a WSRCMS960244 OOdF 940804(cg Dewpoint Internal Gas Pressure and Cheical Coposition of the Gas Within the Free Volue of DWPF Canistered Waste Fors (U) by J R Harbour Westinghouse Savannah River Copany Savannah River Site Aiken, South Carolina 29808 D T Heran S Crurnp T J Miller J McIntosh A docuent prepared for SPECTRUM 1996 at Seattle fro 08/18/96 08/23/96 DOE Contract No DEAC0989SR18035 This paper was prepared in connection with work done under the above contract nuber with the U S Departent of Energy By acceptance of this paper, the publisher and/or recipient acknowledges the U S Governent's right to retain a nonexclusive, royaltyfreelicense in and to any copyright covering this paper, along with the right to reproduce and to authorize others to reproduce all or part of the copyrighted paper I(ITPIIBffT1ON OF THIS DOCUMENT IS UNU &
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DEW POINT, INTERNAL GAS PRESSURE, AND CHEMICAL COMPOSITION OF THE GAS WITHIN THE FREE VOLUME OF DWPF CANISTERED WASTE FORMS D T Hean J R Harbour Westinghouse Savannah River Copany Westinghouse Savannah River Copany en, South Carolina 29808 M e n, South Carolina 29808 (803) 7258725 (803) 7255898 s L Crup Westinghouse Savannah River Copany M e n, South Carolina 29808 (803) 7251872 T J Miller J B McIntosh Aiken, South Carolina 29808 (803) 7251942 Aiken, South Carolina 29808 (803) 7252133 Westinghouse $avannah River Copany ABSTRACT The Defcnse Waste Processing Facility (DWPF) produced 55 canistered waste fors containing siulated waste %lass during the four Waste Qualification capaigns of the DWPF Startup Test Progra Testing of the gas within the free volue of these canisters for dew point, internal gas pressure, and cheical coposition was perfored as part of a continuing effort to deonstrate copliance with the Waste Acceptance Product Specifications Results are presented for six glassfilled canisters The dew points within the canisters et the acceptance criterion of < 20 C for all six canisters Factors influencing the agnitude of the dew point are presented The cheical coposition of the free volue gas was indistinguishable fro air for all six canisters Hence, no foreign aterials were present in the gas phase of these canisters The internal gas pressures within the sealed canisters were < 1 at at 25 C for all six canisters which readily et the acceptance criterion of an internal gas pressure of less than 15 at at 25OC These results provided the evidence required to deonstrate copliance with the Waste Acceptance Product Specifications I INTRODUCTION The Waste Acceptance Product Specifications (WAPS)l for the DWPF canistered waste fors include specifications for the gas within the fiee volue of the canister The canister free volue is that space within the canister not occupied by glass Under noral operating conditions, the free volue will range fro 110 to 75 liters corresponding to a canister 85 to 90% filled with glass The DWPF canisters, fabricated fro 304L stainless steel, becoe coated with a salt layer on the inside surface during glass filling This salt layer results fro volatilization of chloride and sulfate salts fro the pour strea2 Due to the presence of the salt layer, the aount of water within the canister ust be controlled to avoid localized corrosion A dew point liit of 20 C for Westinghouse Savannah River Copany the free volue gas has been iposed to reduce the risk of localized corrosion Foreign aterials are to be excluded fro the DWPF canistered waste fors A ass spectroetry ethod was ipleented3 to analyze the free volue gas to ensure that no foreign aterials were present in the gas phase In a closed syste, any free liquids present in the canister would also partition between the gas and liquid states Therefore, analysis of the gas phase can detect the presence of either foreign gases or fiee liquids To avoid excessive pressurization, the internal gas pressure is liited to 15 at at 25 C iediately after glass filling and sealing A syste was developed3 which allows for the easureent of the internal pressure as well as the dew point of the gas within the fiee volue of the canister In order to deonstrate copliance with the WAPS, data on the internal pressure, dew point, and cheical coposition of the gas within the free volue of selected canisters f d e d during the DWPF Waste Qualification capaigns was required Six canisters were odified prior to filling in order to obtain this data This paper presents the results of the internal pressure, dew point, and cheical coposition easureents on these six glassfiled canisters 11 INTERNAL PRESSURE OF THE GAS WITHIN THE FREE VOLUME The easured internal gas pressures of canisters S00162, S00007, S00210, S00208, SO0405 and SO0410 are shown in Table 1 Since the WAPS 32 criterion liits the internal gas pressure at a teperature of 25"C, the easured gas pressures were converted to a pressure at 25 C using the ideal gas law The internal pressure of all six canisters readily eets the acceptance criterion of less the 15 at (1140 Torr) at 25 C
TABLE 1 MEASURED CANISTER INTERNAL PRESSURE canister SO0162 SO0007 so0210 SO0208 SO0405 so0410 Pressure Teperature 717 249 254 657 692 220 272 283 283 284 689 240 Pressure @25OC ltprrl 69 1 724 247 25 1 650 684 The internal presse depends ainly upon the glass fill height of the canister and on the elapsed tie between iilling and sealing of the Capister Canisters SO0210 and S00208, which were filled to 100 inches, were sealed on the pour turntable within inutes after filling The pressures observed in these two cases were significantly below atospheric pressure In order to achieve these pressures, the average teperature within the canister free volue had to be 630 C at the tie of sealing After the canister then cooled to roo teperature, the internal pressure dropped to 250 TOM The reaining four canisters were not sealed on the pour turntable These canisters were allowed to cool to roo teperature and were then sealed at the next station in the process The resultant internal gas pressures of 675 TOMinside the canister iplies an average free volue gas teperatureof 6QOC at the tie of sealing This teperature results fro heating the nozzle prior to tsealing DEW POINTS OF THE GAS WITHIN THE FREE VOLUME The dew points of the gas within the free volue space of canisters S00162, S00007, S00210, S00208, SO0405 and SO0410 were easured Two hygroeters, calibrated to a tolerance of If: 2"C, were used to easure the dew points The dew points easured for the six Canisters are shown in Table 2 The acceptance criterion is a dew point less than 20 C Therefore, the acceptance criterion was et for all six sisters TABLE 2 MEASURED CANISTER DEW POINTS (DP) GalisbX SO0162 SO0007 SO0210 SO0208 SO0405 so0410 DP #1 50 a160 +02 19 +28 +44 DP #2 50 +135 +o 1 19 +28 +50 Melt Cell DP a 11 12 17 15 16 The dew points within the canisters are a coplex function of several variables: The dew point of the air in the Melt Cell, the tie between filling and sealing, the glass fill height, and the presence of salts within the canisters The dew point of the air in the Melt Cell at the tie of teporary sealing is iportant since it is this air that ends up in the canister free volue space The tie between glass filling and sealing is a second significant variable in deterining the canister dew point This variable deterines the teperature of the free volue air at the tie of sealing For exaple, both canisters SO0210 and S00208, which were sealed within inutes of filling had relatively low dew points due to the high average gas teperature in the free volue space at the tie of sealing A third factor influencing dew points within a canister is the glass fill height Higher fdl heights increase the gas teperature in the free volue and can decrease the aount of water of absorptionby the salt layer as discussed below The dew point result &o canister SO0007 iplies that another factor also plays a significant role in deterining the dew point within a canister It has been observed that salt layers for on the inner canister surfaces during pouring If the canister is not sealed iediately and reains open in the Melt Cell, then water can absorb onto the hygroscopic salt layer When the canister is sealed, the water will equilibrate between the salt and the free volue gas This can result in a higher dew point It is therefore iportant to seal the canister on the pour turntable iediately afbr filling IV COMPOSITION OF THE GAS WITHIN THE FREE VOLUME Data obtained on the gas within the free volues of canisters S00162, S00007, S00208, S00210, S00405, and SO0410 did not reveal any copounds, other than air, to the sensitivity of the equipent The acceptance criterion requires that there be no detectable foreign aterials present in the free gas Therefore, this acceptance criterionwas et The gas within the free volues of canisters S00162, S00007, S00208, S00210, S00405, and SO0410 was analyzed using ass spectroetry Scans fro 1 to 200, 1 to 50,40 to 95, and 90 to 200 ass units of the canister free volue gas were obtained These data were copared to equivalent scans taken fro roo air Ak was defined as the standard since the gas within the free volue space of the canistered waste for should contain only air fro the Melt Cell No differences between the coposition of the gas in the free volues of the canisters and the roo air were found Scans using a ultiplier to increase the sensitivity of the technique were also perfored fro 45 to 90 and fro 90 to 200 ass units These scans cover the ass unit region where foreign aterials would be expected No differences were noted between these scans and the equivalent scans of air
Two ethods were used to estiate the sensitivity of the Extrel Questor 11process ass spectroeter The fwst ethod used isotopes of argon as a sensitivity indicator with the Ar38 isoer present at 6 pp The second ethod used benzene concentrationsof 1, 10, and 100 pp in air Both techniques deonstrated sensitivities of less than 10 pp, with an estiate of the actual sensitivity of 5 pp The lack of detection of foreign aterials in the free volue gas was therefore bounded by this sensitivity value CONCLUSIONS Results on the internal gas pressure, dew point, and cheical coposition were,obtained fio six canistered waste fors produced during the DWPF Waste Qualification capaigns These results deonstrated that the Waste Acceptance Product Specificationswere et for these properties In all cases, the internal pressures of the sealed canisters were below atospheric and readily et the acceptance criterion of 15 at at 25OC When the canjstess were sealed within inutes of glass f a i g, the internal pressures were reduced to 032 at The cheical coposition of the gas within the six canisters tested was indistinguishable fro air This iplies that there were no foreign aterials within the gas phase and that there were no fiee liquids in equilibriu with the gas phase in the canisters The sensitivity of the ass spectroetric easureents was 5 pp Finally, the easured dew points of the six canistered waste fors were all less than the acceptance criterion liit of 20 C Lower values of dew point were obtained when the canisters were sealed on the pour turntable within inutes of f a i g If the filled canister is allowed to cool prior to sealing, additional water can be absorbed by the salt layer This can result in a higher dew point after sealing Clearly, the preferred option is to seal the canisters within inutes of glass filling since the lower dew points and internal pressures will further reduce the likelihood of l d i z e d l corrosion of the stainless steel canisters ACKNOWLEDGEMEiNTS This paper was prepared in connection with work gerfoed under contract No DEAC0989SR18035 with the U S Departent of Energry REFERENCES 1 "Waste Acceptance Product Specifications for Vitrified HighLevel Waste Fors'', Office of Environental Manageent, USDOE Docuent 0093, Rev 1 (1995) 2 M K Andrews, J R Harbour, C A Cicero, D T H e a and N E Bibler, "Salts in the Interior of DWPF Canistered Waste Fors", WSRCTR950455, (1995) 3 J R Harbour, T J Miller, and M J W t a k e r, "Exclusion of Foreign Materials fro the SIPS Canistered Waste Fors: Characterization of the Gas within the Free Volue", hoc of the Second International Conference on HLRWM, A p d 28 May 3, 1991, p 728, Aerican Nuclear Society, La Grange Park, Illinois (1991)