Decontamination and Decommissioning Experience cont'd

DOE-STD-1128-98

Discussions of D&D activities at several DOE plutonium facilities are provided by

Adkisson (1987), Bond et al. (1987), and King (1980), as well as by Shoemaker and Graves

(1980), Garner and Davis (1975), Wynveen et al. (1982), Hunt et al. (1990), Freas and

Madia (1982), and Garde et al. (1982a, 1982b). They describe D&D activities that took

place in several types of plutonium facilities, including fabrication facilities, research and

development laboratories, and a storage facility. Plutonium-contaminated glove boxes,

hoods, ventilation ductwork, laboratory equipment, structural components (i.e., walls and

floors), and filter banks were decontaminated. Typically, decontamination methods

included wiping with a damp cloth or mop, using strippable coatings, mechanical spalling

of concrete floor surfaces, and fixating contamination on a piece of equipment (e.g., a

hood), followed by disassembling the item inside a contamination control enclosure.

Some lessons learned from past studies include the following:

-- Waste management planning should begin early in the D&D planning stages and

consider the following:

The possibility exists that there may be more stringent regulations for shipping

hazardous or radioactive wastes than disposing of it and

Compliance with all applicable waste management requirements may be difficult

(e.g., the Waste Isolation Pilot Project (WIPP) does not accept mixed wastes or

TRU waste that contains plastics or foams).

-- It is difficult to decontaminate some items with inaccessible surfaces to less than the

TRU limit (100 nCi/g) so that they can be disposed of as LLW. In some situations, it

may be possible to decontaminate to <100 nCi/g of TRU, but the decontamination

process may generate a large volume of liquid waste or be time-consuming enough to

prohibit its use.

-- Temporary enclosures are effective in controlling contamination when reducing the

size of large equipment such as glove boxes. Any loose contamination on the

equipment should be fixed before placing it in the enclosure.

-- Criticality safety issues regarding the geometry of any waste material containing fissile

material need to be considered.

Adkisson (1987) reported on the decommissioning of a plutonium fuel fabrication plant at

the Sequoyah Fuels Corporation's Cimarron Facility, located in north-central Oklahoma.

Process equipment, glove boxes, tanks, piping, and ventilation ducts required

decontamination. Controlling personnel exposures, maintaining containment of radioactive

material during the dismantling of contaminated items, and reducing the volume of TRU

material were the primary considerations during the decommissioning activities. A large

modified glove box provided containment for dismantling and cutting up the various

equipment using a plasma-arc unit. A passive, gamma-ray nondestructive assay technique

(heavily shielded NaI detector with collimator) was used to measure the plutonium content

of cut-up pieces. Finally, the loaded waste drums were measured using a waste drum

counter to ensure that plutonium levels were less than 100 nCi/g.

10-11