A study is being conducted of the resources and planning that would be required to clean up an extensive contamination of the outdoor environment. As part of this study, an assessment of the fleet of machines needed for decontaminating large outdoor surfaces of horizontal concrete will be attempted. The operations required are described. The performance of applicable existing equipment is analyzed in terms of area cleaned per unit time, and the comprehensive cost of decontamination per unit area is derived. Shielded equipment for measuring directional radiation and continuously monitoring decontamination work are described. Shielding of drivers' cabs and remote control vehicles is addressed

Barbier, M.M.

Chester, C.V.

Barbier, M. M.

Chester, C. V.

UNT Digital Library

NOTICEPORTIONS OF THIS REPORTIt has been reproduced from th« bestavailable copy to permit the broadestpossibleDECONTAMINATION OF LARGE HORIZONTALCONCRETE SURFACES OUTDOORS*MASTERMarcel M. BarbierMarcel M. Barbier Scientific Consulting3003 Rayjohn LaneHerndon, Virginia 22070Conrad V. ChesterEnergy DivisionOak R'.dge National LaboratoryP. 0. Box XOak kidge, Tennessee 37830By acceptance of this article, the publisher orrecipient acknowledges the U. S. Government's rightto retain a non-exclusive, royalty-free license inand to any copyright covering the article.Research sponsored by the U.S. Department of Energy under contractW-7405-eng-26 with the Union Carbide Corporation.DISTRIBUTION OF f l i iS DOCUMENT IS UNUWTE0DECONTAMINATION OF LARGE HORIZONTALCONCRETE SURFACES OUTDOORS*Marcel M. BarbierMarcel M. Barbier Scientific Consulting3003 Rayjohn LaneHerndon, Virginia 22070Conrad V. ChesterEnergy DivisionOak Ridge National LaboratoryP. 0. Box XOak Ridge, Tennessee 37830A study is being conducted of the resources andplanning that would be required to clean up an extensivecontamination of the outdoor environment. As part ofthis study, an assessment of the fleet of machinesneeded for decontaminating large outdoor surfaces ofhorizontal concrete will be attempted. The operationsrequired will be described. The performance of applic-able existing equipment will be analyzed in terms ofarea cleaned per unit time, and the comprehensive costof decontamination per unit area will be derived.Shielded equipment for measuring directionalradiation and continuously monitoring decontaminationwork will be described.Shielding of drivers' cabs and remote controlvehicles will be addressed.*Research sponsored by the U.S. Department of Energy under contractW-7405-eng-26 with the Union Carbide Corporation.INTRODUCTIONA study of the logistics and tasks for a large-scale decontaminationof the environment is underway at ORNL as part of the Emergency TechnologyProgram conducted for the Operational and Environmental Safety Divisionof the Department of Energy. The study is considering a situation inwhich contamination is initially deposited by aerosol on surfaces andhas been rained on. In contrast to much decontamination and decommis-sioning experience, it is assumed that there has been relatively littletraffic on the affected surfaces.In such a situation, most of the area that would be affected wouldbe unpaved. However, decontamination of the few percentage of pavedarea would have a high priority and a certain amount of time urgency ina large operation to provide access to the affected area and pathwaysfor logistic support. It is also assumed that decontamination methodsused must pick up the contamination rather than simply flush it down astorm drain or into the surrounding soil or drainage system. In concept,something like a large vacuum cleaner is required, operating in conjunctionwith a method of providing a controllable amount of abrasion or erosionof the surface. It is expected that the contamination will be tightlybonded to the surface or trapped in surface porosity or cracks, andwould be largely unmoved by the usual street vacuum sweeper.However, there is hard wire-brush-street-sweeping equipment whichcan remove a limited portion of the surface layer. For contaminationtrapped in deeper pores or cracks, road planers may be useful. Theseabrade the surface with hardened steel bits and may be adjusted toremove the surface to a depth ranging from a few millimeters to severalcentimeters.With appropriate modifications, these machines should produce theleast volume of waste and in a simple form—a freeflowing powder.Use of high-pressure water jets for cutting rock and concrete is aproven technology. They would be advantageous for concrete surfaceremoval in that there are no bits to replace. Unfortunately, there isno commercial waterjet equipment developed for continuous removal ofbroad surface areas. Existing equipment is single-nozzle, semiportableequipment for cutting small areas. Equipment could be developed forroad surface decontamination, but it would require a major effort.The addition of large amounts of water to the waste would complicatespoil removal. The water would make much more difficult the design andoperation of the air filters required on equipment for continuous vacuumingof the cutting area.WIRE-BRUSHING OF CONCRETE ROADSThe commercial equipment available is simply a street sweeperequipped with hard steel-wire brushes. These machines usually have twovertical-axis gutter brooms and one horizontal axis main broom, plus aconveyor that loads the fines into a box, the contents of which can bedumped into a truck. They are shown in Figs. 1 and 2, one is manufacturedby Athey Products in Wake Forest, North Carolina, and the other by FMC,Pomona, California.By exerting sufficient pressure downwards on the brooms and lettingthem rotate at high speed, an abrasive action is exerted on the pavement.It changes color, and the hollows in the surface are swept clean.Exactly how much surface layer thickness is removed is not known.Tests with chemicals identical to the fall-out should be performed tocheck to what measure they are removed.Table 1 gives the costs for the two street sweepers considered. Thecost per square meter is $0.004--i.e., $4,000/km ($11,000/mi ). We haveassumed 10 years lifetime and 1200 working hours per year as representativeof this kind of equipment.Fig. 1 Athey Mobilsweeper.Fig. 2 FMC Mechanical Sweeper.Table 1: Performance and Cost of Wire Brushing Equipment.Manufacturer Sweeping Sweeping Area/ Crew Purchase Ownership Maintenance Labor Total Cost//Model Width Speed Unit time Size Price Cost Costs Costs Costs Unit Area(m) (m/h) (m2/h) (k$) ($/h) ($/h) ($/h) ($/h) ($/m2)Athey/ 3.048 2475 7543 1 48 7.5 6 18 31.5 0.0042Mobilsweeper IIFMC 3.25 2475 8044 1 60 9 6 18 33 0.0041MechanicalSweeper 12CUTTING OF CONCRETE ROADS WITH COLD PLANERSThe road construction industry provides machines to cut away concretesurface layers with hard bits.We have taken from each of three major manufacturers (Dresser inGal ion, Ohio, CMI in Oklahoma City, Barber-Greene in Aurora, Illinois) alight model, a middle model and a heavy model to compare them in termsof performance and cost. These models are shown in Figs. 3 through 10.As cutting depths we have taken 6 mm, 12 mm and 25 mm. It isestimated that all chemical contamination is contained in the first 6mm. Irregularities of level in the road surface are usually less than25 mm.It is estimated by CMI that the cutting speed can be 15 meters perminute for a cut of 6 mm, !2 m/min for 12 mm, and 6 m/min for 25 mm inaverage concrete.For the purpose of our calculations, it seems reasonable to assignthe 6 mm cutting depth to the light model, the 12 mm to the middle oneand the 25 mm to the heavier one.The duty factor of such machines has been assumed to be 600 hrs/yr.There seems to be a consensus in the industry that this is a nationwideaverage, due to the working conditions, assignments, weather, etc. Costcalculations are generally made on such a basis.Lifetimes of most road planers are given as 5 years (CMI, Barber-Greene), Dresser suggests 10 years for its Galion models.Each manufacturer has its own way of making cost calculations. Wehave used the ownership costs, the operating costs, and the labor costsas given by each manufacturer without modification, in order to be ableto make comparisons.The maintenance costs usually do not include the replacement of thecutting cits because the wear of this item is so much dependent on theCOT - la,& .a>ccaF-Ha.•aaoOt_uCOoX•Hotoft.§osI• H10Pioc03•a,"Soo3ot-,ouiin0)tiQ•HteiFig. 6CMI Pavement Profiler PR-275-RT.12Fig. 7 CMI Pavement Profiler PR-525.5 •: w:" :; «̂::c;!8i l i i # y « t e « ;CMI Pavement Profiler PR-750.14va"S.0>oOL3a03• H15i na§Doote3o16hardness of the concrete to be cut. We asked the various manufacturersto recommend methods of calculation for this cost item and got differentanswers.Dresser indicated that its figures are based on the replacement ofthe bits every 8 hours.CMI referred us to a manufacturer of bits (Kennametals in Bedford,Pennsylvania), who suggested 5000 to 6000 square meters as the areaafter which the whole set of bits has to be changed on the mandrel.Barber-Greene suggested a figure of 0.5-1 ton of cut material perindividual bit to be changed.The cost of one bit is $4. The number of bits per mandrel is givenby the manufacturer for each model.2We have used the recommended methods in each case, using 5000 m ofcut area per change of bits for the CMI machines and 0.75 ton of cutmaterial for the Barber-Greene machines.The labor costs are also different—the size of the estimated crewvarying as well as the assumed salaries and burden rates.Table 2 shows the performance and hourly costs of the road planers.The final cost, of the cutting operation lies in the range of $0.18 to$0.59/m depending on depth of cut and type of machine. The deeper cutsare more expensive than the shallower ones, but not in proportion totheir depths because larger machines are used. Usually one gains for agiven depth in going to a larger machine. However, only the smallermachines can maneuver around sharp curves and man-holes.The cost of the cutting operation per square kilometer would thereforelie in the. range'from $180,000 to $590,000, and per square mile in therange from $500,000 to $1,600,000.The machines are compared for constant depth in Table 3. Notincluded are the costs of using trucks to carry away the rubble. TheTableJ i Performance and Cost of Road Cutting Equipment.Manufacturer/ModelDresser/GalionRoad PlanerRP 12RP 30/42RP 60CM!/PavementProfilerPR-275-RTPR 525PR 750Barber/GreeneDynaplaneRX-40RX-75RX-75Bits39128180136176247117179210CuttingWidth(m)0.3141.0661.5242.0322.6423.781.8753.153.725Depth(cm)0.6251.252.50.8251.252.50.6251.252.5CuttingSpeed(m/h)900720360900720360900720360Area/Unittime(m2/h)283768549182919021361168822681341MMMMCrewsize1112224: 44PurchasePrice(k$)50112135189280348221358363OwnershipCosts($/h)153645889911890146143MaintenanceCosts($/h)11161829567190105115BitsCosts($/h)194797199268270129348452LaborCosts($/h)181818202020757575TotalCosts($/h)63117178336443479397709790Cost/Unit area($/m2)0.220.150.32. vj0.180.230.350.240.310.59Table 3 . Comparison of Road Cutting Machines for Equal Cutting Depth (1.25 cm)ManufacturerModelDresser/GalionRoad PlanerRP 12RP 30/42RP 60CMI/Pavement ProfilerPR-275-RTPR 525PR 750Barber/GreeneDynaplaneRX-40RX-75RX-75andCuttingWidth(m)0.3141.0661.5242.0322.6423.78-1.8753.153.725Speed (720Area/Unit time(m2)2267681097146319022722135022682682m/h).OwnershipCosts($/h)153645889911890146149MaintenanceCosts($/h)11161829567190105115BitsCosts(<7h)194797159268540207348411LaborCosts($/h)U1818202020757575TotalCosts($/h)63117178296443749462709750Cost/UnitArea($/m)0.280.150.160.200.230.280.340.310.2819larger CMI and Barber-Greene machines are equipped with conveyors topick up the rubble and load it into trucks. In the other cases force-feed loaders or vacuum pick-up equipment (for lighter rubble) have to beutilized as well.MODIFICATION OF MACHINES FOR DECONTAMINATION OPERATIONEquipment for cleaning or removing surfaces will require varyingmodifications for decontamination operations, depending on the hazard ofthe material removed.A system for picking up the removed material will be required inany case. Measures to prevent scattering of the contamination willgenerally be necessary. One approach is to enclose the cutting orbrushing operation in a hood and connect it to powerful mobile vacuumingequipment. Figures 11, 12 and 13 lightly indicate location of the hood.Where the operation produces heavy cuttings, as in some road planing,the mechanical cutting removal system will have to be enclosed in thevacuum system (Fig. 13).CAB SHIELDINGFor most applications, an enclosed cab with a filtered air supplywill be required. For intermediate levels of fission product contamination,the cab will require shielding against beta radiation producing the highsurface dose. A cab for one operator requires a surface of the order ofp 2 21 0 m , a cab for 2 operators, 16 m . With 3 g/cm to get rid of thebetas, one arrives at a weight of 300 kg. If one adds this to theradiation monitor (700 kg), one arrives at 1000 kg added weight to thevehicles. The street sweepers have a water-carrying capacity of thatorder that is not needed here. The road planers are heavier machinesthat can easily accommodate that type of surcharge.207'(2375mm)(2826mm)10'4V';"(315Gmm)6"0" (1G29mm)—7'10VV'(2400mm)\ tKi _ JFig. 11 Shomalic View of Dresscr/GnHon RP GO Rood Planer.21• / . . .I• i \V;L.3 (Din -juII<CM•rl[JL,"Tiii? -TTli d(3.04 r-.m) ALL wrC^VATOS. '.LL'Jf.TnATiONS AND SPECIF:CAT!O\'S CCN'AIVEO HE?E'N. A«?E2ASED ON T!'C LA T r S" PRCCjCT !\rOrt l/ATi0V AVA'IA9LF AT T'VE Cr c-JSLlC/"-TfCN. THE '•I'iHT IS FSSERVEO TC !.'AKl= C-iANGES AT ANYTlS/.S.VrtTi-CuT NCT'CE 0=;Cfl'-ltAT'ON.ts)Fig. 13 Shematic View of CMI PR 525 Pavement Profiler.23Of major interest is the operator shielding that can be obtainedfor the weights that can reasonably be added to the machines with minormodifications but without redesign. Street sweepers are quoted as beingable to carry 1 additional metric ton; whereas, more is possible with thelighter road pljners and certainly 5 tons and more for the heaviermodels. To attenuate 2 MeV gammas by a factor 10 requires 2.3 attenuationolengths, or 57.6 g/cm (5.1 cm or 2 in. of lead) giving 5.76 metric tons2for a 1 man cab of 10 m . In fact, it is more like 7.5 metric tonsbecause there is a build-up factor of the order of 2 at that energy inlead for an attenuation of 10. This weight is probably the limit foradditional loading on the medium road planers. For reduction factorsabove 10 for gamma radiation, one will have to resort to remote controlof the vehicles.RADIATION MONITORA speculative development would be a collimated radiation monitorto scan the surface being removed for contamination level. It may bepossible to provide feedback to the cutter to minimize the amount ofmaterial removed.A typical solid angle for the measurement could be that subtendedby a circle of 30 cm radius at a distance of 150 cm. This represents1/100 of the total spherical solid angle 12.56 steradian. A decontaminationfactor of 100:1 would be difficult to exceed in one pass. Therefore theAcounter should in principle be shielded for an attenuation of 10 .Radiation from fission products has two major components: betasand gammas, which carry roughly the same amount of energy. Their energyspectrum is also comparable and extends up to several MeV. However, thesurface aose in soft tissue deposited by the betas is very much largerthan that deposited by the gammas. As an example at 1 MeV energy, ittakes 3 x 10 betas per square centimeter to produce 1 rad; whereas, it24Qtakes 2 x 10 gammas per square centimeter to do the same, i.e., a ratioof 70:1. The betas are easily stopped. At an energy of 6 MeV, which isabout the limit to which the beta spectrum extends, the range of electrons2in matter is about 3 g/cm , or 0.25 cm of lead. The gamma spectrum israther constant to about 2 MeV and falls off thereafter.Given the high energy of the radiation and the high attenuationrequired from the shield, one has an interest in taking the smallestpossible detector to minimize shield size. Recently, cadmium telluridechips have been introduced. These chips have as high a sensitivity assodium iodide per unit volume and can be made in wery small sizes. As aresult, one has practically a point-like detector, which is still ableto measure accurately radiation levels of the order of 0.1 mrem/hr.2 -1Taking the narrow-beam, mass attenuation coefficient of 0.04 cm g2for 2 MeV gammas, leading to an attenuation length of 25 g/cm , andassuming that the beta/gamma sensitivity ratio of the detector is largeenough to compensate for the gamma build-up factor in the shield, oneends up with a weight of 700 kg for the shield, resolved that one willmeasure the betas. More elaborate calculations will show if it ispossible to reduce the shield weight below the figure given above, whichis already not negligible f~r a vehicle.A sketch of the shield is shown in Fig. 14.REMOTE OPERATIONFor high-level contamination, remote operation would be considered.The technology is well developed.Remotely operated vehicles have been designed and tested for roadand airborne uses. They are equipped with head-aimed TV systems, videodata links, telemetry, command data links, and vehicle control actuators.One industrial source, having developed remotely operated vehicle control,quotes figures of the order of $200,000 for a feasibility study including25Pig. 14 Section through Pecontnimtintioti Monitor.26system assembly and preliminary tests (excluding the vehicle cost). Forsubsequent systems derived from the above, but procured in quantities often or more, adaptable to different types of vehicles, an estimate of$100,000 has been obtained.MACHINE DECONTAMINATIONDepending on the machine and the intensity and type of contaminationbeing removed, it may be desirable to modify the machine in order tofacilitate its decontamination prior to maintenance work. This would,among other things, include covering complex portions and reentrantsurfaces with a removable cover or coating. Wheels or tracks may befitted with disposable covers.CONCLUSIONSThere are a number of high-production commercial machines whichshould be adapable to removing tightly adhering contamination from largehorizontal surfaces. These include street sweepers with hard wirebrushes and road planers. Wire brushing can be accomplished in a non-toxic environment for about $0.004/m . A single large machine can cover2about 9 km per year. Road planing, grinding off the surface 12 mm, can2be carried out in a non--toxic environment for about $0.3/m . Large2machine productivity is about 1.5 km per year.These machines would require considerable modification for operationin a radioactive environment, including enclosure of the cutting tool,attachment of mobile vacuum pickup, possibly shielded cab, possiblyremote control, and provisions to simplify decontamination of the machineprior to maintenance.The great difference in cost between brushing and planing suggeststhat if brushing is at all effective, it should be attempted first.These methods, even with the cost increases from machine modificationand contaminated operations, should remove contamination for substantiallyless cost than manual methods or pavement removal. The volume of contami-nated waste should be significantly reduced.Because the effectiveness of the decontamination operation willdepend heavily on the nature of the contamination as well as the concretesurface, it must be verified experimentally for a given set of conditions.The feasibility of developing high-production, large-area equipmentfor concrete decontamination using high pressure water jets should beexamined.

Decontamination of large horizontal concrete surfaces outdoors

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