Patent Number: 047864656
Section: claims

1. A method of converting a vertically downward flow of bypass coolant through a core barrel and former plates in a nuclear reactor to a vertically upward flow, comprising: a. providing coolant flow holes in the top former plate substantially in coaxial alignment with existing coolant flow holes in the intermediate and lower former plates;  b. plugging coolant flow holes in said core barrel adjacent said top former plate; and  c. plugging selected coolant flow holes in the lower former plate.  a. providing coolant flow holes in the top former plate substantially in coaxial alignment with existing coolant flow holes in the intermediate and lower former plates;  b. plugging coolant flow holes in said core barrel adjacent said top former plate; and  c. plugging alternate coolant fow holes in the lower former plate.  a. providing coolant flow holes in the top former plate substantially in coaxial alignment with existing coolant flow holes in the intermediate and lower former plates;  b. plugging coolant flow holes in said core barrel adjacent said top former plate;  c. plugging alternate coolant flow holes in the lower former plate wherein every fifth coolant flow hole plugged is partially plugged. 2. The method of claim 1, wherein the plugging pattern in said lower former plate comprises plugging alternate coolant flow holes. 3. The method of claim 2, wherein every fifth coolant flow hole plugged in said lower former plate is partially plugged. 4. The method of claim 3, wherein each of said partially plugged coolant flow holes has forty-four percent of its flow area plugged. 5. The method of claim 1, wherein said plugging of holes in said core barrel and said lower former plate is accomplished using a roll expander tool and plug. 6. A method of converting a vertically downward flow of bypass coolant through a core barrel and former plates in a nuclear reactor to a vertically upward flow, comprising: 7. The method of claim 6, wherein every fifth coolant flow hole plugged in said lower former plate is partially plugged. 8. The method of claim 7, wherein each of said partially plugged coolant flow holes has forty-four percent of its flow area plugged. 9. The method of claim 6, wherein plugging of holes in said core barrel and said lower former plate is accomplished using a roll expander tool and plug. 10. A method of converting a vertically downward flow of bypass coolant through a core barrel and former plates in a nuclear reactor to a vertically upward flow, comprising: 11. The method of claim 10, wherein each of said partially plugged coolant flow holes has forty-four percent of its flow area plugged. 12. The method of claim 10, wherein plugging of holes in said core barrel and said lower former plate is accomplished using a roll expander tool and plug.