had uranium levels above drinking standards". The United States currently has at least 108 sites it currently designates as areas that are contaminated and unusable, sometimes many thousands of acres The DOE wishes to try and clean or mitigate many or all by 2025, however the task can be difficult and it acknowledges that some will never be completely remediated, and just in one of these 108 larger designations, Oak Ridge National Laboratory, there were for example at least "167 known contaminant release sites" in one of the three subdivisions of the 37,000-acre (150 kmē) site. Some of the U.S. sites were smaller in nature, however, and cleanup issues were simpler to address, and the DOE has successfully completed cleanup, or at least closure, of several sites.
The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced when trying to establish a long term energy production plan, yet there was hope it could be safely solved. A recent research report on the Nuclear Industry perspective of the current state of scientific knowledge in predicting the extent that waste would find its way from the deep burial facility - back to soil and drinking water (such that it presents a direct threat to the health of human beings - as well as to other forms of life) is presented in a document from the IAEA (The International Atomic Energy Agency) - which was published in October 2007 This document states "The capacity to model all the effects involved in the dissolution of the waste form, in conditions similar to the disposal site, is the final goal of all the research undertaken by many research groups over many years. As we will see in this report, this kind of investigation is far from being finished". In the United States, the DOE acknowledges much progress in addressing the waste problems of the industry, and successful remediation of some contaminated sites, yet also major uncertainties and sometimes complications and setbacks in handling the issue properly, cost effectively, and in the projected time frame.
UKAEA is has the proven experience and innovative thinking to deliver safe and efficient clean-up services for our customers as well as developing fusion as a clean and sustainable energy source for the future. See more about our organisation.
The civil nuclear programme ended with the closure of the Prototype Fast Reactor at Dounreay in 1994. UKAEA had already turned its attention to a new task - that of restoring the environment of its sites as reactors finished operating. Since then we have made extensive progress, and in 2005 we safely dismantled our fifteenth reactor - ZEBRA - at Winfrith.
In April 2005 the Nuclear Decommissioning Authority (NDA) was formed to take responsibility for the UK's civil nuclear clean-up programme. UKAEA is now a contractor to the NDA for management of decommissioning at Dounreay, Harwell, Windscale, Winfrith and the JET facilities at Culham. Also in 2005, the Government approved UKAEA's plans to expand and compete for wider business.
UKAEA's tradition of leading edge research continues at Culham, where fusion scientists from around the globe are developing fusion as a new energy source. The JET facility opened in 1983 and has set world records for plasma performance.