JP3896454B2 - Underwater organism adhesion prevention method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention attaches to an underwater structure by repeatedly irradiating aquatic organisms directly with a pulsed laser of high power density radiation to kill it or stop living activities and bring it to dormancy. It is related with the method of preventing.
[0002]
[Prior art]
In power plants and factories that use a large amount of fresh water or seawater, aquatic organisms adhere to and breed on intake pipes and underwater structures, causing channel obstruction and reduced functionality. For example, in nuclear power plants and thermal power plants that use a large amount of seawater as cooling water, marine organisms adhere to pipes and underwater structures, and this gradually grows and propagates in large quantities. Operational problems such as increased shaft driving force due to blockage, reduced heat exchanger efficiency, and equipment damage have been caused.
Therefore, in these facilities, it is necessary to take a means for preventing underwater organisms from adhering to intake pipes and underwater structures.
[0003]
By the way, as a method for preventing the adhesion of underwater organisms, chemical treatment methods using active oxygen, active metal ions, antifouling agents, etc., physical treatment methods using heat, electricity, ultrasonic waves, etc., sponge balls, water jets, removal There is a known mechanical treatment method that removes aquatic organisms that have been implanted using tools, etc., but the chemical treatment method is intended to make environmental contamination due to chemicals used and chemicals generated safe. In addition, the physical processing method and the mechanical processing method use special equipment, which requires a large expense for maintenance, consumes a lot of energy, and has a recurring cost. There is a drawback of being bulky.
[0004]
In order to improve such drawbacks, a method of irradiating a floating life stage larva of an underwater organism with a wavelength-convertable dye laser (Japanese Patent Laid-Open No. 5-228454), an excimer laser on microbes and microbes that are floating in water Irradiation method (JP-A-5-228457), focusing laser in water to cause breakdown, generating plasma, radicals, UV light and shock wave, thereby killing bacteria (JP-2000-2000) 153268) and the like have been proposed, but even in these methods, for example, in the case of a continuous output type argon ion laser, it is necessary to continuously irradiate with a large average power density of 300 W / cm ² or more, It was an impediment to practical use.
[0005]
[Problems to be solved by the invention]
The present invention uses chemicals and high energy to attach larvae of aquatic organisms to solid surfaces that come into contact with water in piping and other underwater structures taken from seawater, lakes, rivers, etc. Rather, it is intended to provide a method and apparatus for prevention using simple means.
[0006]
The present inventors prevent radiation organisms from adhering to intake pipes and underwater structures by irradiating the organisms contained in water taken from seawater, lakes, rivers, etc. with radiation. As a result of various researches on the method, by irradiating a pulsed laser with a predetermined peak power, killing aquatic organisms or their larvae with a significantly lower average power density compared to the case of continuous output laser irradiation or for a certain period of time It has been found that the activity can be stopped and that underwater organisms can be prevented from adhering to the underwater structure, and the present invention has been made based on this finding.
[0007]
That is, in the present invention, when an underwater organism is directly irradiated with radiation to prevent the underwater organism from adhering to the intake pipe or the underwater structure, the underwater organism existing in the water in contact with the intake pipe or the underwater structure. Or, for the larvae, a pulse laser with a pulse peak power density of 100 kW / cm ² or more is repeated under a pulse condition of an average power density of 0.01 to 1 W / cm ² when converted to a pulse width of 20 nanoseconds or less and 10 Hz. irradiated, its either continue until these are to kill, or while they are in contact with at least intake pipe or underwater structures, provide a water biofouling wherein to continue until the dormant state To do.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, the aquatic organisms existing in the water that contacts the intake pipe or the underwater structure are killed or temporarily brought to a dormant state, and the aquatic organisms adhere to the intake pipe or the underwater structure. However, the water in which the aquatic organisms exist may be either seawater or fresh water.
[0009]
Examples of organisms or their larvae include marine or freshwater organisms such as barnacles, mussels and snails and their larvae. Among these organisms and larvae, those having a photosensitive tissue, such as barnacle larvae, are repeatedly irradiated with a pulsed laser with an intensity at which the survival activity temporarily stops without being killed, so that at least intake pipes and underwater While in contact with the structure, it is preferable to take a method of bringing it into a dormant state to prevent adhesion.
[0010]
Lasers used in the method of the present invention include those having a pulse width of 20 nanoseconds or less based on, for example, excimer laser, Q-switched YAG laser, glass laser, alexandrite laser, Q-switched YLF laser, titanium sapphire laser, and the like Can be mentioned. As this pulse laser, one in the ultraviolet, visible, or near infrared region is preferably used.
These pulse lasers are adjusted to a power density of 100 kW / cm ² or more at the pulse peak by an optical system such as a lens and a mirror, and irradiated to the object to be processed as a high peak power pulse laser.
[0011]
Next, the method of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing an example of an apparatus suitable for carrying out the method of the present invention. In this example, a container containing aquatic organism-containing water is used as an irradiation object. In this figure, the laser beam 2 output from the pulse laser oscillator 1 is converted into a half wavelength by the wavelength converting means 3, reflected by the mirror pair of the mirror 4 and the mirror 5, and by the lens pair of the concave lens 6 and the concave lens 7. Then, it is shaped so as to have a power density of 100 kW / cm ² or more at the pulse peak, and is shaped and irradiated to the container 8 containing the underwater organism-containing water.
As described above, the apparatus used in the method of the present invention includes a pulse laser oscillator of 20 nanoseconds or less capable of outputting in the ultraviolet, visible, or near infrared region, a wavelength processing mirror pair corresponding to the laser wavelength, and a beam shaping lens. Alternatively, the mirror groups are arranged in series.
[0012]
If a laser having a power density at the pulse peak of less than 100 kW / cm ² is used, the effect of preventing the attachment of underwater organisms becomes insufficient, and if the pulse width exceeds 20 nanoseconds, the energy for irradiation The amount of consumption becomes large and the purpose of the reduction cannot be achieved.
[0013]
Next, FIG. 2 is an explanatory view showing an example in the case of processing the aquatic organism-containing water passing through the water pipe by the method of the present invention. In this figure, the laser beam 2 output from the laser oscillator 1 is in the horizontal direction. After being converged in the lateral direction by the control convex lens 9, it is corrected to the original parallel state by the lateral control concave lens 10, and then stretched in the longitudinal direction by the longitudinal control concave lens 11, and then flowing through the laser introduction window 12. The tube 13 is irradiated as a thin disk beam.
Then, the laser beam controlled in this way is irradiated to aquatic organisms in the running water, particularly those having a photosensitive function, and its survival activity is stopped for a certain period of time, and it is brought into a dormant state while passing through the running water pipe. Thus, these underwater organisms can be prevented from adhering to the water pipe.
[0014]
The average power density definitive to the present invention method, when converted into repeated 10 Hz, in the range of 0.01 to 1 / cm ^2. When the pulse energy of the irradiating laser is constant, by reducing the pulse width, the pulse peak power density can be increased even with the same average power density, increasing the effect of preventing the attachment of underwater organism larvae. Can be made. In other words, the effect of preventing attachment of larvae can be increased with a small laser energy by shortening the pulse. The relationship between the pulse width at the repetition rate of 10 Hz and the average power density necessary for adhesion prevention is shown as a graph in FIG. Pulse width 10 ⁰ is a case of continuous oscillation in this graph.
[0015]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
[0016]
Example 1
Larva was released by placing adult adult barnacles (Balanus amphrite) in a refrigerator, applying a thermal shock for 10 minutes, and returning to sterile filtered seawater. Larvae were immediately transferred to a beaker containing sterile filtered seawater to give diatoms (Chaetoceros gracilis, density: 3 × 10 ⁵ / ml). Larvae were transferred daily to fresh sterile filtered seawater and continued to receive diatoms until they grew to the cypris stage (day 7, adherence phase).
Approximately 15 Cypris larvae were then placed in 1 ml of sterile filtered seawater in a 2 ml volume glass container and confirmed by microscopy that all larvae were healthy and active before laser irradiation.
[0017]
Next, using the apparatus having the configuration shown in FIG. 1, the larvae were subjected to 0.1 J / s under the conditions of a second harmonic of a Nd: YAG laser (wavelength of 532 nm), a pulse width of 5 nanoseconds, and a repetition rate of 10 Hz. A high peak power pulsed laser with a cm ² pulse was irradiated for 2 seconds, 10 seconds or 30 seconds.
The laser-irradiated larvae were transferred into 25 ml of sterile filtered seawater, and the mortality and adhesion rate of Cypris larvae were examined. These experiments were repeated three times to obtain an average value. The power density at the pulse peak at this time was 10 ⁷ W / cm ² , and the average power density was 1 W per 1 cm ² .
[0018]
An example of the mortality rate of the larvae thus obtained is shown in FIG. 4 as a bar graph. When Cypris larvae were irradiated with a laser of 0.1 J / cm ² · pulse for 2 seconds, 10 seconds, and 30 seconds, the mortality immediately after irradiation was 17%, 22%, and 13%, respectively. The mortality after 3 days of irradiation was 76%, 78% and 75%, respectively. The mortality rates of the unirradiated standard samples were 0% and 19%, respectively. From this, it was found that the difference with and without laser irradiation was significant.
[0019]
The adhesion rate of the obtained larvae is shown as a bar graph in FIG.
The laser-irradiated Cypris larvae did not adhere for more than 3 days after irradiation. The adhesion rate of the unirradiated standard sample was 11% and 51% after 1 day and 3 days, respectively. The effect of preventing larvae adhesion was observed at a low power density of 1 W per square centimeter by irradiation with a pulse laser having a high peak power and a low average energy.
That is, by using a short pulse of 20 nanoseconds or less, the laser energy absorbed by the living larvae is not taken away by water, but a part of the larval tissue is destroyed, and adhesion after irradiation can be prevented. .
[0020]
Example 2
The adhesion function of marine organism larvae was suppressed using the apparatus shown in FIG. The laser used was a femtosecond laser (wavelength: 800 nm) with a pulse width of 130 femtoseconds (fs) and a repetition rate of 1 kHz. The average power was adjusted with a concave lens.
[0021]
The method for preparing barnacle larvae is the same as in Example 1. The pulse width is 130 femtoseconds (fs), and the power density at the pulse peak is 10 ⁹ W / cm ² . The average power density is 1 W per cm ² . When this is converted to 10 Hz repeatedly under the same conditions as in Example 1, the average power density corresponds to 0.01 W.
FIG. 6 shows an example of the ratio of larvae that have stopped moving (immobilized larvae) thus obtained. When Nauplius IV larvae were irradiated with a 0.305 mJ / cm ² laser for 5 seconds, 15 seconds, 30 seconds, and 60 seconds, the percentage of immobile larvae after 15 minutes of irradiation was 15% and 17%, respectively. 43% and 47%. The ratio of immobile larvae among the unirradiated larvae was 7%. The difference due to the presence or absence of laser irradiation was significant, and the effect of preventing the attachment of larvae was observed by pulse laser irradiation with high peak power and low average energy. At a laser energy density of 0.305 mJ / cm ² , larval mortality was zero.
[0023]
In this way, by reducing the pulse width to about 130 femtoseconds (fs), it is possible to cause recoverable damage to the tissue having photosensitivity of living organisms, and to stop the activity for a certain time after irradiation. By designing the flow path based on this activity stoppage time, it is possible to prevent the attachment of living organisms without environmental burden.
[0024]
【The invention's effect】
According to the present invention, underwater organisms adhere to underwater structures that come into contact with seawater or fresh water, without using harmful chemicals, without large energy consumption, and without changing the layout of conventional devices. By simply changing the continuous laser output to pulse output, it can be efficiently prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an apparatus used for carrying out the method of the present invention.
FIG. 2 is a schematic diagram of an apparatus for applying the present invention to a water pipe. FIG. 3 is a graph showing a relationship between an average laser power density and a pulse width necessary for preventing adhesion.
FIG. 4 is a bar graph showing the mortality rate of barnacle larvae due to YAG laser irradiation.
FIG. 5 is a bar graph showing the adhesion rate of barnacle larvae by YAG laser irradiation.
[6] bar graph showing the percentage of femtosecond barnacle immobile larvae that by the laser irradiation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Laser beam 3 Wavelength conversion means 4,5 Mirror 6,7 Concave lens 8 Container 9 Lateral control convex lens 10 Lateral control concave lens 11 Vertical control concave lens 12 Laser introduction window 13 Flow pipe

Claims (3)

In preventing underwater organisms from adhering to an intake pipe or an underwater structure by directly irradiating the underwater organisms with respect to the underwater organism or its larvae existing in water in contact with the intake pipe or the underwater structure, the power density 100 kW / cm ² or more pulsed lasers at a pulse peak, a pulse width of 20 nanoseconds or less, repeatedly irradiated with an average pulse conditions of the power density of 0.01 to 1 / cm ² when converted to 10 Hz, its these A method for preventing the adhesion of underwater organisms, characterized in that the method continues until the water is killed. Hit the water intake pipe or underwater structure with radiation irradiated directly into the water organisms aquatic organisms prevented from adhering to marine organisms or their larvae present in the water in contact with said mounting water pipe or underwater structures, the power density 100 kW / cm ² or more pulsed lasers at a pulse peak, a pulse width of 20 nanoseconds or less, repeatedly irradiated with an average pulse conditions of the power density of 0.01 to 1 / cm ² when converted to 10 Hz, which is at least A method for preventing attachment of underwater organisms, which is continued until a dormant state is reached while contacting an intake pipe or an underwater structure.   The method for preventing attachment of underwater organisms according to claim 1 or 2, wherein the pulse laser is in the ultraviolet, visible or near infrared region.

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