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Title: Radiological and toxicological analyses of tank 241-AY-102 and tank 241-C-106 ventilation systems

Abstract

The high heat content solids contained in Tank 241-C-106 are to be removed and transferred to Tank 241-AY-102 by sluicing operations, to be authorized under project W320. While sluicing operations are underway, the state of these tanks will be transformed from unagitated to agitated. This means that the partition fraction which describes the aerosol content of the head space will increase from IE-10 to IE-8 (see WHC-SD-WM-CN062, Rev. 2 for discussion of partition fractions). The head spare will become much more loaded with suspended material. Furthermore, the nature of this suspended material can change significantly: sluicing could bring up radioactive solids which normally would lay under many meters of liquid supernate. It is assumed that the headspace and filter aerosols in Tank 241-AY-102 are a 90/10 liquid/solid split. It is further assumed that the sluicing line, the headspace in Tank 241-C-106, and the filters on Tank 241-C-106 contain aerosols which are a 67/33 liquid/solid split. The bases of these assumptions are discussed in Section 3.0. These waste compositions (referred to as mitigated compositions) were used in Attachments 1 through 4 to calculate survey meter exposure rates per liter of inventory in the various system components. Three accident scenarios are evaluated:more » a high temperature event which melts or burns the HEPA filters and causes releases from other system components; an overpressure event which crushes and blows out the HEPA filters and causes releases from other system components; and an unfiltered release of tank headspace air. The initiating event for the high temperature release is a fire caused by a heater malfunction inside the exhaust dust or a fire outside the duct. The initiating event for the overpressure event could be a steam bump which over pressurizes the tank and leads to a blowout of the HEPA filters in the ventilation system. The catastrophic destruction of the HEPA filters would release a fraction of the accumulated filter loadings and would lead to an unfiltered pathway from the radioactively contaminated and toxic aerosols in the head space (vapor space) of the tank into the outside environment. The initiator for the unfiltered (continuous) release scenario is wetting of the HEPA filters with an accompanying filter breach or failure of the seals surrounding the filter in the enclosure. No releases from the filters themselves are assumed in this scenario. In the absence of controls, the exhaust system would continue to expel the contaminated head space air into the outside environment in all three of these scenarios.« less

Authors:
Publication Date:
Research Org.:
Fluor Daniel Hanford Inc., Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Environmental Restoration and Waste Management, Washington, DC (United States); USDOE Assistant Secretary for Nuclear Energy, Washington, DC (United States)
OSTI Identifier:
10148994
Report Number(s):
HNF-SD-WM-CN-099-Rev.1
ON: DE99050912; BR: EW3130010; TRN: AHC29927%%269
DOE Contract Number:
AC06-96RL13200
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 11 Aug 1998
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; HANFORD RESERVATION; RADIOACTIVE WASTE STORAGE; STORAGE FACILITIES; VENTILATION SYSTEMS; RADIATION MONITORING; CHEMICAL ANALYSIS; EVALUATION; 052002; WASTE DISPOSAL AND STORAGE

Citation Formats

Himes, D.A.. Radiological and toxicological analyses of tank 241-AY-102 and tank 241-C-106 ventilation systems. United States: N. p., 1998. Web. doi:10.2172/10148994.
Himes, D.A.. Radiological and toxicological analyses of tank 241-AY-102 and tank 241-C-106 ventilation systems. United States. doi:10.2172/10148994.
Himes, D.A.. Tue . "Radiological and toxicological analyses of tank 241-AY-102 and tank 241-C-106 ventilation systems". United States. doi:10.2172/10148994. https://www.osti.gov/servlets/purl/10148994.
@article{osti_10148994,
title = {Radiological and toxicological analyses of tank 241-AY-102 and tank 241-C-106 ventilation systems},
author = {Himes, D.A.},
abstractNote = {The high heat content solids contained in Tank 241-C-106 are to be removed and transferred to Tank 241-AY-102 by sluicing operations, to be authorized under project W320. While sluicing operations are underway, the state of these tanks will be transformed from unagitated to agitated. This means that the partition fraction which describes the aerosol content of the head space will increase from IE-10 to IE-8 (see WHC-SD-WM-CN062, Rev. 2 for discussion of partition fractions). The head spare will become much more loaded with suspended material. Furthermore, the nature of this suspended material can change significantly: sluicing could bring up radioactive solids which normally would lay under many meters of liquid supernate. It is assumed that the headspace and filter aerosols in Tank 241-AY-102 are a 90/10 liquid/solid split. It is further assumed that the sluicing line, the headspace in Tank 241-C-106, and the filters on Tank 241-C-106 contain aerosols which are a 67/33 liquid/solid split. The bases of these assumptions are discussed in Section 3.0. These waste compositions (referred to as mitigated compositions) were used in Attachments 1 through 4 to calculate survey meter exposure rates per liter of inventory in the various system components. Three accident scenarios are evaluated: a high temperature event which melts or burns the HEPA filters and causes releases from other system components; an overpressure event which crushes and blows out the HEPA filters and causes releases from other system components; and an unfiltered release of tank headspace air. The initiating event for the high temperature release is a fire caused by a heater malfunction inside the exhaust dust or a fire outside the duct. The initiating event for the overpressure event could be a steam bump which over pressurizes the tank and leads to a blowout of the HEPA filters in the ventilation system. The catastrophic destruction of the HEPA filters would release a fraction of the accumulated filter loadings and would lead to an unfiltered pathway from the radioactively contaminated and toxic aerosols in the head space (vapor space) of the tank into the outside environment. The initiator for the unfiltered (continuous) release scenario is wetting of the HEPA filters with an accompanying filter breach or failure of the seals surrounding the filter in the enclosure. No releases from the filters themselves are assumed in this scenario. In the absence of controls, the exhaust system would continue to expel the contaminated head space air into the outside environment in all three of these scenarios.},
doi = {10.2172/10148994},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Aug 11 00:00:00 EDT 1998},
month = {Tue Aug 11 00:00:00 EDT 1998}
}

Technical Report:

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  • This report documents the chemical compatibility of waste types within tanks 241-C-106, 241-AY-101, and 241-AY-102. This information was compiled to facilitate the transfer of tank 241-C-106 waste to tank 241-AY-102 utilizing supernatant from tank 241-AY-101 as the sluicing medium. This document justifies that no chemical compatibility safety issues currently understood, or theorized from thermodynamic modeling, will result from the intended sluice transfer operation.
  • This report documents the chemical compatibility of waste types within tanks 241-C-106, 241-AY-101, and 241-AY-102. This information was compiled to facilitate the transfer of tank C-106 waste to tank AY-102 utilizing supernatant from AY-101 as the sluicing medium. This document justifies that no chemical compatibility safety issues currently understood, or theorized from thermodynamic modeling, will result from the intended sluice transfer operation.
  • This calculation note analyzes headspace concentrations of hydrogen dependent upon assumed ventilation flow rates provided for tanks 241-C-106 and 241-AY-102. The analyses are based on measured or estimated steady state hydrogen release rates. Tank 241-C-106 is analyzed prior to sluicing; tank 241-AY-102 is analyzed both prior to and after completion of sluicing. Specific analyses, using both best estimated and bounding hydrogen generation rates, include the minimum primary ventilation flow rates required in the tanks to ensure that the steady state hydrogen concentration in the respective tank headspace does not exceed 25% and 100% of the LFL. The headspace hydrogen concentrationmore » as a function of time as well as the time required to reach 25% and 100% of LFL upon complete loss of active ventilation, starting from the steady state hydrogen concentration based on a 200 CFM minimum flow rate in tank 241-C-106 and a 100 CFM minimum flow rate in tank241-AY-102. The headspace hydrogen concentration as a function of thee following partial loss of active ventilation (i.e., step changes to l60, l20, 80, and 40 CFM ventilation flow rates) in tank 241-C-106, staffing from a 200 CFM flow rate and the corresponding steady state hydrogen concentration based on the 200 CFM flow rate. The headspace hydrogen concentration as a function of the following partial loss of active ventilation i.e., step changes to 80, 60, 40, and 20 CFM ventilation flow rates) in tank 241-AY-102, starting from a 100 CFM flow rate and the corresponding steady state hydrogen concentration based on the 100 CFM flow rate.« less
  • This test plan describes a sample separation method which will be used to obtain physical measurements and separated 241-C-106 solids and supernate fractions. In addition compatibility of tank 241-C-106 sludge with tank 241-AY-102 supernate will be determined.
  • The retained gas volume can be estimated by several methods. All of these methods have significant uncertainties, but together they form a preponderance of evidence that describes the gas retention behavior of the tank. The methods are (1) an increase in nonconvective layer thickness; (2) a waste surface level rise (surface level effect [SLE] model); (3) the barometric pressure effect (BPE model); (4) direct void measurement; and (5) the consequences of the transfer process. The nonconvective layer thickness can be determined with sufficient accuracy to describe the overall waste configuration by means of temperature profiles or densitometer indications. However, themore » presence of a nonconvective layer does not necessarily indicate significant gas retention, and small changes in layer thickness that could quantify gas retention cannot be detected reliably with the methods available. The primary value of this measurement is in establishing the actual {open_quotes}fluffing factor{close_quotes} for thermal calculations. Surface level rise is not a useful measure of gas retention in Tank 241-C-106 (C-106) since the waste level fluctuates with regular makeup water additions. In Tank 241-AY-102 (AY-102) with the existing ventilation system it should be possible to determine the gas retention rate within 30-60% uncertainty from the surface level rise, should a significant rise be observed. The planned ventilation system upgrades in AY- 102 will greatly reduce the exhaust flow and the headspace humidity, and the evaporation rate should be significantly lower when transfers begin. This could reduce the uncertainty in gas retention rate estimates to around {+-} 10%.« less