JPS5895299A - Nuclear power plant waste sludge removal equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a waste sludge removal device for a nuclear power plant,
In particular, the present invention relates to a nuclear power plant waste sludge removal device suitable for use in removing waste sludge contained in backwash water.

Generally, a steam turbine system or the like in a nuclear power plant is provided with a filter, and waste sludge collected in this filter is washed away with backwash water.

The backwash water containing waste sludge washed in this way is
After the waste sludge is removed by the waste sludge removal device, it is reused.

As a conventional waste sludge removal device of this type, there is one shown in FIG. The device shown in FIG. 1 includes a backwash water receiving tank 1, a backwash water transfer pump 2 whose suction side is connected to the F end of this tank 1, and a sedimentation separation tank 3 connected to the discharge side of this pump 2. A supernatant water transfer pump 6 whose suction side is connected to the supernatant water layer 4 in the upper part of the separation tank, a recovery tank 7 which is connected to the discharge side of this pump 6, and this tank 7.
A circulation pump 8 whose suction side is connected to the lower end of the pump 8, a circulation pipe 9 that connects the discharge side of this pump 8 and the upper end of the recovery tank 7, and a filter 10 interposed in the middle of this pipe 9. and a demineralizer 1 connected to the filtrate discharge side of the filter 10.
1.

In the apparatus configured as described above, backwash water is temporarily stored in a receiving tank 1 and transferred to a settling tank 3 by a pump 2. In this tank 3, the backwash water is left for a certain period of time and is separated into supernatant water 4 and waste sludge 5 by sedimentation. The settled waste sludge 5 is appropriately disposed of from the separation tank 3. Supernatant water obtained by separating the waste sludge 5 is transferred to a recovery tank 7 by a pump 6. While the water in the tank 7 is being circulated by the pump 8, it is filtered by a filter 10, and the low conductivity waste liquid filtered by the filter 10 is led to a demineralizer 11. The low conductivity pure water that has passed through the demineralizer 11 is reused as backwash water.

By the way, filters made of powdered resin have conventionally been installed in steam turbine systems of nuclear power plants. Cleaning and regeneration of this filter using backwash water was carried out at a frequency of 70 m3, once every 12 days, and at a water volume. In this case, the SS concentration in the backwash water is approximately 2500
ppm, most of the components of the waste sludge are powdered resin, and the cladding is 0.1 kg-crud/kg-po
It is wex.

When this backwash water with SS concentration is led to the sedimentation separation tank in the waste sludge removal equipment mentioned above and subjected to sedimentation separation, the allowable standard concentration for recovery into the recovery tank is 20pp in about 24 hours.
m or less.

In contrast, recently there has been a demand for the use of non-auxiliary filters such as electromagnetic filters. Washing regeneration with backwash water for this type of filter is approximately 20 m3
It will only take 110 days at a time. In this case, the SS concentration in the backwash water is about 2000 ppm, and most of the components of the waste sludge become crud.

However, since the particle size of waste sludge containing such components is very fine, it takes a long time to separate and remove even if it is led to the sedimentation tank and subjected to sedimentation separation, and the waste sludge is less than the recovery standard value of 20 ppm. It must be allowed to remain calm for a long period of time.

Therefore, during this period, backwash water cannot be received, and there is a fear that regeneration of the non-auxiliary material type filter using backwash water will be hindered.

Here, the change in SS# degree with respect to sedimentation time in the case of a powder resin filter and in the case of an electromagnetic filter, which is an example of a non-auxiliary filter, is shown in FIG. 2. As shown in Figure 2, the powder resin filter reaches the standard value of 20 ppm in about one day, while the SSa level decreases slowly due to the sedimentation of waste sludge when using backwash water for the electromagnetic filter. The standard value of 20 ppm is not reached even after 8 days have passed.

The purpose of this power generation is to extract SS from the sedimentation tank to reduce the SS concentration to below the recovery standard value, even if the sedimentation separation does not reach the recovery standard value, and then transfer it to the recovery tank. The purpose of the present invention is to provide a nuclear power plant waste sludge removal device that can be used to remove waste sludge.

The present invention includes 11, connecting a circulation pipe to the sedimentation separation tank, and providing a filter to this pipe, circulating the supernatant water of the sedimentation separation tank through the circulation pipe, and performing filtration with the filter during this circulation. The filtered water obtained through this process and having a reduced SS concentration is led to a recovery tank, while the supernatant water, which has a high SS concentration due to circulation filtration, is returned to the sedimentation separation tank for sedimentation. be.

The present invention will be described in detail below with reference to FIG.

FIG. 3 shows an embodiment of the present invention, and in FIG. 3, the same reference numerals as in FIG. 1 indicate the same parts as in FIG. 1. The backwash water receiving tank 1 has been abolished, and the backwash water is channeled directly into the sedimentation separation tank 3 from the top. A suction side of a pump 6 is connected to the separation tank 3 in correspondence with a layer formed by the supernatant water 4 in the tank, and a filter 13 is connected to the discharge side of the pump 6. A pipe 9 is connected to the primary side of the filter 13, and the pipe 9 is connected to the settling tank 3 by opening at the layer of supernatant water 4.

This piping 9 and the piping in which the pump 6 is interposed constitute a circulation piping in which supernatant water circulates. The secondary side of the filter 13 is substantially inserted into this circulation pipe, so that the supernatant water is circulated through the primary side of this filter. The secondary side of the filter 13 , that is, the side from which filtered water permeates through the filtration area from the negative side and seeps out, is connected to the recovery tank 7 .

Next, the effect will be explained.

For example, the electromagnetic filter is washed and regenerated, and the waste sludge adhering to the filter is washed away, and the back flood water containing the waste sludge flows directly into the sedimentation separation tank 3. In this tank 3, the backwash water is separated to some extent into waste sludge 5 and supernatant water 4 by sedimentation and separation. As mentioned above, the waste sludge from this backwash water has poor sedimentation properties, so the SSA level of the supernatant water will not reach the recovery standard value of 20 ppm unless a long period of time passes.
does not reach.

Therefore, in the waste sludge removal apparatus shown in FIG. 3, the pump 6 is operated to circulate the supernatant water 4 between the filter 13 and the upper layer of the separation tank 3 through the circulation pipe 9 while maintaining the water above the reference value. While this supernatant water circulates on the primary side of the filter 13, it permeates through the filtration area of the filter 13, and the filtered water seeps out to the secondary side. The SS concentration of this filtrate water is below the recovery standard concentration value of 20 ppffi.

This filtered water flows into the recovery tank 7 and is retained there.

On the other hand, the supernatant water circulating on the primary side of the filter 13 increases the SS concentration by the amount of the filtered water lost.

In other words, the supernatant water is circulated and concentrated.

This circulating and concentrated supernatant water is circulated and returned to the upper layer of the sedimentation separation tank 3. The waste sludge 5 in the returned supernatant water settles and is separated from the supernatant water before being sucked into the pump 6 again. In order to ensure sufficient settling time, the opening of the circulation pipe 9 is preferably spaced apart from the suction port of the pump 6 as much as possible. In addition, in order to effectively carry out this sedimentation action, a means for calming the inside of the sedimentation separation tank 3, such as a wave dissipating device, is provided.

It is recommended to install a laminar flow device, etc.

In addition, as mentioned above, as a filter that can obtain filtered water while circulating and concentrating supernatant water, there is, for example, a porous tube filter. When we conducted an experiment to obtain filtered water while circulating and concentrating supernatant water using this porous tube filter, we found that the processing capacity was o, tm3/hs, and the filtration area was 0.25.
m2, 8 pieces per plant, ssa of filtered water
We were able to reduce the temperature to below the maximum lppm.

According to this embodiment, even if the waste sludge does not settle sufficiently in the sedimentation separation tank and the SS concentration of the supernatant water does not reach the recovery standard value, filtered water can be obtained from the supernatant water and recovered. Can be supplied to the tank. Therefore, a sufficient amount of clean water to be used for the next backwashing operation can be secured in the recovery tank without depending on the sedimentation time in the separation tank.

In addition, since the recovered water that remains in the recovery tank is filtrated water, in most cases it shows a much better SSa degree value than the recovery standard value, and the low conductivity pure water treatment system after the recovery tank shows a much better SSa degree value than the recovery standard value. The load can be reduced.

In addition, since the removal of waste sludge does not entirely depend on the sedimentation action in the sedimentation separation tank, the need to ensure a long-term calm state in the sedimentation separation tank is reduced, and therefore the water to be treated is transferred to the separation tank. It is possible to receive the water for a short period of time or all the time, and as in this embodiment, it is also possible to eliminate the backwash water receiving tank in the previous stage of the separation tank.

In addition, although the said Example demonstrated the case where the backwash water receiving tank was abolished, it goes without saying that this may be installed. Further, although the description has been made regarding the removal of waste sludge from backwash water, the present invention can be sufficiently applied as a waste sludge removal device for other types of water to be treated.

As explained above, according to the present invention, waste sludge contained in treated water can be removed without being restricted by the settling time in the settling tank.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional example, Figure 2 is a diagram comparing changes in SS concentration with respect to sedimentation time for each filter.
FIG. 3 is a circuit diagram showing an example of the present invention. 1... Backwash water receiving tank, 2, 6.8... Pump, 3
...Sedimentation separation tank, 4.Supernatant water, 5.Waste sludge, 7.Package collection tank fi, 9.Circulation piping, 1o.
...Filter, 12...Circulation piping, 13...Filter. Agent Patent Attorney Akira Takahashi 751b1

Claims (1)

[Claims] 1. Put water containing waste sludge into the tank and temporarily store it.
In a nuclear power plant waste sludge removal device comprising a sedimentation separation tank that settles and separates and removes waste slough 7 and a recovery tank that recovers supernatant water of the sedimentation separation tank, supernatant water is circulated to the sedimentation separation tank. A waste sludge removal device for a nuclear power plant, characterized in that a circulation pipe is provided, a filter is connected to the pipe, and a pipe for guiding filtrated water of the filter to the recovery tank is connected to the pipe. .