Example 9: Mitigating the Effects of an Earthquake

DOE-STD-1120-2005/Vol. 2

involved in the activity were trained (i.e., procedure review and pre-job briefing) on these safety control

requirements.

Example 11:

Mitigating the Effects of an Earthquake

A plutonium facility scheduled to be decommissioned within the next 10 years was to be analyzed for the

effects and consequences of earthquakes. As part of the integrated hazard analysis, a seismic assessment

revealed a potential for structural failure of the building during a credible seismic event. The facility was

in long-term S&M, awaiting deactivation, and contained a large inventory of releasable radioactive

material in its processing cells. The hazard analysis indicated that with more than two cell cover blocks

removed the consequences of the seismic event would be unacceptable. The facility walkdown indicated

that six cells were found without cover blocks in place.

Rather than instituting facility structural upgrades or modifying the facility to prevent or mitigate the

additional release of material that could occur with numerous cover blocks out of place, a simple, cost-

effective, solution involved reinstalling the cell cover blocks on these six cells. This action allowed for

the facility to remain within its analyzed safety envelope. Once the cover blocks were reinstalled, a

specific administrative control was established in the TSR that prohibited their removal during activities

authorized within the DSA... This simple and practical approach avoided the potentially large costs

associated with seismically upgrading the equipment and/or facility to address the discovered

vulnerability.

This approach promoted: (1) modifying operations (i.e., no cover blocks off at any time) and (2)

enhancing confinement integrity (i.e., reinstalling cover blocks), instead of requiring the facility to be

structurally upgraded to meet the seismic requirements.

Example 12:

Applying Hold Points in TSRs During Decommissioning

A Hazard Category 2 plutonium processing facility had been retired for more than 30 years and was being

prepared for final decommissioning. The facility process systems had been flushed and deactivated to its

current inventory of about 2 kg of Pu-239, much of which was determined to be held up in process

systems (i.e., approximately 1.5 kg was contained within six small process vessels). The potential existed

for significant uncertainty in total inventory, due to the inability to assay structure, systems, or

components (e.g., the pipe trench) beyond the pipes and vessels immediately accessible.

The existing TSRs for inventory and criticality control were designed to be applied to facility modes of

operation. Imbedded within the TSRs were several "hold" points that facilitated additional assays or

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