SYNOPSIS:

CLAB is the first licensed underground storage of spent nuclear fuel in the western world. The storage consists of water-filled pools constructed in a 117 m long and 27 m high cavern with a span of 21 m. The cavern is situated in granitic vulcanite 30 m below ground surface. Site investigations, design and construction are described. Extensive reinforcements and rock support were carried out. To ensure rock stability a thorough control program was undertaken.

RESUME:

Le CLAB est la première installation souterraine agreee dans le monde occidental pour le stockage de combustible nucleaire use. Cette installation se compose de bassins remplis d'eau, creuses dans une grotte longue de 117 m et haute de 27 m dont la voûte a une portee de 21 m. La grotte en question est situee dans une volcanite acide à 30 m au-dessous du niveau du sol. On decrit les phases de prospection geologique et de construction. La roche a fait l'objet d'importants renforcements et, pour assurer un maximum de tenue à l'ensemble, un programme de contrôle minutieux a ete realise.

ZUSAMMENFASSUNG:

CLAB ist die erste zugelassene unterirdische Verwahrungsweise fuer verbrauchten Kernbrennstoff im Westen. Die Verwahrung erfolgt in Wasserbecken, die in eine 117 m lange und 27 m hohe Kaverne von 21 m Breite eingebaut sind. Die Kaverne liegt in einem granitartigen Tiefengestein 30 m unter der Erdoberflache. Die Untersuchungen an Ort und Stelle, der Entwurf und die Bauausfuehrung werden beschrieben. Umfangreicher Ausbau wurde ausgefuehrt. Zur Sicherung der Standfestigkeit des Gebirges wird ein sorgfaltiges Kontrollprogramm durchgefuehrt.

INTRODUCTION

An intermediate storage for spent nuclear fuel - CLAB - is in the final stage of completion in southeastern Sweden. The underground storage is located in hard crystalline bedrock adjacent to the nuclear power plant Simpevarp. Spent fuel will be received from this plant and from Ring- hals, Barseback and Forsmark. The storage capacity is about 3000 tons of uranium. The fuel will be stored in the cavern until the final deposition when it is reprocessed or deposit without reprocessing, Gustavsson et al., 1980. The storage is owned by the Swedish Nuclear Fuel Supply Company (SKBF). OKG Aktiebolag (OKG) is responsible for the overall project management and construction work. The obligation of the civil engineering design is held by the Swedish State Power Board (SSPB). The contractor is a consortium comprising of ABV, Skånska Cement Cementgjuteriet AB and WP-System AB. The Swedish Nuclear Power Inspectorate (SKI) possesses the control of the storage for the Swedish Government. A general description of CLAB is given by Gustavsson et al., 1980. This paper discusses the realization phase of the storage from the site investigation to the completion of the underground chamber.

2. LAY-OUT OF THE STORAGE FACILITIES CLAB

storage facilities comprise three main units on the ground, namely fuel reception, auxiliaries and office, Fig.1. The storage chamber is connected to the fuel reception by a fuel shaft and a service shaft. The cavern has the dimension 117 m in length, 27 m in heigth and a span of 21 m. Fig. 2. The cavern contains four water-filled pools for storage of spent fuel and one central pool. The pools are of concrete with an inside cover of stain- less steel. A transept, 70 m in length, is located perpendicular to the long axis of the cavern. This enables an expansion of the storage capacity in the future, Fig. 4.

3 SECURITY REQUIREMENTS

The fuel will be stored in water-filled pools in the cavern. Extensive security is required in order to protect the fuel against any mechanical damage or outside forces.

3.1. Seismicity and ground movements

The cavern and the pool are designed and constructed to resist an earthquake which generates a ground acceleration of 0.1 g. CLAB is located in an area of Fennoscandia, which is characterized by very low seismicity, Kulhanek and Wahlström, 1977. The rate of glacial uplift in the area is of the order of 2 mm/year.

3.2 Stability of the cavern

The requirements for the stability of roof and walls of the cavern is extremely high as no rock burst, rock falls or collapse are allowed. Therefore the site investigation for location and orientation of the cavern in relation to tectonic structures has been more through than is normal for caverns in crystalline bedrock. Both the transport tunnel and cavern have been mapped in detail during the excavation phase in order to analyses the rock structures and stability. The displacement of both walls and roof have been measured. Theoretical calculations of stresses and deformations were performed using a two dimensional linear elastic finite element model. Larger safety factors then normally is required in this type of rock has been used. Smooth blasting and contour blasting has minimized the damage of the rock mass. The rock support consists of systematic rock bolting and shotcrete lining.

This content is only available via PDF.
You can access this article if you purchase or spend a download.