Shaft-sealing system for nuclear turbines

Claim 2

In a steam turbine subject to receiving contaminated steam in a closed steam and feedwater cycle and having at least one highpressure packing for sealing a turbine section operating above atmospheric pressure and at least one low-pressure packing for sealing a turbine section operating below atmospheric pressure, said packings defining a plurality of axially spaced chambers between groups of packing teeth forming close clearances with the a, each of said packings having an outermost end communicating with the atmosphere through one of said clearances, a noncontaminating shaft seal system for one of said packings comprising: first means including an exhauster system maintaining a first clean leakoff packing chamber at subatmospheric pressure adjacent said outermost end of the packing, and communicating with the atmosphere, second means maintaining a second steam return chamber at a subatmospheric pressure, said steam return chamber also communicating with the turbine cycle steam, and third means generating clean sealing steam at a pressure above atmospheric and supplying it to a third packing chamber between the first and second chambers, said clean steam generating means comprising an evaporator supplied with uncontaminated water and heated by steam extracted from said closed steam and feedwater cycle, whereby a portion of the generated clean steam flows toward the turbine and a portion is drawn along with air leaking inward from the outermost end of the packing through said exhauster system.

Claim 3

The combination according to claim 1, wherein said evaporator comprises a submerged coil connected at one end to a steam extraction line and at the other end to a tank draining to a lower pressure point in the steam and feedwater cycle.

Claim 4

The combination according to claim 1, wherein said steam return chamber is disposed in said low-pressure packing and communicates directly with said low-pressure turbine section.

Claim 5

In a steam turbine subject to receiving radioactive steam from a boiling water reactor and in a closed cycle and having shaft packing defining a plurality of axially spaced packing chambers between groups of packing teeth forming close clearances with the shaft, a noncontaminating shaft sealing system comprising: at least one high pressure packing having at least the following packing chambers in succession from the outer end of the packing, a. a subatmospheric clean steam leakoff chamber, b. a clean steam supply chamber maintained above atmospheric pressure, c. a subatmospheric pressure contaminated steam return chamber, at least one low-pressure packing having at least the following packing chambers in succession from the outer end of the packing, a. a subatmospheric clean steam leakoff chamber, b. a clean steam supply chamber maintained above atmospheric pressure, a submerged tube steal seal evaporator having a clean water supply source, first conduit means arranged to supply said submerged tube evaporator with extraction steam from the turbine, a drainage tank for collecting condensed water from said submerged tube evaporator, means controlling the flow of steam from said evaporator to said clean steam supply chambers and arranged to hold the pressure therein substantially constant, means connecting said return chamber of said high-pressure packing to a subatmospheric point in the cycle, and a leakoff steam exhaust system connected to withdraw a mixture of air and steam from said clean leakoff chambers and vented to the atmosphere.

Claim 6

In a steam turbine subject to receiving radioactive steam from a boiling water reactor and in a closed cycle and having shaft packing defining a plurality of axially spaced packing chambers between groups of packing teeth forming close clearances with the shaft, a noncontaminating shaft sealing system comprising: at least one high pressure packing having at least the following packing chambers in succession from the outer end of the packing, a. a subatmospheric clean steam leakoff chamber, b. a clean steam supply chamber maintained above atmospheric pressure, c. a subatmospheric pressure contaminated steam return chamber, at least one low-pressure packing having at least the following packing chambers in succession from the outer end of the packing, a. a subatmospheric clean steam leakoff chamber, b. a clean steam supply chamber maintained above atmospheric pressure, a submerged tube steal seal evaporator having a clean water supply source, first conduit means arranged to supply said submerged tube evaporator with extraction steam from the turbine, a drainage tank for collecting condensed water from said submerged tube evaporator, means controlling the flow of steam from said evaporator to said clean steam supply chambers and arranged to hold the pressure therein substantially constant, means connecting said return chamber of said high-pressure packing to a subatmospheric point in the cycle, and a leakoff steam exhaust system connected to withdraw a mixture of air and steam from said clean leakoff chambers and vented to the atmosphere.

Claim 7

The combination according to claim 1, wherein seal system for said packing also includes a high-pressure steam return chamber disposed adjacent to and on the turbine section side of said second steam return chamber, said high-pressure chamber being connected to a point in said closed steam and feedwater cycle to maintain the pressure therein between that of said second steam return chamber and that of the sectIon.