Go big or go small?

Above: Reducing the volume and repacking components bound for disposal can be an efficient choice (Source: NAC LPT)

THE NUCLEAR ENERGY INSTITUTE AND industry leaders in December 2015 laid out a multi-year strategy in their “Delivering the Nuclear Promise” initiative to ensure the nuclear industry’s competitive viability. Plant licensees have since focused on efficiency and the economics of plant operations, but owners must also address the options for minimising the cost of handling and processing large components. Due to the competitive nature of radioactive waste disposal sites, it is currently often less expensive for operators to dispose of a component directly it is to use techniques to reduce the volume of the component, release it and or repackage it.

Options such as one-time use, soft-sided IP-1 packaging have dramatically reduced disposal costs, as have recent changes to disposal sites’ waste acceptance criteria. Nonetheless, processing large components remains a viable option. It too can significantly lower costs if done properly and in the right circumstances.

A variety of factors can determine whether to pursue processing, either for volume reduction or for direct disposal. These include: the overall costs associated with handling and transportation; volumetric disposal pricing; the total void-space of the component; and the amount of volume reduction that can be achieved.

In the past, when evaluating whether to employ this type of work for processing or direct disposal, I would use a formula to determine what route to take – I call it the “Rule of 50.” Depending upon the waste stream, it is not universally applicable, but statistically, it works well.

Applying the rule

Transportation is a key consideration in determining whether to pursue volume reduction or shipment for direct disposal. Often transporting a large component represents a sizeable portion of the total cost for processing or disposal. Using rail to transport a large component can significantly reduce the cost, but it does not reduce the price of disposal. The first step in deciding whether a component should be processed is to ask this question: “Is there a processing facility capable of handling the component within 50 per cent of the distance of the disposal site?” If transport to the processing facility is roughly along the same path as the disposal site, volume reduction and repackaging of component pieces may be a feasible approach.

If the component can be down-sized and packaged into Department of Transportation (DOT) standard dimensional disposal packaging (such as B-12s, B-25s, intermodals, sea- land containers or IP-1 bags), it can then be shipped on a standard flat-bed vehicle. This eliminates additional costs associated with over-height or over-weight shipments and the costs of large component handling at the disposal site. In addition, the closer the processor is to the shipment’s point of origin, the lower are permitted or escorted transport costs.

If there is a processing facility capable of handing the component within a reasonable distance, the processing option merits consideration. For the sake of this exercise, processing is defined as: reducing volume through mechanical means (plasma-arc cutters, oxy-acetylene torches, magnesium rod cutting, reciprocating saws, grinding wheels, etc.); releasing processed portions of the component for unrestricted use; and repackaging and disposal of any residual wastes that remain or were generated in the process.

If there is a processor within reasonable distance, and it has the capabilities and facilities to handle the component, the next step is determining the entire cost of processing. If the processor can segment and repackage the component into road-ready disposal packaging for 50 percent or less of the cost of direct disposal (not including efforts for release for unrestricted use or beneficial reuse), processing may be a cost-saving solution.

Volumetric disposal pricing and void space restrictions at disposal facilities often require that void spaces be grouted or otherwise stabilised prior to disposal, to reduce the risk of further settling of material in the disposal cell.

If the component’s void space is 50 percent or more of the total volume and it is possible, through processing and repackaging, to reduce the overall disposal volume by at least 50 percent, processing becomes a real option. Examples of components that fall into this category are moisture separator reheaters, feedwater heaters, heat exchangers, pressure vessels, large tanks, etc. I have found that labour and materials costs associated with processing, releasing, and repackaging large components are nearly equal to the current direct disposal costs. So if the overall waste volume of the component cannot be reduced by 50 percent at less than 50 percent of the cost of direct disposal, processing is probably not economic.

Above: Sometimes shipping a whole component, such as this feedwater heater, makes more economic sense (Source: NAC LPT)

It the answer to the three ‘Rule of 50’ questions above is yes, it suggests that volume reduction and processing for disposal should be assessed. If the answer to any of the above is no, direct disposal often will be the more cost- effective option.

Other considerations

Lead-encased objects such as large lead-shielded tanks or shipping containers, or obsolete or damaged casks are ideal candidates for processing prior to disposal, because they tend to be over-weight and the lead is easy to recover. If the lead can be segregated from the other constituent materials and decontaminated for release, either for unrestricted use or for beneficial reuse, the remaining the component materials may no longer require handling and disposal as mixed waste, significantly reducing further transportation and disposal costs.

Another consideration is waste class and characterisation. If a constituent of the component’s waste class is greater than class A, it is more likely to be a candidate for volume reduction and repackaging rather than direct disposal, because of the different disposal costs for class B and C LLRW materials. Shipping and packaging requirements are obviously more robust (Type A and Type B packaging), and ALARA must be considered to determine if processing is feasible. If time, shielding, and distance can be employed to manage worker dose responsibly, then volume reduction and repackaging of components can significantly reduce overall disposal costs. Once the component has been processed, materials can be segregated according to waste classification, potentially reducing the material that would otherwise be classified as class B or C waste. Once the segregated material is in packaging suitable for disposal, it can be classified prior to final shipment.

For many years, I worked for a processing facility that processed large components. The facility’s location was a key benefit to the plants that it served, along with the personnel’s talent, experience, and processing knowledge.

When making an evaluation on whether to bid a job as direct disposal or to develop and propose a large component processing plan, we used a quick check of the ‘Rule of 50’ for distance, cost and volume, together with a quick evaluation on waste-stream segregation. With this approach, we could determine whether to expend further resources to pursue the work, or simply load it on a truck in a soft-sided IP-1 bag and ship it directly to disposal.

Author: Michael Brisbin Miller, Director of business development at NAC LPT LLC