Control Selection Techniques Employed for D&D Projects with Emphasis on Nuclear Criticality Safety Controls

Brenda L. HawksEngineering Director

Oak Ridge Office of Environmental ManagementJeff Castor

Criticality Safety Engineer, Navarro Research and Engineering

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Background Hazards during D&D are often different than hazards

present in an operating facility During D&D, a facility will, by definition, be undergoing

significant physical changes that often render engineered safety features ineffective and/or unreliableExample: safe geometry aspect of small diameter piping is lost

when piping is dismantled and collected together (in a waste box for disposal, or on a pallet on the ground, etc.)

D&D environment is dynamic. Tasks are typically non-routine, non-repetitive

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Background In developing an appropriate control set for D&D

activities, differences in the types of hazards and the effectiveness/reliability of engineered safety features must be considered

Risk can often be managed effectively via administrative controls in a D&D environmentExample: Rather than upgrade the sprinkler system in a facility

undergoing D&D, the fire hazard/risk can be managed by implementing a more robust combustible control program, fire watch requirements, etc. By doing so, D&D can continue to remove MAR and eliminate the hazard altogether, rather than waiting until the sprinkler system upgrades can be completed

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TRU Waste Processing Center (TWPC) Supports D&D of other facilities (e.g., K-25, other ETTP site

facilities) Waste containers (drums, boxes) received, repackaged and

characterized for transportation and disposal compliance NCS achieved by strict adherence to very low fissionable

mass levels In each individual container

In each repackaging area

Container/area fissionable mass controls selected as TSR controls

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TRU Waste Processing Center (TWPC) With very low fissionable masses, a “graded” NCS program

was approved by DOE Determined to be more cost effective (with no increase in

overall risk) to operate at very low fissionable masses than to develop a full-blown NCS program

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ORNL Facilities/Hot Cells D&D Facilities characterized and documented as low NCS

concern during static conditions (limited quantities of fissionable material, no activities conducted) under previous contractor with full NCS program

D&D to be performed by small contractor with no NCS staff

Tendency is to use ANSI standard subcritical mass limits and claim no NCS Program needed (i.e., entire facility inventory is less than the ANSI standard subcritical mass limit for the isotope of concern)

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ORNL Facilities/Hot Cells D&D However, there are differences during D&D activities as

compared to static facility conditions:Discovery of previously unknown quantities of fissionable

material are possibleEquipment with potential holdup collected together in waste

containers Also, ANSI standard subcritical limits are water based, and

are not always appropriate during D&D activitiesWill D&D involve organic cleaning of equipment/piping?Will waste containers be grouted to meet disposal requirements?

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ORNL Facilities/Hot Cells D&D Therefore, a minimal NCS Program is established, including

availability of a knowledgeable NCS engineer to identify and resolve potential concerns as D&D progressesNCS Program strongly credits facility inventory control program

(no addition of fissionable materials to facilities with exception of limited, small quantity sources) and anomaly detection program (to ensure NCS engineer involvement in discovery of previously unknown fissionable material items/materials)

Facility inventory control program and anomaly detection program both elevated as programmatic controls under the Hazardous Material Protection Program in the safety basis documents

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K-25 GDP D&D Operations involving significant quantities/forms of

fissionable material typically require certified Fissile Material Handlers per DOE O 426.2 (previously 5480.20A)

In a D&D environment, maintaining staff of certified Fissile Material Handlers is difficult due to type of work being conducted (dismantlement, deconstruction activities as opposed to material processing activities)

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Criticality Safety Officer (CSO) position/program provides enhanced NCS knowledge in the field.CSOs have a strong field presence with operations crews

CSOs knowledgeable of NCS requirements and controls

Good interface with both operations personnel and NCS engineers (who also have significant field presence)

CSO Program required as part of NCS Safety Management Program discussed in safety basis document, and in the DOE-approved NCS Program Description document

Training Implementation Matrix developed per DOE O 426.2 describes CSO position/program and provides qualification requirements

K-25 GDP D&D

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Conclusion

Risk can often be managed in a D&D environment utilizing a combination of administrative and programmatic controls in lieu of engineered controls, at reduced cost and with no increase in overall risk