PLANS FOR SODIUM RESIDUAL REMOVAL

The current plans for the residual sodium removal from the FFTF systems is a combination of in-situ treatment by superheated steam and component removal and subsequent treatment by superheated steam. The major sodium wetted components are listed below and selected components are discussed in detail, and are listed below:

— Reactor vessel;

— Primary and secondary piping and tanks;

— Small bore piping (~ 4 115 m);

— Small heat exchangers and electromagnetic pumps (~ 33 223 m of tubing);

— Small sodium valves (~ 330) (may need to cut apart);

— Secondary cold traps;

— Primary cold traps, cesium traps and vapor traps;

— Fuel Storage Facility (FSF) and Interim Decay Storage (IDS) vessels and contents;

— Dump heat exchanger tube bundles;

— Primary/secondary pumps;

— Intermediate heat exchanger tube bundles;

— Sodium reactor experiment and hallam sodium containers (from other reactors).

4.1. Reactor vessel

The reactor vessel estimated sodium residual hold-up is ~ 750 L. Unlike the closure programs of other liquid metal reactors, the FFTF reactor will not be disassembled following cleaning. The vessel will be flushed with water to assure maximum reaction of metallic sodium. The only disassembly currently planned is the raising or removal of the instrument trees to access the thermal baffle areas (see Fig. 4).

This is considered necessary because of a sleeve in the reactor head that segregates the head thermal baffles from the instrument tree thermal baffles.

4.2. Small bore piping, dump heat exchanger tube bundles, small heat exchangers, electromagnetic pumps and small valves

This group of components comprises a major portion of the sodium residual removal effort. These items and components will be removed from the plant and washed in an adjacent facility. The removal of the primary small bore piping will present the greatest challenge. The removal of each section of pipe will consist of:

— Appropriate planning and isolation;

— Sequential removal of stainless steel insulation cover, trace heat and thermocouples;

— Cutting and removal of pipe.

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This work must be done in a radiation area and with all of the protective measures required for working with inert gas and metallic sodium. A diagram of the Dump Heat Exchanger tube bundle is shown in Fig. 5.

4.3. Sodium traps

The photo and diagram of the secondary cold trap is shown below in Fig. 4. These traps are currently full of frozen sodium and still installed in the secondary system. The traps will be cut out of the system, removed to an adjacent facility, drained and cleaned.

Due to the radioactivity level of the primary cold trap and the cesium trap, those components will be treated at a separate facility. Drawings of these two components are shown in Figs 7 and 8, respectively.

FIG. 5. Dump heat exchanger tube bundle.

FIG. 6. Secondary cold trap.

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Primary cold trap:

Volume: 170/15 L (tank/economizer) Dose rate: 0.1-0.5 Sv/h

Location: Reactor containment Number: 1

FIG. 7. Primary cold trap.

Cesium cold trap:

Dose rate: ~ 0.5 Sv/h

FIG. 8. Cesium cold trap.

4.4. Spent fuel pools (IDS and FSF vessels)

Each of these two vessels contains significant residual volumes. The IDS vessel contains 112 fuel storage tubes that will contain ~ 10-15 L each. The FSF vessel contains 466 tubes that will retain ~ 5 L each in the bottom of each tube. Both vessels have an inner sleeve which may require the drilling of steam injection points through pressure vessel for residual removal. IDS and FSF are shown in Figs 9 and 10, respectively.

4.5. Intermediate heat exchanger (IHX) and primary pump

The intermediate heat exchanger (IHX) tube bundle and the primary pump (Fig. 11) are the two largest components that will be removed for cleaning. The tanks or shells of these components will remain in the reactor containment building for residual sodium cleaning. The components are shown below installed in the tanks.

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FIG. 9. IDS vessel. FIG. 10. FSF vessel.

FIG. 11. Intermediate heat exchanger (IHX) and primary pump.

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SUPERPHENIX – CREYS MALVILLE STRATEGY FOR DISMANTLING THE REACTOR BLOCK

E. JOULIA

ELECTRICITE DE FRANCE (EDF) – CIDEN, CREYS MALVILLE, FRANCE Abstract

This document describes the operations to be performed to dismantle the SPX reactor vessel. The first studies for dismantling the Superphenix power station reactor block have defined the broad outlines of the dismantling strategy and proposed a certain number of orientations. The period covers SPX reactor block dismantling, from the end of fuel unloading until complete dismantling of the installations. Two dismantling methods have been considered: Underwater dismantling (reference scenario); Dismantling with the structures covered with sodium carbonate (alternative scenario). In both cases, dismantling will be carried out ‘from the top’ through the reactor slab and will be preceded by a preliminary phase of sodium retention reduction followed by a phase of vessel internals carbonation. The dismantling studies are undertaken with a view to the work lasting eight years maximum. The work prior to reactor dismantling will last from the end of 2011, after sodium draining from the reactor, until the end of 2013. At present, the Superphenix dismantling work is planned to begin in 2014 and continue for a period of eight years. All the installations should have been dismantled by 2025.

1. INTRODUCTION

After a large scope of preliminary studies carried out from 1999 to 2002, two dismantling methods have been selected:

— Underwater dismantling (reference scenario);

— Dismantling with the structures covered with sodium carbonate (alternative scenario).

EDF made a choice based on the following principles:

— Anticipation of dismantling operations in order to facilitate reactor dismantling;

— Reduction of the risks as early as possible;

— Closest possible containment;

— Operations carried out on the basis of an ALARA approach.

2. DESCRIPTION OF DISMANTLING METHODS SELECTION