1、Designation: C1751 11Standard Guide forSampling Radioactive Tank Waste1This standard is issued under the fixed designation C1751; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses in
2、dicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide addresses techniques used to obtain grabsamples from tanks containing high-level radioactive wastecreated during the reprocessing of spent nuclear f
3、uels. Guid-ance on selecting appropriate sampling devices for wastecovered by the Resource Conservation and Recovery Act(RCRA) is also provided by the United States EnvironmentalProtection Agency (EPA) (1).2Vapor sampling of the head-space is not included in this guide because it does notsignificant
4、ly affect slurry retrieval, pipeline transport, plug-ging, or mixing.1.2 The values stated in inch-pound units are to be regardedas standard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with it
5、s use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1129 Terminology Relating to Water3. Terminology3.1 DefinitionsFor def
6、initions of terms used in thismethod, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 forced evaporation, nintentional concentration of awaste solution using heat or vacuum, or both, primarily toremove water or other solvents.3.2.2 pH modified, na description of a
7、 solution where thepH is adjusted with either an acid or base material to achievea desired pH level to minimize tank corrosion.3.2.3 soft sludge, na sludge with a low viscosity whereminimal sampling device pressure could be used to penetratethe sludge layer.3.2.4 sparge, na process of delivering a c
8、hemically inertgas through fluids to displace materials for the purpose ofmixing.3.3 Acronyms:3.3.1 EREEExtended Reach End-Effector3.3.2 HASTHighly-Active Storage Tanks3.3.3 LDUAsLight-Duty Utility Arms3.3.4 NPHNormal Paraffin Hydrocarbons3.3.5 ORNLOak Ridge National Laboratory3.3.6 PTFEPolytetraflu
9、oroethylene3.3.7 PVCPolyvinyl Chloride3.3.8 RFDReverse-Flow Diverter4. Significance and Use4.1 Obtaining samples of high-level waste created duringthe reprocessing of spent nuclear fuels presents unique chal-lenges. Generally, high-level waste is stored in tanks withlimited access to decrease the po
10、tential for radiation exposureto personnel. Samples must be obtained remotely because ofthe high radiation dose from the bulk material and the samples;samples require shielding for handling, transport, and storage.The quantity of sample that can be obtained and transported issmall due to the hazardo
11、us nature of the samples as well astheir high radiation dose.4.2 Many high-level wastes have been treated to removestrontium (Sr) or cesium (Cs), or both, underwent liquidvolume reductions through forced evaporation or have been pHmodified, or both, to decrease corrosion of the tanks. Theseprocesses
12、, as well as waste streams added from multipleprocess plant operations, often resulted in precipitation, andproduced multiphase wastes that are heterogeneous. Evapora-tion of water from waste with significant dissolved saltsconcentrations has occurred in some tanks due to the high heatload associate
13、d with the high-level waste and by intentionalevaporative processing, resulting in the formation of a saltcakeor crusts, or both. Organic layers exist in some waste tanks,creating additional heterogeneity in the wastes.4.3 Due to these extraordinary challenges, substantial effortin research and deve
14、lopment has been expended to developtechniques to provide grab samples of the contents of thehigh-level waste tanks. A summary of the primary techniques1This practice is under the jurisdiction of ASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.13 on Spent
15、 Fueland High Level Waste.Current edition approved June 1, 2011. Published July 2011. DOI: 10.1520/C1751-11.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
16、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used to obtain samples from high-level waste
17、 tanks is providedin Table 1. These techniques will be summarized in thisguideline with the assumption that the tank headspace isadequately ventilated during sampling.5. Liquid-Only Sampling Techniques5.1 Liquid only techniques are not common in tank wastesampling. More common are liquid samples cap
18、tured bymethods used primarily to obtain solid or slurry samples.However, some high-level waste tanks, such as the Highly-Active Storage Tanks (HAST) tanks at Sellafield in the UnitedKingdom, had sampling systems installed in the tanks beforethe high-level waste was added. The HAST system uses aneed
19、le orifice as part of a Reverse-Flow Diverter (RFD) toobtain samples. The needle orifices are easily plugged byparticles; only liquid samples can be obtained by this system.The HAST system design also allows for the agitation of tankcontents to help obtain representative liquid samples (2).6. Slurry
20、/Liquid Sampling Techniques6.1 The simplest of the liquid sampling techniques is dipsampling. At the Hanford Site, this sampling technique is oftenreferred to as “bottle on a string.” Only liquid or slurry samplescan be taken by this method. Samples can be taken at variousdepths in the tank to deter
21、mine whether there is verticalheterogeneity in the tank. If data on the stratification in the tankis not needed, waste in the tank should be sparged or mixedbefore taking the sample to decrease sampling bias.6.2 A dip sample is taken by lowering a stoppered andweighted bottle into the waste to the d
22、esired depth. After thebottle has reached the desired level, the stopper is pulled fromthe bottle and the liquid or slurry sample flows into the bottle.Ideally, the stopper is then closed and the bottle is pulled fromthe tank (3).6.3 Dip sampling is limited to lower viscosity liquid andslurry materi
23、als and the effectiveness of sampling is highlydependent upon the size of the sample bottle inlet and thepresence of saltcake layers which may prevent sampling accessto lower tank levels. Further, sampling locations are limitedonly to vertical columns directly under a tank penetration, orriser. Part
24、iculates obtained from this method may be highlybiased due to sample location and variations in settling velocitywhile sampling.6.4 Liquid samples from radioactive-waste tanks have alsobeen obtained using a vacuum-pump system. Samples werepulled by vacuum from the specified level in the tank through
25、polytetrafluoroethylene (PTFE) tubing into a sample jar; ifnecessary, the sample jar could be shielded. A stainless-steelpipe nozzle is attached to the bottom of the PTFE tubing toTABLE 1 High-Level Waste Tank Sampling MethodsTechnique Material Type NotesSolid Slurry LiquidHAST in-tankneedle orifice
26、X Orifice as part of Reverse-FlowDiverter (RFD)Bottle on a String X X Dip sampleVacuum Pump X XAuger X X Only high viscosity slurriesSample Cup X X Manual system used atSavannah River Site to obtainsalt-cake samples and hardsludges that dont slump.Core Drilling Rotary Mode(Hanford Sampler)X X Hard s
27、ludges and salt-cake.Core Drilling Push Mode(ORNL SoftSludge Sampler)X X Liquid or soft sludges.Cylinder withretractablenose coneX X Used at Savannah River Sitefor soft sludges and liquids.Robotic Arm X X X Material type captured isdependent upon the end-effector.Hydraulic Mining X X XHydraulic Scoo
28、p X X XSample Thief(Bacon Bomb)XC1751 112keep it vertical. A diagram of the vacuum-pump samplingsystem used at Oak Ridge National Laboratory (ORNL) isprovided in Fig. 1 (4).7. Solids/Slurry Sampling Techniques7.1 Early sampling of the solids content of Hanford tankwastes was by the use of an auger.
29、Auger samples were takenonly from the surface of the waste and were limited to 6 in.This 6 in. limitation was driven primarily by a desire to reduceradiation dose. Some homogenization of the sample occurswhile obtaining auger samples. These samples can only betaken directly beneath a penetration, or
30、 riser (5).7.2 Auger samples are taken by encasing an auger in ashroud to contain the sample. The auger is rotated through thesample while the shroud remains stationary. Sample is col-lected along the flutes of the auger. Liquid is generally notcontained in the auger unless it is associated with sol
31、ids in theform of a sludge or highly viscous slurry.7.3 Savannah River Site staff developed a manual method ofcapturing salt-cake samples from waste tanks. This methodincorporates a sample cup pinned to a handle that can be driveninto the salt cake. The cup has a sharp edge to allow it to cutthrough
32、 the salt cake as the handle is pounded with a hammer.The bore of the cup has a ledge like a fishhook barb thatcaptures the material once it is forced into the cup. The cupdesign is shown in Fig. 2 (6). The applicability of this methodis limited to hard materials that will not flow or slump oncecoll
33、ected in the sample device.7.4 Core drilling is the primary mechanism for obtainingsamples from the Hanford waste tanks. A core-drilling truckwith a shielded handler was specifically designed for thispurpose. Two modes, push or rotary, can be used to obtainsamples. Liquids, slurries, and soft sludge
34、s can be obtained inpush mode; rotary-mode sampling must be used to obtainsamples of harder sludges and salt-cake. Only minimal successhas been achieved when sampling saltcake.7.5 The Hanford Sampler is based on a modified core-drilling design that is similar to the thief-and-trier-type sam-plers. D
35、etails of the core-drilling truck procedure are providedin Waste Characterization Plan for Hanford Site Single-ShellTanks (7), (8). Liquid and solid samples are trapped in thesampler by a spring-actuated rotary valve (see Fig. 3). Twodifferent sampler designs have been used, but both designsincorpor
36、ated the spring-actuated rotary valve. The first designproduced samples that were 19 in. long and 1 in. in diameter.The later design had a slightly larger diameter (1.25 in.). It isimportant to note the design length of this sampler was drivenby operational space limitations of the existing hot cell
37、s at thetime. Core samples can be taken at varying depths to obtainsamples that comprise the entire depth of the waste. A slidingpiston in the sampler controls the height of the sample beingcollected. A hydrostatic fluid is added via the drill string toFIG. 1 Vacuum Pump Sampling SystemC1751 113keep
38、 the waste from slumping into the void created by thesample when the sampler is pulled from the tank. Normalparaffin hydrocarbons (NPH) were initially used as the hydro-static fluid. Nitrogen gas has also been used.FIG. 2 Savannah River Site Salt-Cake Sample CupFIG. 3 Hanford Core SamplerC1751 1147.
39、6 A sampler based on the same principle was used atORNL to obtain samples of soft sludges from waste tanks atthat site. Samples are collected by manually pushing a polyvi-nyl chloride (PVC) pipe with a detachable handle assemblyinto the sludge in the tank. A bottom closure that can becontrolled from
40、 above by the operator is incorporated into thesampler Fig. 4. This sampler is capable of capturing both liquidand soft sludge samples. A brief description of the operation ofthis sampler is provided in an ORNL technical documentdescribing the sampling and analysis of radioactive waste tanks(4).7.7
41、The Savannah River Site developed a similar method forobtaining soft sludges. The sampler is a cylinder with aretractable nose cone at the bottom. Sections of pipe are addedto the sampler to lower it to the desired depth in the tank.Penetration into the sludge is achieved by using the collectiveweig
42、ht of the sampler and pipe sections. Once the desireddepth is achieved, the nose cone is retracted into the cylinder,forming an annulus between the cone and cylinder. Gases andliquids pass through a vent at the top of the cylinder, allowingthe sludge to be trapped in the cylinder. After the cylinder
43、 isclosed, the sampler is raised out of the tank into a shielded cask(9).8. Other Sampling Techniques8.1 Robotic arms have also been deployed in waste tanks toretrieve samples. Light-Duty Utility Arms (LDUAs) are mo-bile, multi-axis positioning systems that can access tankcontents through the risers
44、. The LDUAs provide a flexiblerobotic deployment platform for many applications, includingsampling. Using the Extended Reach End-Effector (EREE),waste samples have been retrieved from Hanford tanks forlaboratory analysis. The extended-reach arms allow samples tobe taken throughout the tank, not just
45、 directly under risers.Samplers are detachable from the arm and can be designed toobtain samples of different volumes. Current samplers have aclamping force of 50 to 300 lbs and can capture both liquidsand solids (10).8.2 Several other systems for obtaining liquid and solidsamples from radioactive w
46、aste tanks have been proposed buthave not been tested extensively. These methods includehydraulic mining, hydraulic scoop, and bacon bomb samplers.8.3 Hydraulic mining can be performed in several differentways to obtain different fractions of waste components. Slur-ries can be obtained by inserting
47、a tube into the waste tank,generally through a riser. Water or other appropriate fluid ispumped down the tube at a flow rate and velocity high enoughto suspend the non-soluble components of the waste. A portionof the solution is retrieved by pulling it up another passage inthe sampling housing. Samp
48、les of the soluble components ofthe waste can be obtained by a similar procedure with lowerflow rates and velocities such that the non-soluble fractions arenot suspended. Non-soluble components can be sampled byplacing a filter at the bottom of the sampling housing andallowing the water to pass thro
49、ugh the filter and remain in thewaste tank. The filter is pulled up to the top of the tank andtaken to a hot cell to open the container and perform the desiredanalyses (6).8.4 Hydraulic scoops can be used to obtain liquids, sludges,and slurries. The scoop is opened and lowered into the tank tothe desired level. Once the scoop has sunk to the desired level,the scoop is closed, capturing the sample. The scoop is thenraised out of the tank. Mechanically controlled scoops areselected when the introduction of organic-based hydraulicfluids are not allowed in the tank.8.5
