?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F261%2F&rft.title=Gas+Concentration+Measurements+in+Underground+Waste+Storage+Tanks&rft.creator=Chapman%2C+Jon&rft.creator=Chung%2C+Young&rft.creator=Drew%2C+Donald&rft.creator=Edwards%2C+David+A.&rft.creator=Fitt%2C+Alistair&rft.creator=King%2C+John&rft.subject=None%2FOther&rft.description=Currently+over+100+underground+tanks+at+the+Hanford+facility+in+eastern+Washington+state+are+being+used+to+store+high-level+radioactive+waste.+With+plans+for+a+long-term+nuclear-waste+repository+in+Nevada+in+place+(though+not+yet+approved)%2C+one+promising+use+for+these+underground+storage+tanks+is+as+a+temporary+waystation+for+waste+destined+for+the+Nevada+repository.+However%2C+without+a+reasonable+understanding+of+the+chemical+reactions+going+on+within+the+tanks%2C+transporting+waste+in+and+out+of+the+tanks+has+been+deemed+to+be+unsafe.%0D%0A%0D%0AOne+hazard+associated+with+such+storage+mechanisms+is+explosion+of+flammable+gases+produced+within+the+tank.+Within+many+of+the+storage+tanks+is+a+sludge+layer.+This+layer%2C+which+is+a+mixture+of+liquid+and+solids%2C+contains+most+of+the+radioactive+material.+Radioactive+decay+and+its+associated+heat+can+produce+several+flammable+materials+within+this+layer.+Two+components+of+particular+concern+are+hydrogen+(H2)+and+nitrous+oxide+(N2O)%2C+since+they+are+highly+volatile+in+the+gaseous+phase.+Though+the+tanks+have+either+forced+or+natural+convection+systems+to+vent+these+gases%2C+the+possibility+of+an+explosion+still+exists.%0D%0A%0D%0AMeasurements+of+these+gases+are+taken+in+several+ways.+Continuous+measurements+are+taken+in+the+headspace%2C+which+is+the+layer+between+the+tank+ceiling+and+the+liquid+(supernatant)+or+sludge+layer+below.+In+tanks+where+a+supernatant+layer+sits+atop+the+sludge+layer%2C+there+are+often+rollovers+or+gas+release+events+(GREs)%2C+where+a+large+chunk+of+sludge%2C+after+attaining+a+certain+void+fraction%2C+becomes+buoyant%2C+rising+through+the+supernatant+and+releasing+its+associated+gas+composition+to+the+headspace.+Such+changes+trigger+a+sensor%2C+and+thus+measurements+are+also+taken+at+that+time.%0D%0A%0D%0ALastly%2C+a+retained+gas+sample+(RGS)+can+be+taken+from+either+the+supernatant+or+sludge+layer.+Such+a+core+sample+is+quite+expensive%2C+but+can+yield+crucial+data+about+the+way+gases+are+being+produced+in+the+sludge+and+convected+through+the+supernatant.%0D%0A%0D%0AUnfortunately%2C+the+measurements+from+these+three+populations+do+not+seem+to+match.+In+particular%2C+the+ratio+r+%3D+%5BN2O%5D%2F%5BH2%5D+varies+from+population+to+population.+r+also+varies+from+tank+to+tank%2C+but+this+can+more+readily+be+explained+in+terms+of+the+waste+composition+of+each+tank.+Since+H2+is+more+volatile+than+N2O+(and+since+there+are+more+sources+of+oxygen+in+the+headspace)%2C+lower+values+of+r+correspond+to+more+hazardous+situations.%0D%0A%0D%0AThis+variance+in+r+is+troubling%2C+since+we+need+to+be+able+to+explain+why+certain+values+of+r+are+lower+(and+hence+more+dangerous)+in+certain+areas+of+the+tank.+In+this+report+we+examine+the+data+from+three+tanks.+We+first+verify+that+the+differences+in+r+among+populations+is+significant.+We+then+postulate+several+mechanisms+which+could+explain+such+a+difference.&rft.date=1997&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F261%2F1%2Fpnnl97.pdf&rft.identifier=++Chapman%2C+Jon+and+Chung%2C+Young+and+Drew%2C+Donald+and+Edwards%2C+David+A.+and+Fitt%2C+Alistair+and+King%2C+John++(1997)+Gas+Concentration+Measurements+in+Underground+Waste+Storage+Tanks.++%5BStudy+Group+Report%5D+++++