(489f) Modeling of Pluggage and Spatial Distribution of Particulate Matter Deposited in the Savannah River Site H-Canyon Process Vessel Vent Filters

A model has been developed to predict the rate of pluggage and spatial distribution of fissile particulate material in the Savannah River Site H-Canyon Process Vessel Vent (PVV) filters. The PVV filters are multilayer fiberglass mat filters in the off-gas vents from H-Canyon. Exhaust fans pull H-Canyon air through these filters, which are located upstream from the final sand filter and the exhaust stack. The PVV filters periodically become plugged with ammonium nitrate generated by the PUREX process in H-Canyon. When pluggage occurs, the vent flow is shut down, and the PVV filter are flushed. Fissile material that accumulates in these filters between flushes poses a nuclear criticality risk. A study was requested to evaluate the feasibility of extending the interval between flushes and the possibility of raising the criticality safety limit.

A transient model for flow through and ammonium nitrate deposition in the PVV filters was developed. The particle deposition rate in this model was based on the Torgeson correlation. The model predicted loading transients and pluggage intervals that generally agreed with historic loading and flushing records. Notably, regarding criticality concerns, the model predicted that no more than 4% of any material, including fissile material, accumulates in any one location on the filters. Accordingly, it was recommended that the geometric distribution of material be considered in future criticality analyses.