Enclosed Filter Media

DOE-HDBK-3010-94

5.0 Surface Contamination; HEPA Filters

In another study, five plenum-sized filters were tapped and crushed and a total of 349 g of

particulate materials collected. The total weight of the filters was 90,900 g and the material

generated represents 0.384%. Under the assumption that the media mass is 5% of the filter

weight, the particles collected represent 7.68% of the media mass. The fraction 10 m and

less was 9.261 wt/o of the total collected and 0.71 wt/o of the filter media mass.

Two different glovebox-sized filters were also studied in this effort and the same test

conditions. A total of 9 g was collected with a total filter weight of 41.4 kg. The particles

collected represent 0.022 wt/o of the total filter mass and, under the assumptions used

previously, 0.43 wt/o of the filter media mass. The size distribution of the particles

generated was not characterized but in all other studies reported was <10% (in most cases

much less). Under the assumption the 10 m fraction is 10%, the particles generated

represent 0.043 wt/o of the media mass.

The data reproduced in Table A.55 are from a study where plenum-sized filters from a

variety of plena were wrapped in plastic and projected 3-ft repeatedly onto an unyielding

concrete floor. Table 5-6 presents relevant data from Table A.55 taken from the referenced

document. For the fraction 10 m in diameter and less generated based upon the assumed

total media mass, the bound is 5E-3 with a median of 2E-3 and an average of 2E-3. This is

consistent with the results above that indicate releases of particles 10 m in diameter and less

ranging from 1E-5 to 7E-3.

5.4.4.1

E n closed F ilter M ed ia

Filter media is generally contained within multiple enclosures. The filter housings

themselves are enclosures, and in-use filters are contained in plenum enclosures that are

substantially more robust than the plastic wrap holding filters in the data cited. Used filters

are generally held in plastic wrapping inside waste drums. Even severe shock-impact for

these configurations is no worse than the mechanical crushing performed on the filters

examined. It is assumed that the fraction of particles 10 m diameter and less released from

the double-wrapped HEPA filters that were crushed bounds the release from enclosed HEPA

filter media subjected to crush-impact stresses that compromise the enclosure.

For the first test with 30 filters, the total mass of particulate obtained <25 m LLD was

5E-5 as a fraction of overall media weight. In the second crushing experiment with an

additional 30 filters, the fraction <10 m was estimated to be 1E-5. The majority of this

material would not be expected to be filtered radioactive material. However, due to the great

uncertainties associated with the test results, an additional order of magnitude increase is

imposed resulting in bounding ARF and RF values of 5E-4 and 1.0 for this stress.

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