ML20204C222
| ML20204C222 | |
| Person / Time | |
|---|---|
| Site: | 02700043 |
| Issue date: | 07/18/1986 |
| From: | Thomas Nicholson NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Beratan L NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| NUDOCS 8607310079 | |
| Download: ML20204C222 (11) | |
Text
, . Dis tribution/R-2811:
Circ /Chron DC TPDR ESB Sbj/Rd DRon TNicholson KGoller JUL 18 086 MEMORANDUM FOR: Leon L. Beratan, Chief Earth Sciences Branch, DRPES, RES FROM: Thomas J. Nicholson, ESB, DRPES, RES
SUBJECT:
TRIP REPORT ON INTRAVAL AD H0C MEETING, STOCKHOLM AND .
VISIT TO ATOMIC ENERGY RESEARCH ESTABLISHMENT'S HARWELL LABORATORY, ENGLAND On April 13, 1986 I traveled to Stockholm, Sweden to attend an INTRAVAL ad hoc meeting. While in Stockholm, I met with Swedish Nuclear Power Irspectorate (SKI) officials. They accompanied me on a field visit to the Forsmark site where the final Swedish repository for low-level and intermediate-level waste from nuclear power reactors (SFR) is under construction. I also discussed the previous INTRAC0IN and HYDROCOIN efforts with Dr. Alf Larsson, SKI, the HYDRCCCIN and INTRACOI.1 chairran, and Dr. Kjell Andersson, SKI, my host and HYDROCOIN and INTRAC0IN secretary. The following discussions summarize the Forsmark site visit and the INTRAVAL ad hoc meeting proceedings.
Forsmark Site Visit Prior to the INTRAVAL meeting, I accompanied Dr. Kjell Andersson, SKI and Dr. Chin Fu-Tang, LBL to the Forsmark site. Enclosure 1 shows the SFR, which is located on the Baltic Sea to enable waste transport by ship. The waste burial strategy is to place the waste in excavated tunnels and silos beneath the sea floor to preclude radionuclide transport to fresh-water aquifers on land. The Swedish Nuclear Fuel and Waste Management Company (SKB) has the responsibility of siting, design, construction, and operation of the SFR facili ty.
Blasting work for the tunnel entrance at Forsmark began on August 19, 1983. Phase 1 of the underground construction is nearing completion and will be completed by 1988 (see Enclosure 2 for schedule). The testing and quality assurance program was in progress. Dr. Rolf Christiansson, an SKB contractor j in charge of the geologic mapping and fracture analysis program, led us through l the underground facility.
Enclosure 3 shows the design of the underground tunnels and silo which we n toured. The construction and operating tunnels are parallel and extend one m8$ kilometer froJ: the above-ground service buildings (under construction) to the ggn- storage caverns. Enclosure 4 shows a diagram of the silo repository which will os store most of the radioactive wastes. These wastes consist primarily of ion
$8 exchange resins solidified in concrete molds or metal drums. We toured the g recently excavated silo cavern (there will be 4 in all) which measures 70 i ho meters high and 30 meters in diameter. An inner concrete silo was under 88 construction within the cavern and will measure 50 meters high and 25 meters in Y
8 oE OFC: ESB:REJ- :ESB:RES[N :ESB:RES : : : :
ma.o __________ ___________________________________________________________________________
NAME:TNicholson :RKornasiewicz :LBeratan : : : :
l DATE:7/lf/86 :7/J8/86 :7/ /86 : : : :
2-diameter. The annulus space will be filled with a high cation-exchange clay with a specially designed rock drainage tunnel below to prevent ground-water accumulation and saturation. Rock pressure transducers and ground-water flux instruments are placed above and along the silo cavern face. We examined ground-water collection stations and monitoring recorders. This data which will be collected continuously during the Phase I and II construction work is an integral part of their performance program.
The siting requirements for the SFR facility are that the ground-water flow through the subsurface caverns and tunnels should be small. This implies that the ground-water permeabilities and gradients should be very low. The bedrock geology shown in enclosure 5 is dominated by granites of middle Precambrian age, (1700 - 1900 million years B.P.). Associated with the granites are dikes of amphibolites and younger pegmatites which intersect the crystalline rock mass and vary in size. The SFR site geology also has sequences of older supracrustal sediments which occurs as a large zone along the coastline (see Enclosure 5).
The tectonic setting is dominated by a large regional fault zone, called the Singo Line, which crosses the SFR access tunnels. The fault zone is about 200 meters wide and roughly parallels the coastline striking N50 W. Associated with the Singo Line are smaller steep fractured zones to the west and northwest of the SFR area. Dr. Christiansson showed us smaller partly-filled structures intersecting the storage area. The silo area has these smaller structures which are being actively monitored by rock stress transducers.
The joint frequency in the silo area is 3-5 joints per meter. Most of the joints, we observed, were filled. Dr. Christiansson stated that it appears that joints which strike northwesterly are sealed with a chlorite filling, and those that strike northeasterly have calcite and laumontite filling. At present there are nine boreholes used to measure rock stress. The major stress is horizontal and is oriented NW-SE. The rock stress in the silo cavern, the largest subsurface void, is 8-10 MPa.
l The ground-water gradient at the Forsmark site is estimated to be 0.5 m/km -
due to the very flat topography. No fresh water has been detected in the l underground excavations in the storage area which is approximately 2 kilometers i
off the coast of and 50 meters under the Baltic Sea. The ground-water flow system appears to have very low ground-water flow velocities since the water is more brackish then the overlying Baltic Seg. The regional hydrogeologic units have hydraulic conductivities of about 10~ m/s with the rock mass of the Singo Line fault zone being 10 times more conductive. The.Singo Line acts as a regional ground-water discharge zone which further reduces ground-water flow to the SFR area.. Hydraulic conductivity estimated from sycific fgx7 measureihents
'in the rock mass.of the sgorage area varies between :10 'to 10 m/s with the fracture zones having 10- m/s values.- The access tuiinels' are ' shotcreted .to reduce water infiltration and to help stabilize the' tunnel openings. We-observed the pneumatic devices applying the gunite to the newly excavated side tunnels. The silo area was not shotcreted since the total. ground-water flux e- -, n ,-----nm
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for the cavern is about 2 liters per minute indicating very low hydraulic conductivities.
The excavated tunnels and silo are very stable with rock stress values measured at 10 levels. The magnitude of the horizontal stress is 10 MPa in the NW-SE direction and 5 MPa in the NE-SW direction. The vertical stresses are equal to the weight of the overlying rock strata. The drill and blasting technique for the silo (a major engineering feat) consisted of four main steps (see Enclosure 6 for the drill and blasting sequences):
- 1. First the dome was excavated with coarse contours 2-3 m inside the final contour. During this work the extensometers for the roof were insta.ll ed. Finally the contour was blasted with help of handhold drilling.
- 2. Simultaneously a tunnel was excavated to the bottom of the silo.
- 3. From the dome a 50 meter deep shaft was drilled into the center of the silo. The blasting sequence was an upward-going spiral starting from the bottom. Only the fractures from the blasting were filled with explosives.
- 4. Benchesof6mheightwereblastedfromthegome. Loading was made from the bottom tunnel. A digger with 1.5 m bucket on the bench made the flow of rock through the shaft possible. Each blasted bench was lowered in steps of 2.m to make reinforcement work possible.
Extensometers were installed at different levels.
The SFR site visit ended with a technical discussion in SKB's offices at Forsmark where we went over the anticipated future work and performance assessment program. Measurements of rock stress, in-situ rock permeability, piezometric levels, and ground-water inflow; ground-water chemical sampling and geologiq, mapping were discussed.
INTRAVAL Ad Hoc Meeting On April 17-18, I attended the INTRAVAL ad hoc meeting held at the SKI offices in Stockholm. Enclosure 7 lists the participants who were invited by the SKI officials that are formulating the International project. The intended purpose of the INTRAVAL project is to study the problem area of validation of geosphere performance assessment models in a comprehensive and systematic manner. The meeting followed the SKI established agenda (see Enclosure 8).
l Dr. Andersson., SKI. presented a background discussion based upon his -
l January 16, .1986."INTRAVAL Project , Proposal" (see Enclosure 9). -He : felt that ~
the validity of different models' shou'ld be evaluate'd by com'parison between l model calculations and available: data from field and laboratory experiments and l
natural analogues. The majority of the presentations were specific proposals l
for field and laboratory experiments, and natural analogue studies to be considered for the INTRAVAL project. I expressed concern that a strategy i
4
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l should be developed first with specific recommendations on the proper acceptability criteria prior to discussing the specific proposals.
The INTRAVAL project differs from HYDROCOIN in that validation and uncertainty / sensitivity analysis will be of radionuclide transport models.
When the project work is near completion, ground-water flow models will be considered for incorporation.
Dr. Bertil Grunfelt, KEMAKTA-SKI, provided an overview of the INTRAC0IN project results on transport model assessment (see Enclosure 10). He attempted to show the connection to the INTRAVAL proposal and what lessons from INTRAC0lN needed to be addressed.
The main tasks of the INTRAVAL ad hoc group were envisioned by SKI as follows:
- 1. To give a brief review of present state of knowledge in the area of
. validation of.geosphere~ performance assessment.models with emphasis
^
on issuesJof special concern. , ,
c
- 2. To approach potential participants in the INTRAVAL ' project for investigating possible interest in the project and for gathering technical information for the work of the group.
- 3. To establish a general technical framework for the project.
- 4. To investigate potentially suitable experiments and natural analogues for use within INTRAVAL and to select a few cases for an initial phase of the project. For each selected case the objectives and requested modelling efforts should be specified.
- 5. To establish an organizational framework for INTRAVAL if the contacts with potential participants indicate that a reevaluation of the project seems probable.
The second and final meeting of the ad hoc group will be in Harwell, l England, November 5-7, 1986 to review the draft report presently in preparation l by ad hoc members and to accept proposals for use as test cases. A tentative outline of the draft report was presented by Dr. Kjell Andersson, SKI and modified according to consensus during the open discussion (see Enclosure 11).
Because of my presentation (see Enclosure 12) that dwelled on modeling I strategies, I was asked to help write the following draft sections: 1.
Introduction; 3.1 General Discussion of the. Process of Model . Validation; 7.1 Obje'ctives of INTRAVAL Proposal . Projects;Jand pro' vide comments on. 2.0 The Process of Performance Assessment.
The geologic media considered were fractured granite (Swedish, French, and Swiss proposals), salt formations (U.S., and German interest), unsaturated porous media (U.S. interest), and clay (U.K. interest). The following
discussion is a synopsis of the formal proposal presentations (see Enclosures 13-20).
- 1. Peter Hufschmied (NAGRA - Switzerland) (Enclosures 13 and 14)
Dr. Hufschmied presented a proposal "For a Synthetic Migration Experiment with the Purpose of Studying Validation Strategies for Geosphere Performance Assessment Models." His principal objective in proposing a synthetic ]
experiment was to overcome the "information uncertainty" which was identified in the INTRAC0lN Levels 2 and 3 report. He stated that the major problem with the ambiguous validation of geosphere transport models seemed to be the incomplete information due to the spatial and temporal variability of the physico-chemica.1 processes in a mathematical sense.
The development of the synthetic experiment would be through joint modeler and experimentalist collaboration. The highly detailed synthetic experiment would then serve as a tool for developing validation strategies by simulating
,various transport and flow problems from selected. data bases.. . Of.all the
. processes tof be incorporated in the ' syn'theti.c experiment', I felt the greatest '
need for special attention-were: sorption at' fractures surfaces, matrix diffusion, and' sorption in the matrix. The large.so'phisticated models will create the " observed" data to derive the bulk mean properties for the simplistic 1 and 2-dimensional nicdels. Predictions by the research codes would be compared with the synthetic experiment data for performance assessments.
The research codes envisioned to be used are 2-dimensional transport codes with matrix diffusion and sorption. The 3-dimensional codes considered were NAMSOL, SWIFT, PORFLO, and METIS.
- 2. Jong Hadermann (NAGRA/EIR - Switzerland) (Enclosures 15 and 16)
Dr. Hadermann presented a proposal on " Transport of Uranium Through Bored Cores from Crystalline Rock." The proposal was to use small-scale laboratory infiltration experiments for validation of radionuclide transport mechanisms in fractured rock (e.g. granite). The rock samples would be from the Grimsel and Bottstein sites. Uranium (VI) would be injected with water into one side of the granite block under simulated 1ithostatic pressures. Alpha-auto radiography pictures of the rock slice surfaces would be.made to detennine the transport pathway and rate. For comparison purposes, Uranium (VI) sorption distribution ratios would be derived from crushed rock materials. Basic hydraulic and mineralogic properties would be derived for each rock sample l prior to the injection tracer test. Performance assessment would be based upon l comparison of the model simulation results for tracer transport versus the observed tracer data.
- 3. Philippe Raimbault (CEA/IPSN-France) (Enclosures 17-and 18).-
Dr. Raimbault, CEA presented a proposal on " Risk Assessment Code Evaluation In France". The most interesting aspect of the proposal was the emphasis on developing a proper strategy for INTRAVAL that consisted of the following tasks:
(1) Identify appropriate experimental studies for several levels of validation assessments (e.g., simple flow systems, non-sorbing species) and different media (e.g., single fractures or homogeneous process medium);
(2) Increase the complexity of the test case progressively; (3) For each phenomena, study important time and spatial scale effects; (4) For more complicated hydrogeologic systems, perform first a complete ground-water flow modeling study; and (5) Examine coupled processes to include thermal affects and radionuclide migration.with brine.
The two in-situ tracer experiments in France which were proposed for the INTRAVAL project were: (1) Le Mayet de Montagne, and (2) Fanay-Augeres mine.
- a. Le Mayet de.Montagne Experiment ,
. Enclosure 17 -is a'_ technical' pa'per by Dr. Pierre:Toulhoat (CEA/IRDI .
France) on the " Experimentation and Modeling of U, Th,~and Lanthanides~
Transport in Fissured Rocks - Influence of Complexation". The aim of the experiments was to understand the coupling of mass transfer and solution-solid interactions using lanthanides and associated elements (U and Th) as tracers.
The three tracer experiments were conducted in a two borehole setup where the boreholes penetrated granite and had been hydrofractured. The specific tracers included uranyl carbonate, and Th, La, Sm, Eu, Dy and Yb-EDTA complexes.
t Recovery curves for the tracers were analyzed to study breakthroughs and to i differentiate between reversible and nonreversible sorption.
Their results stressed the importance of complexation, both in solution and on solid surface and its main consequences: when the tracer is complexed in order to be stabilized in solution, non linear sorption laws govern interactions, having important consequences upon the interpretation of tracing
- experiments. A major conclusion was that in some cases, the complex can I interact itself with the substrate,. modifying sorption laws, and possibly the reversibility.of sorption reactions. This study of long-lived radionuclides' behavior in geologic formations provides an
- excellent proposal for in-situ ~
experimentations, along with tracing experiments. The proposal is to study solution and surfaces complexes in order to explain recovery curves, and further, to predict long-term sorption properties of radionuclides. The work was started in 1982 and should be completed by the end of 1986.
l
- b. Fanay-Augeres Experiment The other proposed field experiment was the CEA work at the Fanay-Augeres mine (which Paul Davis, SNL and I visited south of Limoges, France in November 1985). The site is a formerly developed uranium mine in a large regional granite batholith. The hydrogeology is fairly complex. The tests will involve injection of tracers into intervals of horizontal boreholes that have been
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isolated by packers. The recovery of the tracers will be in the drifts. The tracers that are being considered are Iodine, EDTA complexed Cr, and Zr, and Rhodamine dye. The work began Fall 1985 and is to be completed in 1986. The injection tracer tests at Fanay-Augeres are open to INTRAVAL suggestions. The proposal is to study transport in fractured granite.
- 4. PeterAndersson(SwedishGeologicalSurvey)(Enclosure 19)
Dr. Andersson discussed previous fracture injection tests in Sweden. The work at Studsvik (see Enclosure 1 for location) covered the time period 1977 to 1983. The testing consisted of tracer tests in boreholes drilled in crystalline rock. The first tests were in boreholes 51 and 22 meters apart, and the second tests were in boreholes 12, 15, and 23 meters apart. The ground-water flow analysis involved solving radial convergent flow problems, and the transport analysis was for both sorbing and non-sorbing radionuclides (e.g.,Sr-85,Br-82,Na-24,Se-75,Tc-99,Sn-113,I-131,Cs-131,Nd-147. The comparison between theoretical breakthrough curves (concentration versus time) and plotted experimental points was extremely good for Sr-85 and Br-82. The analysis of data is still ongoing. -
For the Finnsjon field research area, located due west of Forsmark, (see Enclosure 1 for location) the tracer tests were for both instantaneous and continuousinjectiontechniquesfor(1)Rhodeminey{thNO,_(2)Rhodeminewith I , (3) Br and N0, (4) Cr-EDTA and I , and (5) Sr and I . The breakthrough
, curves were presented. The ground-water flow analysis was for convergent flow on the scale of 30 meters. This work has already been used in the INTRAC0IN project, and is documented in the final INTRAC0lN report.
The third project discussed was the STRIPA study (Enclosure 1 for location). The STRIPA site is located near an old iron ore mine. Adjacent to the ore excavations is a granite intrusion which is directly accessible at a level of 350 meters below land surface. The site was used for an NEA-cooperative research study on fracture flow. LBL and SKB scientists conducted the investigations. There has been much published on this site and the project, esp 9cially by Lawrence Berkeley Laboratory (Witherspoon and l Degerman,1978) l The SKB research has the objectives of studying methods and techniques for:
- detection and characterization of fracture zones,
- radionuclide migration and ground-water characteristics, and
- behavior of bentonite clay as backfilling and seeding material.
1 Witherspoon, P.A., LBL an'd 0. Degerman, SKB, "Swedish-American Cooperative Program on Radioactive Waste Storage in Mined Caverns-Program Summary",
LBL-7049, May 1978, Berkeley, California.
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The three specific projects at STRIPA that were discussed were: (1) tracer tests in a well cluster, (2) a 2-dimensional tracer experiment, and (3) a 3-dimensional tracer experiment. The well cluster experiment consists of a central injection hole surrounded by 15 detection holes. The ground-water flow is divergent from the central injection well to the encircling and symmetrically spaced detection holes 1.5 meters away. Hydraulic conductivity values were derived for discrete 1 meter packed-off interygls in the boreholes.
The hydraulic conductivity values ranged from 10- to 10- m/s. Following the hydraulic tests, tracers were injected into the central injection well.
Long-term (in excess of 250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />) monitoring in the surrounding detection wells produced in-situ data for comparison to analytical breakthrough curves.
The two additional studies discussed were an experiment of 2-dimensional channeling phenomena (flow through discrete fractures), and a 3-dimensional study of uneven flow and tracer distribution on a much larger scale (75 x 25 x 25 meters). The Swedish Geological Survey is conducting these studies and is willing to allow active INTRAC0IN involvement. The objective of the 3-D study is to get an understanding of the spatial distribution of ground-water pathways in crystalline rock over a long distance (up to 50m).
- 5. Ivars Neretnieks (Swedish Royal Institute of Technology - SKB)
Dr. Nerethieks presented a proposal to examine large-scale fracture flow in crystalline rock. The presentaticn was similar to his paper entitled
" Channeling, Matrix Diffusion, and Redox Capacity in Crystalline Rock - Some Questions in Connection with the Geologic Barrier" that he gave at the HYDROCOIN Symposium in Albuquerque, New Mexico, May 1985 (NUREG/CP-0079). The proposal dealt with a combined flow and tracer transport study in fractured crystalline rock on a scale of tens of meters in an excavated tunnel. The emphasis will be on studying matrix diffusion and its effect on radionuclide retardation. A series of telescoping holes into the granite rock mass would be used to determine (1) the natural stress field (2) the net ground-water flux (3) sample ground-water chemistry and (4) provide access for tracer sampling.
Specific tracer tests are still in the design phase and could be subject to a INTRAVAL workshop.
- 6. David Lever (U.K. DOE /Harwell) (Enclosure 20)
Dr. Lever presented an overview of two natural analogue studies for consideration as INTRAVAL projects:
(1) Koongarra Study (Australia)
The Koongarra study in Australia has been supported by the Australian Atomic Energy Commission and NRC's office. of Nuclear Regulatory Research.
The Koongarra site is ~a larg'e uranium ore body; of the East Alligator River area .on the north coastline of the Northern Territory. The ground-water flow system is characterized as having recharge along a major fault line.
The irregularly shaped ore body lies within both a weathered and unweathered zone.
l l
l
_g. e' The data collected in boreholes which dissect the natural ore body consist
. of the concentration of uranium and its daughter products in both rock specimens and the ground water. The work was to determine sorption values using laboratory and field estimates of uranium isotopes. Lead concentrations and relative abundance of lead isotopes were also collected as a way of detemining relative rates of migration, and the time uranium had been mobilized. The use of flow and transport modeling to examine the perfonnance of the natural ore body will be attempted and would be the basis for an INTRAVAL proposal.
I j (2) Brazilian Natural Ore Body (Pocos de Caldas Region, Minas Gerais, Brazil)
Dr. Lever . presented a much briefer discussion of another international cooperative study still under consideration. The study would involve examination of an open-pit uranium mine face. A redox-front phenomena is supposedly apparent in the mine face. Numerous rock corings and ground-water samples would be obtained and analyzed to study the redox front and determine the transport mechanisms and rate for the ore body.
After the formal proposals were presented, Dr. William Lee, Universit'y of California at Berkeley-D0E, presented an overview of DOE's performance assessment prcgram (Enclosure 21). His discussions centered on programatic aspects and the various contractor-D0E interplay. I presented a general discussion of topics to be considered in developing a performance strategy for INTRAVAL (see Enclosure 12). Following my presentations, I answered questions from Peter Hufschmied, NAGRA, and others which centered on the possibility of an unsaturated flow and transport proposal.
On April 18, 1986, Dr. Chin Fu-Tsang, Lawrence Berkeley Laboratory-SKI, presented an overview talk summarizing the ideas and discussion of the previous day plus his own ideas on performance modeling (see Enclosure 22). I felt his most interesting ideas were those adopted from a PNL paper by Steve Simmons and Charles Cole. His talk was general and did not go into technical specifics on experimental design nor hypothesis testing of performance modeling assumptions.
Harwell - British Geological Survey Meeting The following week I meet with scientists at the Atomic Energy Research Establishment's (AERE) Harwell Laboratory, Oxfordshire, England (see Enclosure 23 for attendee list). Dr. David Hodgkinson, AERE, who had met with me in Paris at the 4th HYDROCOIN Workshop and Coordination Meeting, had invited me to talk about NRC's research studies at West Valley.
His interest in West Valley was due to its similarity to the four
- candidate low-level (LLW) and short-lived intennediate-level waste (ILW) sites.
The four sites approved by the Nuclear Industry Radioactive Waste Eyecutive (NIREX) for site characterization are Elstow, Bradwell, Killingholme, and Fulbeck. All four sites were chosen based upon their geology (thick clay sequence), low population density, and low flooding potential. Of particular interest to the Harwell staff, was information on detennining hydraulic l
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properties of both weathered and unweathered fractured clay and the affect of organic solvents on altering the in-situ flow and transport properties. They were quite familiar with the West Valley site and wanted to know what had been learned.
The other aspects of site characterization for a clay site discussed were ground-water chemistry and age dating to be used in developing a performance model. We discussed the HYDROCOIN problems dealing with shallow-land disposal trenches and what information needed to be collected. The Harwell staff expressed a need to develop a site characterization plan with specific guidance to the NIREX contractors (Dames and Moore). I told them of NRC's Standard Format and Content Branch Technical position which had recently been issued.
Additional' disposal options of enhanced engineered trenches, tunnels, and above-ground bunkers were discussed. D0E's plans to build a tumulus LLW facility at West Valley was discussed, as was the Centre de la Manche facility.
The NAMMU, FEMWATER, and SUTRA codes were discussed as possible performance assessment models for simulating the engineered waste disposal facilities.
The' n1xt day -I m'eet with Dr. Neil C'hapman, British. Geologicalc5urvey (BGS), to discuss the~hydrogeologic aspects of the site selection for the four LLW sites under consideration. The site screening process involved a
" multi-attribute analysis" looking at (1) hydrogeologic flow conditions, namely travel times (2) geologic units present and their thicknesses, and (3) flooding potential involving quantitative analysis of flood levels and recurrence intervals.
I discussed the site characteristics of the four LLW candidate sites with Timothy McEwen, BGS. The Killingholme site sits on a glacial boulder clay of late Quarternary age (8,000 year B.P.). The Bradwell site sits on the London Clay (Eocene Age) which is a marine clay. The Fulbeck site sits on the Lower Lias Clay Formation (lower Jurassic Age) which is a marine clay with interbedded limestone. The Elstow site sits on the Oxford Clay, a middle Jurassic marine clay. The Bradwell site has in excess of 50 meters of clay, the Elstow site has a very thick clay unit, and the Fulbeck site has in excess of 120 meters of clay which are thick enough for either a tunnel or trench option. The Killingholme site has a relatively thin clay unit which may preclude the tunnel or trench options, which leaves the-tumulus option. Also,-
the glacial boulder clay overlies The Chalk Formation (a carbonate unit) which would preclude burial beneath the water tabic.
The hydrogeology of the sites were derived from literature searches, and limited test results from nearby government (i.e., Elstow site) or nuclear facilities (i.e., Bradwell site). The Oxford Clay at Harwell had been tested for hydraulic properties and geochemical sampling. This information was used for the Elstow site screening assessment. The Fulbeck site had no hydrogeologic nor geologic studies available. Therefore, historical records, including geologic maps produced in 1881 and local cultural history, and government records, were us;d.
.. .r.
For each site, a simplistic geologic and hydrogeologic system analysis was conducted to detennine the hydrogeologic units present, their hydraulic I properties, and the ground-water flow directions. The site characterization work is intended to assess these preliminary models and provide site specific input data for the performance models. For the site performance models, !
information on glacial and periglacial scenarios will need to be developed.
Therefore, methods to predict climatic and geomorphic changes are also being developed.
Present research on ground-water flow and transport in clay is being conducted by the BGS at the Drigg site. An in-situ tracer study using radionuclide including I-131 and Tc-99m has been performed for a radial flow field using multi-level piezeometers. Laboratory work on cores to determine KD's are used to determine break-through curves. The laboratory and field results compare favorably. The effects of natural organics (e.g., peat and vegetative matter) on solute transport need to be studied and used in their performance models.
w Thomas J. Nicholson Division of Programs and Earth Science; Earth Science Branch, RES cc: Without enclosures F. Costanzi, WMB, RES H. Schechter, IP R. Browning, WM, NMSS J. Cortez, RES P. Justus, WMGT, NMSS M. Knapp, WMCU, NMSS J. Greeves, WMEG, NMSS R. Kornasiewicz, ESB, RES E. O'Donnell, ESB, RES J. Stanner, WMLU, NMSS L. Rouse, FCAF, NMSS T. Clark, FCAF, NMSS J. Philip, ESB, NMSS N. Davison, FCAF, NMSS R. Codell, WMGT, NMSS