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Title: Direct disposal of spent fuel in rock salt: Geomechanical effects and gas release

Abstract

At the Asse salt mine in Germany a test field has been operating since September 1990 for the purpose of demonstrating the practicability of the direct disposal of spent fuel elements in drifts. According to the concept for direct disposal of spent fuel, disposal casks called Pollux will be emplaced on the floor of the drifts backfilled with salt afterwards. The main objectives of this test are studies on the thermal and thermomechanical effects in the backfilled drifts and in the surrounding rock due to the power output of the spent fuel in the casks. The temperatures at the surface of the electrically heated mock-ups of the Pollux-casks increased up to 210 C after five months and then gradually decrease. Determinations of the initial stress state in the test field were carried out by overcoming and slot cutting techniques before the test drifts were opened. After the beginning of heating the casks, the rock stresses increased rapidly related to the temperature at the specific location and later on decreased slowly. Deformation measurements are performed in the host rock using multi-point extensometers and closure gauges for measuring the closure of the test drifts in the heated as well as in themore » unheated areas. Specially designed equipment was used to observe the settling of the backfill. In the period of about 4 years, the convergence of the backfilled drifts accelerated enormously and caused backfill pressures up to 1.8 MPa. The concentrations of the main components carbon dioxide, hydrogen, and methane in the pore volume of the backfill were analyzed.« less

Authors:
; ;  [1];  [2]
  1. Forschungszentrum fuer Umwelt und Gesundheit GmbH, Braunschweig (Germany). Inst. fuer Tieflagerung
  2. Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany)
Publication Date:
OSTI Identifier:
182957
Report Number(s):
CONF-950917-
ISBN 0-7918-1219-7; TRN: IM9608%%326
Resource Type:
Book
Resource Relation:
Conference: 5. international conference on radioactive waste management and environmental remediation, Berlin (Germany), 3-9 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Fifth international conference on radioactive waste management and environmental remediation -- ICEM `95: Proceedings. Volume 1: Cross-cutting issues and management of high-level waste and spent fuel; Slate, S.; Feizollahi, F.; Creer, J. [eds.]; PB: 900 p.
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; SALT DEPOSITS; RADIOACTIVE WASTE DISPOSAL; FEDERAL REPUBLIC OF GERMANY; RADIOACTIVE WASTE FACILITIES; SPENT FUELS; UNDERGROUND DISPOSAL; PERFORMANCE TESTING; THERMAL ANALYSIS; STRESS ANALYSIS; EXPERIMENTAL DATA; SPENT FUEL CASKS; BACKFILLING; ROCK MECHANICS; RESERVOIR PRESSURE; RADIOLYSIS; TEST FACILITIES; RESERVOIR TEMPERATURE; STRATA MOVEMENT; BULK DENSITY

Citation Formats

Gommlich, G., Jockwer, N., Schneefuss, J., and Heusermann, S.. Direct disposal of spent fuel in rock salt: Geomechanical effects and gas release. United States: N. p., 1995. Web.
Gommlich, G., Jockwer, N., Schneefuss, J., & Heusermann, S.. Direct disposal of spent fuel in rock salt: Geomechanical effects and gas release. United States.
Gommlich, G., Jockwer, N., Schneefuss, J., and Heusermann, S.. Sun . "Direct disposal of spent fuel in rock salt: Geomechanical effects and gas release". United States. doi:.
@article{osti_182957,
title = {Direct disposal of spent fuel in rock salt: Geomechanical effects and gas release},
author = {Gommlich, G. and Jockwer, N. and Schneefuss, J. and Heusermann, S.},
abstractNote = {At the Asse salt mine in Germany a test field has been operating since September 1990 for the purpose of demonstrating the practicability of the direct disposal of spent fuel elements in drifts. According to the concept for direct disposal of spent fuel, disposal casks called Pollux will be emplaced on the floor of the drifts backfilled with salt afterwards. The main objectives of this test are studies on the thermal and thermomechanical effects in the backfilled drifts and in the surrounding rock due to the power output of the spent fuel in the casks. The temperatures at the surface of the electrically heated mock-ups of the Pollux-casks increased up to 210 C after five months and then gradually decrease. Determinations of the initial stress state in the test field were carried out by overcoming and slot cutting techniques before the test drifts were opened. After the beginning of heating the casks, the rock stresses increased rapidly related to the temperature at the specific location and later on decreased slowly. Deformation measurements are performed in the host rock using multi-point extensometers and closure gauges for measuring the closure of the test drifts in the heated as well as in the unheated areas. Specially designed equipment was used to observe the settling of the backfill. In the period of about 4 years, the convergence of the backfilled drifts accelerated enormously and caused backfill pressures up to 1.8 MPa. The concentrations of the main components carbon dioxide, hydrogen, and methane in the pore volume of the backfill were analyzed.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 1995},
month = {Sun Dec 31 00:00:00 EST 1995}
}

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  • Disposal of high-level radioactive waste in Germany is planned to take place in deep salt repositories. Direct disposal of spent fuel is taken into account as well as disposal of reprocessed high-level waste. Borehole and drift emplacement techniques are considered for both HLW and spent fuel. The following disposal concepts are taken into account: pure borehole emplacement with waste in steel drums or canisters, pure drift emplacement with waste in Pollux casks, and combined drift and borehole emplacement. Each of these concepts was investigated for different ratios of waste from direct disposal and from reprocessing. Long term safety assessments weremore » performed with scenarios of brine intrusion via possible anhydrite veins and from brine pockets in the surrounding salt rock. A survey of the disposal concepts as well as the models used by the computer code for long term safety assessment will be presented. The safety assessments investigated the influence of the geometrical layout of the emplacement sites, the layout temperature of the entire repository and the different behavior of spent fuel and reprocessed waste. The calculations were performed both deterministic and probabilistic. The deterministic calculations were performed with best estimate values of the input parameters and in some variants with locally varied values of selected parameters.« less
  • This work examines the key issues affecting direct disposal of spent nuclear fuel without reprocessing, an option which certain countries now pursue either for economic reasons or to avoid dependence on foreign back-end services. The book provides a discussion of a subject of concern to nuclear waste disposal engineers and environmentalists.
  • An analysis of the current status of technologies and issues in the major portions of the back-end of the nuclear fuel cycle is presented. The discussion on nuclear fuel reprocessing covers the reprocessing requirement, reprocessing technology assessment, technology for operation of reprocessing plants, and approval of reprocessing plants. The chapter devoted to spent fuel storage covers the spent fuel storge problem, the legislative response, options for maintaining full core discharge capacity, prospective availability of alterntive storage options, and the outlook for California. The existence of a demonstrated, developed high-level waste disposal technology is reviewed. Recommendations for Federal programs on high-levelmore » waste disposal are made.« less
  • This paper describes the reference concept for the disposal of heat generating radioactive waste in Germany. It also highlights a new approach to reduce efforts for the transport and handling of waste canisters by introducing a new canister type for spent fuel (BSK 3). The objectives and the scope of a corresponding research and development program performed in the context of the 6. European Framework Program will be presented. The entire emplacement process and the technical components will be described and illustrated. The program for the corresponding 1:1-scale demonstration tests and the location of the test site will be explained.more » Eventually, an outlook on the planned demonstration test will be given. (authors)« less
  • Dissolution of spent fuel has been studied in saline, anaerobe, carbonate free solutions. Processes controlling spent fuel dissolution and associated radionuclide release are radiolytically controlled oxidative dissolution, sorption on container, solubility and coprecipitation. Upper limits for oxidative dissolution rates are given by the production rates of oxidative radiolysis products. This limitation leads to a strong decrease in surface area normalized reaction rates with increasing surface to volume ratio (S/V) and imposes geometric constraints on prediction of spent fuel behavior in a repository. Solution concentrations of Am during spent fuel corrosion were about 5 orders of magnitude lower than the solubilitymore » of Am(OH){sub 3}(s) and are likely controlled by coprecipitation. Pu concentrations may be controlled by Pu(VI) or Pu(IV) (hydr)oxides.« less