Spill of Process Materials in an SCB

The spill of process materials in an SCB is an anticipated operational eyent. Spills may range from minor seepage or leaks of small quantities of materials to a complete spill of the process contents due to operator error or due to failure of process containers. Process container... 

Section 3.3.2.3.5, Accident Selection, identified one beyond DBA as, Multiple simultaneous errors or events that affect multiple SCBs, resulting in release of the contents of multiple targets. Release of the fission products from multiple targets (six) in a single SCB has already been analyzed in two DBAs Spill of Process Materials in an SCB and Fire in a Process SCB. The source term and consequences of the Multiple simultaneous errors or events... beyond DBA are discussed in Section 3.4.3.1 and S.4.3.2 below. Two additional hazards are discussed in Sections 3.4.3.3 and 3.4.3.4 as beyond DBAs to provide a perspective of the residual risk associated with the operation of the facility. These beyond DBAs are 1) seismic events resulting in a release of radiological material and 2) dispersal of radiological material by an explosion in the HCF. 

The spill of process materials in an SCB is an anticipated operational event Spills may range from minor seepage or leaks of small quantities of materials to a complete spill of the process contents due to operator error or due to failure of process containers. Process container failures may occur either due to spontaneous mechanical failures and/or may be induced by operator actions. Provisions for accommodating such spills have been incorporated in process equipment design in the fomn of spill trays, absorbent material, and SCB washdown systems. Clean up of the spilled material and returning the SCB to a clean operational state will be an operational Inconvenience, but will be a routine task. 

Potential doses at the exclusion area boundary (3000 m) have been evaluated using the methodology described in Section 3.4.1. These techniques have been used to calculate the potential dose consequences resulting from the released source term for this DBA, which are 110% of the process spill scenario, or a maximum of 2 rem. The probability of a fire in an SCB, however, has been assessed in Appendix 3E.3 to be three or more orders of magnitude lower than spill events (Appendix 3E.2), and fires which could result in release of radioactive materials are even less likely. 

Of the various scenarios evaluated, the most serious consequences resulted from the spill of volatile process materials or a fire in an SCB. Based on these evaluations, structures, systems and components with the potential to mitigate this hazard were identified. While many features in the HCF control or mitigate the hazards for both workers and the public, the most significant mitigative feature for the protection of the public is the filtered HCF exhaust ventilation system. 

While fire protection systems are typically considered important to safety, fire protection In the HCF does not provide a major contribution to defense in depth due to the limited quantity of flammable materials permitted in the process extraction SCB s and the form and containerization of the hazardous process materials. A fire in an SCB does not threaten the ventilation system filters and would normally not result in any significant release of hazardous materials. The fire scenario has been evaluated and included in the accident analyses described in Section 3.4, which indicates that the release is bounded by the consequences of a process spill in the SCB. 

It is expected that under normal operational conditions, the airborne concentration level In the Zone 2A canyon would be well below the derived air concentration (DAC) limits (2E-8 ci/m3 for 1-131 from 10 CFR 835). This assessment is based on normal handling and containerization of process materials and the fact that the Zone 2A canyon volume is continually circulated by the ventilation system. However, contamination above these levels may exist in the canyon on a transient basis. An accident condition, such as simultaneous process spill and SCB failure, could hypothetically release a target s volatile contents, or 100% of the iodine inventory directly to the canyon. These theoretical contamination levels can also serve as a basis for evaluation of the potential consequences of ventilation failure. 

The chemicals in syringes are transported to the SCBs in kits of materials and equipment The chemical hazard from acid and base corrosive chemicals wiQ be mitigated by remote handling in the SCBs and by the sealed process hardware and glassware. -Any spills are contained in a spill tray and cleaned up with an acid spill kit in the SCB. 

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