MXPA93003348A - Nuclear deriver piston immobilizer system and valv assembly impeller system - Google Patents

Abstract

The present invention relates to an immobilization piston drive system for the selective shutdown of a nuclear reactor vessel having a core area, comprising: (1) a reactor housing, (2) a plurality of guide tubes placed inside the reactor housing: (3) a control rod housed concentrically within each of the guide tubes and having first and second ends, the first end being in communication with the core area; a plurality of impeller piston housings extending through the reactor housing; (5) an impeller piston assembly positioned within each of the impeller piston housings, each of the impeller piston assemblies is operably secured with a rod of control at the second end of the control rod and at one end of the drive piston assembly, and has a piston head at the other end thereof; (6) a hydraulic control line extending to the head of the piston and to the reactor housing for the transmission of the hydraulic control fluid in order to manipulate the drive piston; (7) an accumulator means including a pressure element in the hydraulic control line for selective pressurization of the hydraulic control fluid; (8) a means for introducing the hydraulic control fluid into the control line; (9) a check valve means downstream of the medium for introducing the hydraulic control fluid; hydraulic control fluid and includes a housing in the hydraulic control line, for selective blocking of fluid communication between the hydraulic control line and the means for introducing the hydraulic control fluid into the control line means, while the fluid Control is selectively pressurized by the accumulator to move each piston head and control rod towards the core; (10) a fluid flow path through the check valve housing; (11) a plurality of fluid passages communicating selectively with each other through the fluid flow path; (12) a valve seat defined in the check valve housing; (13) a valve head positioned within the check valve housing and movable between a first position den where the check valve housing is sealably secured relative to the valve seat retention, and a second position wherein the check valve head is positioned remote from the check valve seat and a plurality of the fluid passages remain in fluid communication through the fluid flow path to allow for the transmission of fluid. hydraulic control fluid to the hydraulic control line in order to charge the accumulator, and (14) a resistance medium defined to the outside in the valve head to resist movement of the check valve head between the first and second positions, the ball check valve head further defines at least one passage of fluid flow through the resistance medium for fluid communication Continues with each of the fluid passages when the check valve head is in the second position

Description

"NUCLEAR REACTOR IMMOBILIZER PISTON DRIVE SYSTEM AND VALVE ASSEMBLY" INVENTOR: JOSEPH S. MILLER JOHN J. LYNCH.

NATIONALITY: NORTH AMERICAN CITIZEN RESIDENCE: 6780 MARTIN STREET, ZACHARY LOUISIANA 70791. E.U.A. 2225 COLLEGE DRIVE, APT.45, BATON ROUGE, LOUISIANA 70808 E.U.A OWNER: GULF STATES UTILITIES COMPANY NATIONALITY: NORTH AMERICAN SOCIETY.

RESIDENCE: 350 PINE STREET, BEAUMONT TEXAS 77701 E.U.A.

SUMMARY OF THE INVENTION An immobilization piston impeller system and valve assembly for the shutdown of a nuclear reactor is provided. "Vibration" in a check valve assembly that occurs during the loading and / or re-loading of the control fluid within a control line is eliminated by providing a valve head and a head endurance portion. of valve to resist the movement of the valve head when pushed from the coupling to its seat during the charging or recharging procedure.

BACKGROUND OF THE INVENTION (i) FIELD OF THE INVENTION: The invention relates to nuclear reactors, and, particularly, to a system for shutting down the reactor, including a valve assembly to eliminate "vibration" during operation. (2) BRIEF DESCRIPTION OF THE PREVIOUS TECHNIQUE: A nuclear reactor converts nuclear energy, that is, atomic energy, into atomic energy. The nuclei of the atoms with are, broadly speaking, of elementary particles called protons and neutrons. Protons have a positive electric charge, while neutrons have no charge and are electrically neutral. The very powerful pink action forces act between these particles, which are referred to together as "nucleons", and hold them together in the nucleus. Heavy atomic nuclei, however, are not so. Like the light ones, because in the former the repulsive forces exerted by the pistons loosen the structure of the nucleus. Due to this reason, it is possible to cause the physio of the heavy nuclei, such as those of uranium 235, by bombarding them with free neutrons. As a result of this collision, the nuclei of uranium 235 begin to vibrate, and these vibrations become so violent that the nucleus divides into several parts, that is, into a barium nucleus and a nucleus of criptdn. The "fission products" go at considerable speed, collide with matter in a certain place in the reactor and release the kinetic energy as heat. This is a conversation about nuclear energy in heat. In addition, the fission products and the heat formed in the uranium fission, however, also release the new neutrons which in turn can cause the fission of more uranium atoms. In this way a chain reaction begins. The neutron strikes the uranium-235 nucleus and briefly forms the intermediate product, uranium-236, which decays spontaneously into strontium and xenon. Additional neutrons are released in this fission process that sustain the chain reaction. In order to be able to use these neutrons, which are emitted from the original parent nucleus at high speed, for additional fissionable processes, they have to decelerate. Low-speed neutrons are best suited for dividing high-speed neutron atoms. The slower neutrals can interact with the uranium nucleus for a longer period of time, while the faster neutrons remain in the vicinity of the nucleus for too short a period of time to initiate the fission process. The speed of the neutrons moderates causing the same ones to collide with the light atoms, the large numbers of which must be incorporated in a reactor for this object. The materials consist of these lighter items, for example, are graphite and water. The neutrons that have slowed down in this way, will then cause the fission of the additional uranium-235 nuclei. Each fission process gives rise to new neutrons, so that the chain reaction is self-healing and the reactor consequently remains in operation. In the case of a moderate reactor with water, the uranium is installed in the form of metal rods in a container filled with water. The fission is carried out within the uranium and the neutrons that are released in the process and march towards the surrounding water, where they collide with the hydrogen and light oxygen atoms and moderate, that is, they lose speed. These decelerated neutrons re - enter the de uranium rods with a certain probability and in them cause other fission reactions to take place. The fission products formed as a result of these reactions, give off their energy to the uranium, which, in turn, transmits the same water. This hot water is used to spin a turbine that generates electricity. To ensure that the reactor does not stop working or overheats excessively, the rate of neutron formation within it has to be controlled with considerable accuracy. This is effected by means of the control rods, which consist of a neutron absorbing material and which are inserted into the reactor core to an exactly variable depth. This depth of penetration must be just enough to ensure that on average per fission only one neutron remains available to produce another fission reaction. Since the fission products are highly radioactive, the reactor must be enclosed in a thick box of concrete called the "protector".

A type of reactor moderated with water is sometimes referred to as a boiling water reactor. In these reactors, an emergency system is provided to paralyze the reaction in case of an indication that the reaction control may be lost or made difficult. Typically, these systems incorporate a hydraulic control line that has a control fluid therein, such as a charge water, or similar, which is pressurized by means of an accumulator tank having a piston that has a side exposed to a gaseous substance, such as nitrogen. This control line extends to a main drive piston face. A duct or charging water head supplies the control fluid to the control line and the accumulator. A check valve assembly is placed between the charging water head and the accumulator assembly in order to selectively allow charging and re-charging of the control line and the accumulator. If it is necessary to paralyze the container of the nuclear reactor, a solenoid-operated valve is opened in the control line between the accumulator and the main-drive piston in order to allow the fluid to be pressurized within the order of 1 26.54. kilograms per square inch manometrical, drives the main piston inwards inside the reactor vessel. As the main drive piston moves, the pressure in the control line decreases to approximately 77.33 kilograms per square centimeter gauge and the check valve assembly downstream of the load water head immediately opens to recharge the line. control and the accumulator. IF flow of the fluid in the control line during the stoppage is extremely fast and the recharge of the accumulator starts spontaneously. It has been found that this recharging results in the ball or sphere member of the check valve assembly downstream of the charging water head upstream of the accumulator bouncing up and down violently, or "vibrating", causing , in turn, that large massive hydrodynamic loads are made in the pipe system for the paralyzing assembly. The present invention is directed to solve this problem.

SUMMARY OF THE INVENTION In the present invention, the valve head element in the check valve assembly described above is designed to provide a drag in the charging water, or control fluid, in order to prevent vibration. When operating to provide Buido communication between the charge water head and the accumulator, the valve head element incorporated in the present invention allows the fluid pressure equalization around the valve head element, as the valve head element is lifted from its seat, and the lift of the valve head element is continuously supported. As the drag is increased around this valve head element when it rises from its seat, the velocity of the fluid flow around it increases so that the position of the valve head element in the position is used. "auerta". Furthermore, the element forming the valve head in the check valve assembly is also designed in such a way that the sealing coupling between the valve head and the valve seat is not adversely affected during the sealing coupling.

Accordingly, an immobilization depiston drive system is provided for the selective shutdown of the nuclear reactor container. The immobilization piston drive system includes a reactor housing and a plurality of guide tubes that are placed inside the housing. A control rod is concentrically housed within each of the guide tubes and has first and second ends with the first of the ends being in communication with the core area in the reactor housing. A plurality of drive piston housings extend through the reactor housing, with a driven piston assembly positioned inside each of the drive piston housings Each of the drive piston assemblies is reliably secured with a control rod at the second end of the control rod and at one end of the drive piston assembly. A piston head is placed on the other end of the piston assembly. In a preferred form, means are provided to selectively immobilize each of the drive pistons against movement in the drive piston housing in one direction, having both mechanical and hydraulic drive elements therein. An accumulator includes a pressurizing element, such as a nitrogen tank, is provided in the control line for selective pressurization of the hydraulic control fluid. The medbs for introducing the control fluid into the control line are provided through the water head. The check valve means includes a housing carried in the hydraulic control line for selective blocking of fluid communication between the control line and the means for introducing the hydraulic control fluid into the control line, while the fluid of Control is selectively pressurized by the accumulator to move each of the control rods towards the core. A fluid flow path is defined through the housing of the check valve, and a plurality of the flow passages communicates selectively with another through the control flow path. A valve seat is defined in the housing of the check valve and a valve head is placed within the check valve housing and is movable between a first position, wherein the check valve housing is sealable in relation to the valve. seat of check valve and a second position where the valve head se.coloca - <; | 0 - remote to the check valve seat, and a plurality of fluid passages remain in fluid communication through the fluid flow path to allow transmission of the control fluid to the control line, in order to charge the accumulator. Resistance means are defined on the valve head to resist movement of the check valve head between the first and second positions, with the valve head further defining at least one passage of fluid flow through the medium of resistance, for communication of continuous flow with each one of the fluid passages, when the head of the check valve is in the second position.

BRIEF DESCRIPTION DB THE DRAWINGS Figure 1 is a schematic illustration of the immobilizer piston drive system of the present invention. Figure 2 is a schematic illustration of the immobilization piston drive assembly of the present invention illustrating the multiple use for a number of driving pistons. Figure 3A is a cross-sectional view looking downward of a housing for the check valve assembly of the present invention. Figure 3B is a view similar to that of Figure 3A, illustrating a valve head element positioned inside the housing. Figure 3C is a cross-sectional view of the valve assembly shown in Figures 3A and 3B. Figure 4A is an outside view in the embodiment of a spherical valve head of the present invention. Figure 4B is a spherical valve head assembly of Figure 4A, positioned within its housing. Figure 4C is a view of the spherical valve head shown in Figure 4A taken from a bottom point facing upward to the plate portion of the valve head. Figures 5A and 5B are perspective views of an alternative configuration of a spherical valve head of the present invention. Figure 6 is a perspective view of yet another alternative embodiment of a pair spherical valve head incorporated in the present invention. Figure 7 is an illustration of a typical prior art valve assembly as would be used in the plunger impeller drive system of the nuclear reactor of Figure 1. Figure 8 is a cross-sectional view, looking downwards. of a preferred alternative embodiment of the valve assembly embodied in the present invention.

Figure 9 is a cross-sectional view taken along lines 9-9 of Figure 8. Figure 10 is a cross-sectional view taken along lines 10-10 of Figure 8.

DESCRIPTION OF THE PREFERRED MODALITY Now, first referring to Figure 1, there is shown an immobilization piston driving system 100 for use in a nuclear reactor 10 which includes a housing 11 of the reactor vessel having an interior 12. The core flush 13 includes a rod 15 placed inside the interior 12 and inside a guide tube 14 therein. Of course, it will be appreciated that the nuclear reactor 10 of the present invention will have a number of 100 i piston immobilization systems thereon, one for each control rod, as schematically illustrated in Figure 2. SI area 13 The core is seated on a core plate 13A which is connected to a series of cylindrical guide tubes 14 extending inwardly, each guide tube 14 receiving therein an inwardly extending control tube 15 having a first end 17 oriented inwardly within the core area 13. A second end 17 of each control rod 15 is secured as a coupling 18 with a driving piston assembly 20 within a housing 19 of the driving piston that extends through the housing 11 of the reactor vessel and into the interior 12 thereof. . The drive piston assembly 20 consists of a plurality of limbs 21, 22, 23 and 24 similar to a piston, each piston member having a circumferentially oriented upwardly facing face 21B, 22B, 23B and 24B facing surface, respectively, for contact with a beveled surface 28 shaped to form companion in a collar head 27 projecting laterally into the housing 19 of the drive piston. As the im pulser piston assembly moves up through the housing 19 and into the interior 12 of the housing 11 of the reactor vessel, the respective beveled surface 2 * | B, 22B, 23B or 24B will come into contact and the bevel 28 will be coupled to overcome the lateral thrust defined by a spring 30 which extends to a ring 29 at the outward end of the head 27 of the collar. Also, each of the piston members 21, 22 and 23 of the drive piston assembly 20 has a latching surface 21A, 22A and 23A extending circumferentially downwardly, which are selectively secured against the top shoulder of the head 27 of the collar for holding the drive system assembly against movement in a downward direction and outside the interior 12 of the housing 11 of the reactor vessel. The lower piston member 24 does not have this latch surface facing down, but has an enlarged piston head 25 at its lower end. The selective immobilization means 26 of the driving piston assembly 20 includes the spring 30, the collar head 27 and the respective mating surfaces or surfaces of each of the piston members 21, 22, 23 and 24, that is to say the beveled surfaces. such as 21b, and latch surfaces, such as 21A. The piston-drive assembly 20 is pushed upwards to move the respective control rod 15 through the guide tube 14, by means of the hydraulic pressure applied to the piston head 25 to move the drive piston assembly 20 upwards. This hydraulic pressure is applied by means of application of charge water, the control fluid, which is carried inside a duct 51 of the head and which enters by means of a line 5 A of the head towards a check valve 50 (Figure 1). and Figure 3C). The check valve 50 extends to a control line 46 through an opening 46A to a control fluid accumulator 47. The accumulator 47 contains a sealing plate 47a which separates the control fluid from a pressurizing fluid such as nitrogen, introduced through the line 48 of the accumulator 47 for pressurization therein of the control fluid. Line 48 extends to a tank 49 containing an adequate amount of pressurizing fluid, such as nitrogen. The control line 46 extends by a "T" 45 the teral to a line member 44 which extends to an inlet valve 43, which can be activated by solenoid, and which in turn extends to a portion 38. of line r received through an opening 36 in a housing 37 of a means 35 of check valve. The control valve means 35 contains a spherical valve head element 62 which normally seals an opening 34 therein and which also receives a line 32 extending towards an opening 33 in the interior 12 of the housing 11. of the reactor vessel. A third opening 40 is positioned within the housing 36 of the check valve means 35 to receive a line 41 extending to the lower end of the housing 1 of the driving piston, and below the head 25 of the piston. A line member 39 extends from line 38 above the check valve means 35 to allow the control rod 15 to be removed. In this way, the hydraulic control line means 31 includes the control line 46 and the members 44, 38 and 41. Figures 3A, 3B, 3C, 4A, 4B and 4C illustrate a preferred retention valve 50. The check valve 5 has a housing 50a having a hollow interior and surface 36A, 36B, 36C and 36D internal semicircular contoured. Each contoured inner surface 36A, 36B, 36C and 36D has companion 36K backs, of slightly arched internal diameter that separate each internal surface (Figure 3A). As shown in Figures 3B and 4A, a spherical valve head 52 is secured therein at a central point 52A positioned 180 ° at the contact point 52B of the ceiling between the valve head 52 and its valve seat 53. (Figure 4B). A flat plate member 57 is secured to the spherical element 52 by any known means such as spot welding, extrusion or the use of a resin fastener. As shown in Figures 3B, 3C, 4A and 4B, the resistance means 56 consists of the flat plate 57 in the spherical element or ball 52. The flat plate 57 has a portion 58 of external diameter extending towards, but that does not come into contact with the arcuate surface 36K of respective internal diameter in the housing 50A, the area between the outer diameter 58 of the flat plate 57 and the arcuate surfaces 36K that provide a fluid flow area. Also, a series of semicircular extensions 58A are provided around the flat plate 57 and are received through the respective contoured internal surfaces 36A, 36B, 36C and 36D. Again, the outer smooth surface or edge of the respective semicircular elements 58A do not contact the surfaces 36A, 36B, 36C or 36D internal companions thereby providing the same additional fluid flow areas. As shown in Figure 4B, the valve head 52 is shown in a first position 54 sealingly engaged in a valve seat 53. The. Valve head 52 is shown uncoupled from seal coupling in valve seat 53 and placed in unsealed position as shown in Figure 3C. During the operation of re-charging the accumulator 47 as will be discussed below. 0 When in the position shown as in Figure 3C, the valve assembly provides a flow path 42 (Figure 7) through the housing of the valve 50 of FIG. The control fluid entering the control valve 50 via the line 51 a from the charging water head 51 can be transmitted via the control line 46 to the accumulator 47. As shown in FIG. shown in Figure 2, a plurality of accumulators 47 through respective lines communicate with the check valve assemblies 0 and are activated by means of the loading pump 63. As shown in Figures 5A and 5B, an alternative form of the spherical valve element 52 would include a series of semicircular elements 63 placed a. along a line in the approximate center of "a sphere 52. As shown, the semicircular elements 63 are placed around the spherical element 52 in such a way that four of these elements are provided of course. in Figure 6, a pair of these semicircular elements 63 can provide and be placed at? 8? a of each other around the outside on the central line of the sphere 52. The resistance means 56 of the present invention can be designed to accommodate any The flow rate and fluid type desired and the geometry of this resistance means will of course depend on the type of valve head element that is selected, ie ball, conical, plug or similar element, as well as the configuration of the housing for the valve head element.Therefore the following calculation can be used to provide a means of satisfactory resistance and a seating element and valve head to be incorporated in the present invention: a valve head in the form of a plug is proposed for which the space between the valve head and the valve housing is defined by (12 micrometers Q height) 1/3 y / \ t perimeter g = distance from space μ = fluid viscosity height = height of -the straight sides of the plug (excluding the top element) Q = flow / \ t = pressure drop; must be greater than the weight of the movable valve head divided by the projected area perimeter = internal perimeter of the valve housing This equation is applicable to a fluid with a Reynold number that is defined for the flow beyond the movable valve head within the laminar scale: Pvg. = (P o) < 2000 μ and. perimeter V = fluid velocity. Referring now to Figures 8, 9 and i, the valve assembly incorporated in the present invention is shown with the valve head in the form of a plug, similar numbers for like pieces being used as in Figures 3a, 3b, 3c, 4a and 4b. As shown in Figure 9, the valve head 52 is in the form of a plug having an expanded diameter upper portion 57, the entire configuration of which is shown in Figure 8. 31 plug 52 has an elongated outer diameter 70 which extends to a lower inwardly bevelled shoulder 71 which contacts a shoulder member 76 extending inwardly in the housing 50a, so as to provide a seal coupling point 53 between the screw 52 and your 50th companion accommodation. Also, the housing 50 has a wall 73 of elongated internal diameter extending to a lower inclined shoulder 74 which extends inward, abbreviated and ending in a vertical plane 75 which, in turn, extends to a horizontal shroud 76 having a point 53 for sealing engagement with the plug 52, when the plug 52 is in the position as shown in Figure 9. 31 shoulder 76 extends to and ends in a wall 77 of vertical internal diameter which defines the passage of fluid flow beneath a terminating end 72 of the plug 52. It will be appreciated that the pressure inside the interior 12 of the reactor vessel can be transmitted through the opening 33 to the line 32, through the medium 35. of the check valve and to the line 41 to apply pressure through the underside of the piston head 25, in case the pressure within the hydraulic control line 8 decreases to less than one normal amount, thereby providing a backup activation for the immobilization piston drive system 100.

FUNCTIONING Before the activation of the immobilization piston impeller system 100, the piston assembly 20 and the respective control rods 15 will be placed inside the reactor 1 or nuclear as shown in Figure 1. In case of an immediate shutdown of the reactor 10 nuclear, is transmitted to the central valve 43 and the valve 43 opens to communicate with the lines 44 and 38. When this occurs, the spherical valve head element 62 moves to its seat to block the opening 34 to control the fluid that will enter the lines 38 and 41 of the head 25 of the piston. As the fluid passes from the accumulator 47 to the control lines 46, 44, 38 and 41 to the piston head 25, the increased pressure below them within the housing 1 9 will propel the piston head 25 toward up to move the piston members 21, 22, 23 and 24 upward in the guide 14, in order to move the control rods 5 to a safety position within the reactor 10. As the piston head 25 moving upwards, the pressure inside the accumulator 47 as well as in the control lines 46, 44, 38 and 41 will disinuitarily range from approximately 126.54 kilograms per square centimeter hand-metric to approximately 77.33 kilograms per square centimeter electric hand. Therefore, the pressure inside the charging head 51 which now exceeds that within the control lines and the accumulator 47, will push the seal coupling valve head 52 into the valve seat 53, to move it from the position as shown in Figure 4B to the position as shown in Figure 3C. Now, a flow path 42 will be established within the check valve 50 in order to allow the recharge of the accumulator through the transfer of the charging water or the control fluid through the control line 46 towards the accumulator 47. The fluid will pass around the exterior of the valve head 52 and within the fluid flow areas 36E, 36F, 36G, 36H, 361 and 36J. However, because the spherical member 52 includes the plate member 57, the dynamics of the fluid will be altered and there will be resistance for fluid flow through the element 52 from under the element 52 to the top of the plate 57, thus "cushioning" the movement of the valve 52. In opposition to rapid upward and downward movement in the housing, the spherical member 52 and the plate 57 will be effectively suspended at the central position in the housing, thus avoiding the effect of "vibration" on the former arc components. Once the accumulator 47 has been adequately repressed, the valve head 52 will fall and again be sealably engaged in the valve seat 53. Even though the invention has been described in terms of the specified modalities that are set forth in detail, it should be understood that this is by way of illustration only and that the invention is not necessarily limited thereto since alternative modalities and techniques will become apparent. operation for those skilled in the art in view of the exhibition. Therefore, modifications are proposed that can be made without deviating from the

Claims (11)

spirit of the invention described. Having described the invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: /

1 . An immobilization piston drive system * for the selective shutdown of a nuclear reactor vessel having a core area, comprising: (1) a reactor housing; (2) a plurality of guide tubes positioned within the reactor housing; (3) a control rod housed concentrically within each of the guide tubes and having first and second ends, the first of the ends being in communication with the core area; (4) a plurality of impeller piston housings extending through the reactor housing; (5) An impeller piston assembly positioned within each of the drive piston housings, each of the impeller piston assemblies is operably secured with a control rod at the second end of the control rod and at either end of the drive piston. drive piston assembly, and has a piston head at the other end thereof; (6) a hydraulic control line extending to the head of the piston and to the reactor housing for the transmission of the hydraulic control fluid in order to manipulate the drive piston; (7) an accumulator means that includes a pressurization element in the hydraulic control line for the selective pressurization of the hydraulic control fluid; (8) a means for introducing the hydraulic control fluid into the control line; (9) a retention valve means downstream of the medium for the introduction of the hydraulic control fluid and includes a housing in the hydraulic control line, for selective blocking of the. fluid communication between the hydraulic control line and the means for introducing the hydraulic control fluid into the control line means, while the control fluid is selectively pressurized by the accumulator to move each piston head and control rod towards the nucleus; (10) a fluid flow path through the housing of the check valve; (11) a plurality of fluid passages that selectively communicate with one another through the fluid flow path; (12) a defined valve seat - in the housing of the check valve; (13) a valve head positioned within the check valve housing and movable between a first position wherein the housing of the check valve is sealably secured relative to the check valve seat, and a second position where the The check valve head is positioned away from the check valve seat and a plurality of the futu- re passages remain in fluid communication through the fluid flow path to allow the transmission of hydraulic control fluid to the line of flow. hydraulic control in order to charge the accumulator; and (4) a resistance means defined to the outside in the valve head to resist movement of the check valve head between the first and second positions, the spherical check valve head further defines at least one passage. of fluid flow through the resistance means for continuous fluid communication with each of the fluid passages when the check valve head is in the second position.

2. The immobilization piston drive system according to claim 1, further comprising: means for selectively locking each of the drive pistons against movement in the drive piston housing in one direction.

3. The immobilization piston drive system according to claim 1, wherein the ball valve head is a ball element and the resistance means includes a flat plate carried by the ball element and having a central point. placed at 18 degrees from a center line at the sealing contact point between the valve head and the valve seatthe flat plate having a plurality of external diameters, and each outer diameter being smaller than the internal diameter of the housing.

4. The immobilization piston drive system according to claim 1, wherein the spherical valve head is a circular ball element.

5. The immobilization piston drive system according to claim 1, wherein the spherical valve head is a circular ball-and-the-resistance means includes a plurality of protrusions carried by and extending outward from the ball element.

6. The immobilization piston drive system according to claim 4: the plurality of protuberances is carried by the ball element along a line through the ball element having a plane positioned horizontally towards a line defined at the intersection of the valve head and the valve seat at the point of sealing between them.

7. Sn a check valve assembly including a housing, a fluid flow path through the housing, a plurality of fluid passages that selectively communicate with each other through the fluid flow path, and a valve seat defined in the housing, the improvement comprising: a spherical valve head positioned within the housing and movable between a first position, wherein the valve head is sealably secured relative to the valve seat, and a second position. wherein the valve head is positioned remote from the valve seat and a plurality of the fluid passages are in fluid communication through the fluid flow path, the ball valve head includes a resistance means which is Defined outside to resist valve head movement between the first and second positions, the spherical valve head further defines by a a trajectory of fluid flow adjacent to the resistance medium and in common selection of selective fluid with each of the fluid passages

8. The improvement according to claim 7 - the housing has a first continuous internal diameter, and wherein the spherical valve head is a circular ball element, and the resistance means includes a flat plate carried safely by the ball element and having a central point positioned at 18 degrees from a central line at the sealing contact point between the valve head and the valve seat, the flat plate has a plurality of external diameters, each outer diameter being smaller than the outer diameter. inner diameter of the housing. The improvement according to claim 7, wherein the spherical valve head is a ball element and the resistance means includes a plurality of protrusions carried by and extending outwardly from the ball element. 10. The improvement in accordance with claim 9: the plurality of protuberances being carried by the ball element along the line through the ball element which has a horizontally placed plane to a line defined at the intersection of the valve head and the valve seat at the point of sealing between them. The improvement in accordance with claim 7, wherein the spherical valve head is a ball element and the resistance means includes a series of defined protrusions carried by and extending outwardly of the ball element. IN WITNESS WHEREOF, I have signed the above description and the claims of Novelty of the invention, as appendant of GULF STATES UTILITIES COMPANY., And / or Mexico City, Republic of Mexico on June 4, 1993.