Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within...
Reexamination Certificate
1998-06-11
2001-05-29
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
C376S249000, C376S245000, C376S463000
Reexamination Certificate
active
06240153
ABSTRACT:
SPECIFICATION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cleaning studs or bolts. More particularly, the invention relates to an apparatus for safely and effectively cleaning the studs used to secure reactor heads on nuclear reactors.
2. Description of the Related Art
Nuclear reactor vessels typically have had a reactor head secured to the reactor vessel by large studs or bolts. The reactor studs were very large, typically around 6 feet in length and weighing up to one thousand pounds (1000 lbs.) or more. When the nuclear reactors were shut down at scheduled intervals for maintenance and inspection, the reactor studs had to be removed for cleaning and inspection.
The size and weight of the reactor studs made cleaning of the studs a cumbersome and time consuming process. The cleaning process traditionally involved using an A-frame assembly and a manual chain hoist to move the reactor studs into position for cleaning. The reactor studs were then cleaned by hand using brushes or rags to remove any build up of oxides, residues, or dried lubricants.
There were several problems with this process for cleaning reactor studs. The cleaning process was very laborious and consumed a significant amount of manual labor. In addition, because of the possibility that the reactor studs were somewhat radioactive, personnel could only be exposed to the studs for a short period of time. Another problem with the traditional reactor stud cleaning process was that it created a large amount of waste such as rags, scrubbing pads, and brushes that had to be treated as radioactive waste.
To overcome the problems associated with manual cleaning of the reactor studs, stud cleaning machines were developed such as those disclosed in U.S. Pat. Nos. 4,165,549 and 4,452,753. These machines had housings in which a stud was placed so that the stud's longitudinal axis extended in the horizontal direction. The studs were rotated along the longitudinal axis inside the housings and cleaning was accomplished by the rotating brushes.
There were several problems with these machines. First, the stud had to be positioned in a horizontal plane requiring extra handling of the potentially radioactive stud. Additionally, the machines used a mechanical cleaning process and did not have capability to utilize solvents and other cleaning agents. Further, the machines only had the capability of cleaning one reactor stud at a time.
U.S. Pat. No., 4,630,410 similarly disclosed an apparatus having horizontal housing for cleaning reactor studs. However, in this apparatus, the rotary brushes were replaced with a high pressure spray nozzle that used water and an abrasive to clean the stud. This apparatus shared many of the same problems including requiring additional handling to put the studs in the horizontal position and being limited to cleaning one reactor stud at a time.
SUMMARY OF THE INVENTION
Briefly, the present invention provides a reactor stud cleaning apparatus for cleaning connector studs, nuts, and washers used to secure reactor heads on nuclear reactors. The cleaning apparatus is a self-contained unit having a housing that includes at least two independent sealable compartments allowing cleaning of two or more studs at a time. Each sealable compartment has a topside covering with a port that allows the reactor studs to be lowered into the apparatus keeping the longitudinal axis of the reactor stud maintained in a substantially vertical position. Inside the sealable compartments is a turntable for vertically mounting a reactor stud and for rotating the stud about its longitudinal axis. Brushes rotatably mounted inside the compartment are used to clean the reactor stud. The ability to keep the reactor studs in a vertical position decreases the handling required and therefore the safety risk associated with handling of the potentially radioactive studs.
Preferably, the apparatus also has a cleaning agent circulation system for circulating solvents or other cleaning agents over the reactor stud during cleaning.
The circulation system of the present invention stores cleaning agent in a sump. A pump is used to pump the cleaning agent from the sump to a spray nozzle where the agent is sprayed over the reactor stud during cleaning. The cleaning agent is then drained from the compartment and passed through a filter to remove contaminants before it is returned to the sump for reuse. Spent cleaning agent can be drained from the sump and disposed of according to appropriate hazardous waste regulations. The cleaning agent circulation system enhances the cleaning of the reactor studs, while the amount of waste generated is minimized by filtering and reusing the cleaning agent.
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patent: 8-015491 (1996-01-01), None
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Griffin John S.
Mikulenka William G.
Plunkett Alan W.
Bracewell & Patterson L.L.P.
Carone Michael J.
Keith Jack
STP Nuclear Operating Company
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