DOUNREAYILW SHAFT: INTEGRITY OF THE STUB TUNNEL PLUG

The nuclear industry in the UK has its origins in the 1950's, when much of the infrastructure was built in support of nuclear research programmes, civilian power stations and defence programmes. The UKAEA site at Dounreay in the north of Scotland was a key experimental site in the development of nuclear technology in the UK. This paper describes the process of estimating the condition and physical properties of a mass concrete plug, located in an inaccessible water filled tunnel some 60 metres below ground, at the Dounreay site. The Plug provides a containment barrier for intermediate level waste (ILW) stored in an adjacent shaft. When assessing old structures, engineers often have to work with limited data and somehow transform this into a robust engineering substantiation. This is particularly the case in assessing aging structures against the requirements of a modern nuclear Safety Case. In this paper the thought processes of the Engineer are illustrated in the approach used to build a picture of the mass concrete plug, utilising the original design criteria, evidence from construction records, scoping calculations and engineering judgement.

• INTRODUCTION

• DESCRIPTION OF THE SHAFT AND PLUG

• ENGINEERING SUBSTANTIATION – WHAT DO WE WANT TO KNOW?

• WHAT DO WE KNOW?

• WHAT CAN WE REASONABLY ASSUME/DEDUCE?

• DECOMMISSIONING STRATEGY

• CONCLUSIONS

• REFERENCES