Claims
- 1. An improved method of draining down contained reactor-coolant water from the inverted vertical U-tubes of at least one vertical-type steam generator in which the upper inverted U-shaped ends of said tubes are closed and the lower ends thereof are open, said steam generator having a channel head at its lower end including a vertical dividing wall defining a primary water inlet side and a primary water outlet side of the generator, said steam generator having chemical volume control system means and residual heat removal system means, and said steam generator being part of a nuclear-powered steam generating system wherein said reactor-coolant water is normally circulated from and back into the reactor via a loop comprising said steam generator and inlet and outlet conduits connected to the lower end of said steam generator, and said reactor being in communication with pressurizer means and comprising the steps of introducing a gas which is inert to the system and which is under pressure above atmospheric pressure into at least one of the downwardly facing open ends of each of said U-tubes from below the tubesheet in which the open ends of said U-tubes are mounted adjacent the lower end of said steam generator while permitting said water to flow out from said open ends of the U-tubes, the improvement in combination therewith for substantially increasing the effectiveness and efficiency of such water removal from said tubes, which improved method comprises the additional steps of:
- (A) determining the parameters effecting a first average volumetric rate of removal for a predetermined period of time, said period of time being substantially coincident with the period of time in step (B), infra, of the reactor-coolant water from said inverted vertical U-tubes, the specific unit for said first average volumetric rate expressing properties identical with the properties expressed in a second average volumetric rate maintained in a later mentioned step;
- (B) determining the parameters effecting a second average volumetric rate of introduction of said gas, which is under said pressure above atmospheric pressure and which is introduced into at least one of the downwardly facing open ends of each of said U-tubes, at a predetermined value and at least for a portion of the period of time during said draining down in which the reactor-coolant water level, in the portion of the reactor cooling system external to said tubes and including said pressurizer means, is lowered to about the elevation of said tubesheet, said at least one of the downwardly facing open ends of each of said U-tubes being in communion with said primary water outlet side in the channel head of said steam generator and effecting a standing water column therein; and
- (C) maintaining a ratio of said second average volumetric rate of introduction of said gas to said first average volumetric rate of removal of the reactor-coolant water from said inverted vertical U-tubes in the range from about 1.2:1 to about 0.8:1;
- said improved method characterized by the fact that the maintenance of said ratio effectively eliminates the formation of a gas-liquid interface juxtaposed the underside of said tubesheet, which gas-liquid interface formation would otherwise substantially impede or otherwise prevent the efficient and effective introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes.
- 2. The method according to claim 1, wherein said gas is nitrogen.
- 3. The method according to claim 2, wherein said ratio of said second average volumetric rate of introduction of said gas to said first average volumetric rate of removal of the reactor-coolant water is maintained in the range of from about 1.1:1 to about 0.9:1.
- 4. The method according to claim 3, wherein said ratio is maintained at about 1:1.
- 5. The method of claim 1 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals.
- 6. The method of claim 3 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals.
- 7. The method of claim 4 wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals.
- 8. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of as introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein:
- t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ;
- t.sub.1 '=(.sqroot.p.sub.1 /.sqroot.p.sub.2)t.sub.1 wherein p.sub.3 is a second preselected pressure of gas introduction which is in excess of p.sub.1, but is less than the critical pressure (p.sub.t) of said gas;
- p.sub.t .apprxeq.0.53p.sub.1 and p.sub.t is less than p.sub.3, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and
- t.sub.2 '=(1-t') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period.
- 9. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein:
- t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure to beneath said tubesheet of p.sub.1 ;
- t.sub.1 '=(4.472/.sqroot.p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1, but is less than the critical pressure (p.sub.t) of said gas;
- p.sub.t .apprxeq.0.53p.sub.2 and p.sub.t is less than ps, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and
- t.sub.2 '=(2-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period.
- 10. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig, and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off ranging from about 0.075:1 to about 0.05:1.
- 11. The method according to claim 3, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig, and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off ranging from about 0.07:1 to about 0.057:1.
- 12. The method according to claim 4, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes at a pressure of about 20 psig. and wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about 0.0634:1.
- 13. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ',and wherein:
- t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ;
- t.sub.1 '=(p.sub.1 /p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1. and is greater than the critical pressure (p.sub.t) of said gas;
- p.sub.t .apprxeq.0.53p.sub.2 and p.sub.t is greater than p.sub.3 , wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and
- t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period.
- 14. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio of gas introduction pulse time-on to gas introduction pulse time-off of about t.sub.1 ':t.sub.2 ', and wherein:
- t.sub.1 =the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure to beneath said tubesheet of p.sub.1 ;
- t.sub.1 '=(20/p.sub.2)t.sub.1 wherein p.sub.2 is a second preselected pressure of gas introduction which is in excess of p.sub.1, and is greater than the critical pressure (p.sub.t) of said gas;
- P.sub.1 .apprxeq.0.53p.sub.2 and p.sub.t is greater than p.sub.3, wherein p.sub.3 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and
- t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period.
- 15. The method according to claim 1, wherein said ratio is maintained by the introduction of said gas into at least one of the downwardly facing open ends of each of said U-tubes wherein said introduction of said gas is intermittently and repetitively performed at periodic intervals at a ratio as introduction final pulse time-on to gas introduction final pulse time-off of about t.sub.21 ':t.sub.22 ',and wherein:
- t=the pulse time-on period derived from empirical determinations of the delivery rate at a first preselected gas introduction pressure, to beneath said tubesheet, of p.sub.1 ;
- t.sub.1 '=(.sqroot.p.sub.1 /.sqroot.p.sub.2)t.sub.1 wherein p.sub.2 is a second and intermediate preselected pressure of gas introduction which is in excess of p.sub.1 and less than p.sub.3 ;
- p.sub.t .apprxeq.0.53p.sub.2 is less than p.sub.4, wherein p.sub.t represents the critical pressure (p.sub.t) of said gas and wherein p.sub.4 equals the back pressure exerted by said standing water column in said channel head and said U-tubes in communion therewith; and
- t.sub.2 '=(1-t.sub.1 ') and represents the pulse time-off period, with t.sub.1 ' representing the pulse time-on period;
- t.sub.21 =t.sub.1 ';
- t.sub.21 '=(.sub.2 /p.sub.3)t.sub.21 wherein p.sub.3 is the final preselected pressure of gas introduction which is in excess of p.sub.2 ;
- p.sub.t '.apprxeq.0.53p.sub.3, p.sub.t ' is greater than p.sub.4 and represents the critical pressure (p.sub.t ') of said gas at introduction pressure ps;
- t.sub.22 '=(1-t.sub.21 ') and represents the final pulse time-off period, with t.sub.21 ' representing the final pulse time-on period.
- 16. The method according to claim 13, wherein p.sub.2 ranges upwards from said p.sub.t to about 400 psig.
- 17. The method according to claim 14, wherein p.sub.2 ranges upwards from said p.sub.t to about 400 psig.
- 18. The method according to claim 5, wherein said channel head has flow openings and wherein said gas is introduced via one of the flow openings for said water through the channel head adjacent to the lower end of said steam generator.
- 19. The method according to claim 5, wherein said gas is introduced through an opening in a manway attached to said channel head adjacent to the lower end of said steam generator.
- 20. The method according to claim 5, wherein said nuclear-powered steam generating system includes respective flow transmitters for detecting flow of said coolant water through said outlet conduit of each said steam generators, each said flow transmitter having a high-impulse reference tube and a low-impulse reference tube, both of which are attached to said outlet conduit of the steam generator, and wherein said gas is introduced via one of said flow transmitter impulse reference tubes associated with each said steam generator.
Government Interests
The invention herein described may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty therefor.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
3825060 |
Heller et al. |
Jul 1974 |
|
4261300 |
Cross et al. |
Apr 1981 |
|
4649019 |
Jawor |
Mar 1987 |
|