Patent Number: 052375951
Section: claims

1. An improved guide plate of the type used in the guide tubes of a pressurized water type nuclear reactor and having a central orifice for conducting coolant, and guide holes interconnected by slots for guidingly conducting the movement of control rodlets and control rod vanes through its respective guide tube, wherein the improvement comprises at least one vent opening in said guide plate for reducing both fretting and frictional contact between the control rodlets and said guide holes by lowering the pressure differential and the amount of turbulent flow across the plate. 2. The improved guide plate defined in claim 1, wherein the improvement further comprises a plurality of said vent openings. 3. The improved guide plate defined in claim 2, wherein said plurality of vent openings are uniformly distributed around the periphery of the guide plate. 4. The improved guide plate defined in claim 3, wherein said vent openings are in the form of gaps between the outer edge of the guide plate and the inner surface of the guide tube that are at least 0.1250 inches wide. 5. The improved guide plate defined in claim 2, wherein the thickness of the guide plate is increased to compensate for any diminishment of shear strength caused by the provision of said vent openings through said plate. 6. The improved guide plate defined in elaim 2, wherein each of said vent openings includes a chamfer at both ends to reduce turbulence in the flow of coolant passing through said openings. 7. The improved guide plate defined in claim 2, wherein said vent openings are uniformly distributed between said slots interconnecting said circular guide holes. 8. The improved guide plate defined in claim 7, wherein only one vent opening is provided between every two adjacent slots. 9. The improved guide plate defined in claim 8, wherein each of said vent openings is located adjacent to the midpoint of each of the two adjacent slots it is positioned between. 10. The improved guide plate defined in claim 2, wherein the total cross sectional area of said vent openings is between about 80 and 120 per cent of the area of said central orifice. 11. An improved guide plate of the type used in the guide tubes of a pressurized water type nuclear reactor and having a central orifice for conducting coolant, and circular guide holes interconnected by slots for guidingly conducting the movement of control rodlets and control rod vanes through its respective guide tube, wherein the improvement comprises a plurality of vent openings in said guide plate for reducing both fretting and frictional contact between the control rodlets and the guide holes and for reducing the rodlet drop time through the guide tube by reducing turbulence in said coolant flow through said central orifice and by lowering the pressure differential across the plate. 12. An improved guide plate as defined in claim 11, wherein each of said vent openings includes a chamfer at both ends to reduce turbulence in the flow of coolant passing through said openings. 13. An improved guide plate as defined in claim 11, wherein said vent openings are uniformly distributed between said slots interconnecting said circular guide holes. 14. An improved guide plate as defined in claim 13, wherein only one vent opening is provided between every two adjacent slots. 15. An improved guide plate as defined in claim 14, wherein each of said vent openings is located adjacent to the midpoint of each of the two adjacent slots it is positioned between. 16. An improved guide plate as defined in claim 11, wherein the total cross sectional area of said vent openings is between about 80 and 120 per cent of the area of said central orifice. 17. An improved guide plate as defined in claim 11, wherein said vent openings are in the form of gaps between the outer edge of the guide plate and the inner surface of the guide tube that are at least 0.1250 inches wide. 18. An improved guide plate as defined in claim 11, wherein said plurality of vent openings are uniformly distributed around the periphery of the guide plate. 19. An improved guide plate as defined in claim 11, wherein said vent openings are in the form of gaps between the outer edge of the guide plate and the inner surface of the guide tube that are at least 0.1250 inches wide. 20. An improved guide plate as defined in claim 11, wherein the guide holes are chrome plated to further reduce frictional engagement between the control rodlets and the guide plate, and to render the surface of said holes corrosion proof. 21. An improved guide plate of the type used in the guide tubes of a pressurized water type nuclear reactor and having a central orifice for conducting coolant, and circular guide holes interconnected by slots for guidingly conducting the movement of control rodlets and control rod vanes through its respective guide tube, wherein the improvement comprises a plurality of chamfered vent openings uniformly disposed between said slots in said plate for reducing both fretting and frictional contact between the control rodlets and the guide holes and for reducing the rodlet drop time through the guide tube by reducing turbulence in said coolant flow through aid central orifice and by reducing the pressure differential across the plate. 22. An improved guide plate as defined in claim 21, further including vent gaps disposed between the outer edge of the guide plate and the inner surface of the guide tube. 23. An improved guide plate as defined in claim 22, wherein the combined cross-sectional area of the vent openings between said slots is between 50 and 60 per cent of the area of said central orifice, and wherein the cross-sectional area of said vent gaps is between 50 and 60 per cent of the area of said central orifice. 24. An improved guide plate as defined in claim 21, wherein the thickness of the guide plate is increased to compensate for any diminishment of shear strength caused by the provision of said vent openings through said plate. 25. An improved guide plate as defined in claim 21, wherein the guide holes are chrome plated to further reduce frictional engagement between the control rodlets and the guide plate, and to render the surface of said holes corrosion proof.