GB2271016A

GB2271016A - Method of and apparatus for decontamination of a contaminated substance

Info

Publication number: GB2271016A
Application number: GB9219001A
Authority: GB
Inventors: David Saul; John Charles Bennett
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1992-09-08
Filing date: 1992-09-08
Publication date: 1994-03-30
Also published as: GB9219001D0

Abstract

Silica gel which has been contaminated by tritiated water is made reusable by driving off the water and then condensing it and collecting it in a vessel. The silica gel is heated in an oven 10 on trays 12, 14, 16 and the water vapour is passed over a platinum catalyst 24, cooled by condenser 25 collected in vessel 26, fitted with a silica gel absorber 30 in vent 28. <IMAGE>

Description

METHOD OF AND APPARATUS FOR DECONTAMINATION OF AN CONTAMINATED SUBSTANCE Some nuclear reactors are gas cooled in known manner. During its passage through the reactor it it sometimes necessary to condition the gas which results in the gas picking up water. Water can also be in the gas from other sources. The water is removed from the gas by a known means utilising silica gel which results in the silica gel becoming contaminated with tritium.

In some applications the level of contamination of the silica gel is above that to permit the authorised disposal route to be utilised.

The present invention seeks to provide both a method of and apparatus for treatment of contaminated silica gel so as to allow its disposal via the current authorised route, disposal of the separated tritium via an authorised route and/or possible re-use of the silica gel.

According to one aspect of the present invention a method of de-contaminating silica gel which has been contaminated with tritiated water comprises the steps of arranging the silica gel in spaced layers in an oven, heating the silica gel to drive off the tritiated water in the form of steam, condensing the steam and collecting the resulting tritiated water in a vessel.

According to a further aspect of the present invention decontaminating apparatus comprises in combination an oven, a fluid collection vessel, a conduit connecting the oven and vessel and steam condensing means connected to condense steam driven from the heated silica gel within the conduit at a position upstream of the vessel, so as to enable the collection of the resulting fluid in the collection vessel and a vent in said collection vessel, said vent comprising a silicon gel filter absorbing any steam not condensed.

The invention will now be described by way of example and with reference to the drawing.

In the present example it is assumed that a gas has been passed through a power station reactor in known manner, so as to transfer heat during generation.

The gas has become contaminated with tritiated water and in order to dry the gas prior to its recirculation in the reactor, it is passed through silica gel, which, as is known, has an affinity for water and absorbs to it without forming a new compound.

The silica gel removes the water from the gas, but is itself now contaminated. This can be to such an extent that it cannot be re-used in the system, nor can it be disposed of, via an authorised route. The invention therefore provides apparatus in the form of an oven 10 into which the contaminated silica gel is loaded, preferably in spaced layers 12, 14 and 16, this by way of example only. The oven is connected via a conduit 18 to a water collecting tank 26 and has a fan 22 connected for operation as described hereafter.

When the oven is loaded, heat is applied and the fan 22 started. The heat of about 1500C is sufficient to drive off the tritiated water in the form of vapour and the fan 22 generates a pressure which ensures that the vapour enters the conduit and continues to flow therethrough.

A non return valve 20 is provided in the conduit 18 near the inlet thereto.

In the present example, a chamber 22 is provided which contains a platinum catalyst 24. The purpose of the catalyst is to oxidise any tritium gas that may be present, converting it to tritiated water vapour. The catalyst however, may not be essential, and where that proves to be the case, it may be dispensed with.

The tritiated water vapour passes through a part of the conduit 18 which includes a condensing device 25 of any known, suitable form, where the vapour is condensed and what is then tritiated water passes to the holding tank 26.

The tank 26 has a vent 28 which includes a silica gel filter 30 which prevents any lingering vapour from escaping with displaced air. The silica gel in the oven 10 may be re-used or is now in a suitable form for disposal and the tritiated water in the tank 26 is in a form suitable for disposal via an authorised route.

Claims

Claims:

1. A method of de-contaminating silica gel which has been contaminated with tritiated water comprising the step of arranging the silica gel in spaced layers in an oven, heating the silica gel to drive off the tritiated water in the form of steam, condensing the steam and collecting the resulting tritiated water in a vessel.

2. Silica gel decontamination apparatus comprising in combination an oven, a fluid collection vessel, a conduit connecting the oven and vessel and steam condensing means connected to condense steam driven from the silica gel upstream of the collection vessel, so as to enable collection of the condensate therein, and vent means in the vessel comprising a silica gel filter.