Radiological inventory

The radiological inventory (specific activity and radionuclide composition). 

This radiological inventory is made by on site measurements, calculation and estimation of residual activity by the mean of computing code, sampling and radiochemical analyses in order to verify the computational results. 

The potential source term for each of the selected DBAs was conservatively derived based on the maximum potential radiological inventory and assuming that the entire inventory was available for release (i.e. the airborne release fraction was assumed to be 1.0). 

In the event of SCB failure, the structures comprising the boundary of the Zone 2A canyon provide a secondary confinement barrier to the release of radioactive materials to the HCF and to the environment. This is a major contributor to defense in depth in that, in abnormal or accident conditions where the SCB boundary has been degraded, an independent and redundant confinement capability exists to mitigate the release of radiological materials. The process of filtration of this airflow is similar to that for Zone 1, however only one stage of charcoal filtration is provided in the MER, based on the expectation that radiological inventories in the Zone 2A canyon will be significantly less than those in Zone 1, except under accident conditions. 

The accident analyses in this SAR will be developed based on the conservative assumption that the entire radiological inventory associated with the number of isotope targets expected to be simultaneously at risk is available in a form which is readily transported, i.e. an ARF of 1.0 will be assumed for all materials. This assumption will apply to the inventory contained in targets which are simultaneously in-process". In-process" is defined as that time during which chemical process operations are being conducted on the material subject to release, up to the point of solidification of process residuals. Once process residuals are solidified, the fission products are In a much less volatile state (see waste accident scenario analysis described in Section 3.4.2.4) and the inventory can essentially be considered to be not at risk. 

Normally, all of the above possible radiological inventories at process stations would be contained by the process SCB, they wouid be drawn into the ventilation system, and trapped on ventilation system filters. If the SCB failed, or a pre-existing failure were undetected, the radiological inventory could be released directly into the Zone 2A canyon. 

An evaluation of the levels of expected and potential airborne contamination levels can be based on source term characterization analyses conducted for other DBA s such as the process spill evaluation. Normally, less than 1% of a target s iodine inventory is expected to be released to the SCB during processing. Under abnormal conditions, up to 100% of the iodine inventory may be released to the SCB. These values can be used as conservative upper bound limits on the potential iodine concentration in the SCB. The radiological inventories used in this analysis are based on the inventory of a maximally irradiated target. 

The dose consequence from a HC2 quantity inventory is calculated by applying the ratio of X/Q at 300 m to that at 3000-m with the meteorology used in the MACCS2 calculations for the dose versus distance database and applying this ratio to the value of 1 Rem at 300 m. The resulting dose will represent a conservative upper bound on the public dose since the maximum radiological inventory corresponding to HC2 levels was used in the analysis. 

The material in-process inventory is that of a maximally irradiated target. During the one hour initial processing period, the entire radiological inventory is potentially available for release. Once the iodine has been collected in the iodine trap, it would not be vulnerable to DBE effects. Thus, for the remainder of the processing period only the residual process liquid, containing about 75% of the total fission product inventory and totaling about 14,000 curies, is available as a potential source term. This source term is present until the waste is solidified (approximately 3 hours). 

An evaluation of the response of the HCF in a Design Basis Earthquake (DBE) has been accomplished in Appendix 3E, and likelihoods of occurrence have been assessed for the configuration of confinement systems and availability of radiological inventory for reiease. 

The Room 108 and Room 109 shield doors are normally In the up position to provide shielding from the significant radiological inventory that will exist in Room 109. Shield door 3A will be lowered for the (remote) placement of radioactive waste into Room 109 for storage. Shield door 2A will be lowered for the (remote) removal of radioactive waste from Room 109. Thus, the safety functions applicable to the shield door controls are ... 

Based on the radiological inventory of isotope targets described in Chapter 3, the consequences at the exclusion boundary for the following filter configurations have been calculated ... 

During the one-hour initial processing period, the entire radiological inventory is potentially available for release. Once the iodine has been collected in the iodine trap, it would not be... 

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