Oxide Dissolution Example Assessment

DOE-HDBK-3010-94

7.0 Application Examples; Dissolving Operations Examples

The dissolution vessel holds only 23 l of solution. In the larger glovebox

accountability slab tank, sufficient nitric acid has been added for cooling and dilution

that 125 l of solution are present. If the criticality is postulated to occur in the

dissolver, the 23 l versus 100 l discrepancy can be ignored for the sake of simplicity.

The DR assigned for the plutonium in solution is 1.0. If the criticality were assumed

to occur in the accountability tank, a DR of 0.8 (100/125) can be used due to the

100 l evaporation basis assumed. Keeping in mind that the purpose of the release

model is not to derive the "absolute" answer, it is fitting, at least initially, to use a DR

of 1.0 and accept the result as conservative. If a double batching of plutonium is

arbitrarily considered the source of the criticality, the respirable airborne release is:

(1322*2) g * 1.0 * 5E-4 * 1.0 = 1.3 g

As in the previous powder criticality example, the exact value obtained is of little

relevance to criticality safety management.

7.3.2.3

Oxide Dissolution Example Assessment

The release estimates associated with the oxide dissolution line are comparable to those

associated with the feed preparation line (subsection 7.3.1.3), with the maximum estimate of

2.6 g for boiling dissolver solution being twice the expected bound for feed preparation.

Using the most conservative meteorological assumptions, potential consequences at the site

boundary are below 5 rem, and below 1 rem if deposition is accounted for.

Actual operational insight generated by the numbers is again small compared to the total

operational considerations for the oxide dissolution line described. The vessels and piping

need to be capable of withstanding temperatures and acid concentrations associated with the

process, but no release estimate was needed to make that realization. Such a simple,

informal verification would be a matter of course in any hazard analysis. The main insight

potentially attainable is, again, a new insight only if thought was not previously focused on

types of stresses causing release. It is that the dissolver heating cycle can significantly

contaminate vessel vent piping and tanks due to a single failure (e.g, temperature indication

low, steam flow valve sticks). Even though this process upset condition is not expected to

directly produce an occupational exposure, it is worth preventing at some level of cost to

minimize future decontamination and decommissioning difficulties. Accordingly, while the

issue does not need high level attention, such as safety-class or safety-significant structure,

system, or component designation, it is a desirable goal for the design and operation of the

process to be aware of the issue and, to a reasonable degree, minimize the chance of the

event and of a failure to detect it.

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