JPH0674412A - Method of washing sealed vessel - Google Patents

Abstract

PURPOSE: To reduce the cost required for removing a remaining solution in the same cleaning capability in a method wherein a closed container is cleaned with the cleaning solution introduced into the closed container or made in the closed container, more specifically in a cleaning method for a closed container, particularly a vaporizer wherein at least part of the cleaning solution remains in the closed container for the present after chemical or physical action to the closed container. CONSTITUTION: The interior of a closed container 1 is brought into temperature corresponding to at least boiling temperature of a cleaning solution L at pressure larger than external pressure and at the external pressure, and the closed container 1 is opened for a predetermined time in order to vaporize the cleaning solution L and hence a remaining solution R of the cleaning solution L with a reduced volume owing to vaporization is removed from the closed container 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of cleaning a closed container with a cleaning solution which is introduced into or made in the container, wherein at least a part of the cleaning solution is contained in the container. The present invention relates to a method for cleaning a closed container, particularly a steam generator, which is intended to remain inside the closed container after a chemical or physical action.

[0002]

2. Description of the Related Art A cleaning method of this type is known, for example, from European Patent No. 0273182. This method often cleans the secondary side of the steam generator, which is a structural part of a nuclear power plant or a typical thermal power plant. In the main step of the cleaning method, contaminants present in the container, such as iron oxide adhering to the wall of the container, are dissolved by the cleaning solution. The cleaning solution is enriched with pollutants after the main steps of the cleaning method. Furthermore, the chemical components necessary for cleaning are also components of the remaining cleaning solution.

Therefore, it is generally necessary to remove the used residual cleaning solution as secondary waste. It must be stored safely or made harmless in a special way.

Use expensive storage containers for this, or
Auxiliary expensive processing methods that require special equipment must be implemented.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for cleaning a closed container which can reduce the cost required for processing a residual solution with the same cleaning capacity.

[0006]

SUMMARY OF THE INVENTION According to the invention, the object of the invention is, in a cleaning method of the type mentioned at the beginning, that the interior of the closed container is at a pressure greater than the external pressure and at least at the boiling temperature of the cleaning solution at the external pressure. At the corresponding temperature, the closed container is opened for a certain time to evaporate the washing solution,
It is solved by removing the residual solution of the washing solution, which has been reduced in volume by evaporation, from the closed container.

[0007]

In the present invention, the evaporation does not belong to the original cleaning step and is performed only when the cleaning is almost completed. Evaporation reduces the residual volume of wash solution after the original wash.

The boiling step of the cleaning solution is started by the pressure drop in the container after opening the container, provided that the temperature in the container is equal to or higher than the boiling temperature of the cleaning solution at the external pressure. . In that case, the water vapor first flows into the gas chamber in the container. This water vapor then exits the vessel through the opening. Evaporation reduces the volume of the wash solution. The residual solution contains a high concentration of chemically or physically dissociated material. By significantly reducing the volume of residual solution, storage space is advantageously saved without having to employ expensive chemical treatment methods. The residual solution removed from the container can be subjected to additional treatment.

The method according to the invention also has the advantage that the cleaning solution remaining after the original cleaning is evaporated directly in the container. In that case, the solution does not have to be transferred to another facility. Advantageously, no energy input is generally required to evaporate the wash solution to reduce its volume. The residual heat from the preceding washing step is sufficient to cause the boiling step and the consequent evaporation, without the introduction of heat after opening the vessel and without pressure introduction.

When the evaporator is intended as a closed container to be cleaned, for example at least one valve originally present for evaporation is opened for a certain time. This valve is, for example, a main steam discharge valve. This has the advantage that the volume of residual solution that needs to be processed is significantly reduced by existing equipment.

The method according to the invention has the advantage that, at low cost, the residual solution required for the treatment of the cleaning solution is reduced significantly directly in the container without the introduction of energy. Therefore, there is less storage space for residual solution, and no expensive additional equipment is required to carry out the method of the invention.

[0012]

The method according to the invention will now be described in detail with reference to the drawings.

The cleaning of the steam generator 1 is carried out by means of a cleaning solution L which is introduced or is generated in the steam generator 1.
After such a known cleaning process, the cleaning solution L remains in the steam generator 1. The solution L also contains a chemically or physically dissociated contaminant such as a metal oxide. Therefore, after the main cleaning step, the steam generator 1 is filled to almost half with the solution L which is no longer needed.
This solution L must be removed. At this point of time, the steam generator 1 is under a pressure higher than the external pressure. The external pressure is the pressure around the steam generator 1. Further, the temperature inside the steam generator 1 is equal to or higher than the boiling temperature of the solution L. This is due to the requirements of the preceding cleaning step.

The method according to the invention can be carried out directly in the steam generator 1. Solution L is first steam generator 1
There is no need for expensive auxiliary equipment such as a separate evaporator, which has to be refilled into it. The method according to the invention therefore proposes that the main steam release valve in the connecting pipe 2 in the upper part of the steam generator 1 be opened for a certain time. This releases the pressure inside the steam generator 1,
This causes a boiling phenomenon of the cleaning solution L without the introduction of energy. This boiling phenomenon produces water vapor D, which first rises into the gas chamber 1a of the steam generator 1 and exits the steam generator 1 through an open main steam release valve. This evaporation reduces the volume of the solution L. The liquid level of solution L drops from fill level 3 to fill level 4.

The volume of the residual solution R of the solution L that remains after the disappearance of water vapor is so small that the required storage space is extremely small, which significantly enhances the economical efficiency of the entire cleaning method. In addition, when the residual solution R is to be reprocessed, the small volume thereof causes high economic efficiency.
When the residual solution R is to be hardened, not only the storage space thereof is reduced, but also a small amount of solidified material can be used.

[0016]

The method according to the invention is simple to implement,
The economical efficiency of the method for cleaning the closed container, especially the steam generator 1, can be improved.

[Brief description of drawings]

1 is a cross-sectional view of a steam generator partially filled with cleaning solution.

[Explanation of symbols]

 1 steam generator 1a gas chamber of steam generator 2 connecting pipe for main steam release valve 3 filling level before evaporation 4 filling level after evaporation L cleaning solution D steam R residual solution

Claims (2)

[Claims] 1. A method of cleaning a closed container (1) with a cleaning solution (L) which is introduced into or produced in the closed container (1), wherein at least part of the cleaning solution (L) In the method for cleaning a hermetically sealed container (1) for the time being after the chemical or physical action on the hermetically sealed container (1), the inside of the hermetically sealed container (1) has a pressure larger than an external pressure. The washing solution (L) is brought to a temperature corresponding to at least the boiling temperature of the washing solution (L) at an external pressure, and the closed container (1) is opened for a certain period of time to evaporate the washing solution (L), and the washing solution (L) reduced in volume by evaporation. The method for cleaning an airtight container, characterized in that the residual solution (R) of 1) is removed from the airtight container (1). 2. Method according to claim 1, characterized in that at least one main steam release valve is opened for a certain time in order to vaporize the cleaning solution (L) in the steam generator (1).