[en] This invention generally concerns an automatic control and locking stop valve. Specifically it relates to the use of such a valve in a nuclear reactor of the type containing absorber elements supported by a fluid and intended for stopping the reactor in complete safety

[en] A self-actuating, self-locking flow cutoff valve is described particularly suited for use in a nuclear reactor of the type which utilizes a plurality of fluid support neutron absorber elements to provide for the safe shutdown of the reactor. The valve comprises a substantially vertical elongated housing and an aperture plate located in the housing for the flow of fluid therethrough, a substantially vertical elongated nozzle member located in the housing and affixed to the housing with an opening in the bottom for receiving fluid and apertures adjacent a top end for discharging fluid. It is a particular feature of the present invention that the valve further includes a means for utilizing any increase in fluid pressure to maintain the cutoff sleeve in a closed position. It is another feature of the invention that there is provided a means for automatically closing the valve whenever the flow of fluid drops below a predetermined level. (Auth.)

[en] A valve, particularly suited for use in a nuclear reactor of the type which utilises a plurality of fluid support neutron absorber elements to provide for the safe shutdown of the reactor, comprises a vertical housing, an aperture plate and a vertical nozzle in the housing, with an opening in the bottom for receiving fluid and apertures for discharging fluid. Two sealing surfaces surround the nozzle above and below the apertures. Around the nozzle is a flow cutoff sleeve having openings in its upper end. The valve is closed when the sleeve drops and sealing surfaces mate with the nozzle sealing surfaces. The surfaces are such that any increase in pressure then only tends to close the valve more tightly. In normal operation fluid flow holds the sleeve up so that a plate attached to the sleeve partially blocks the plate and provides a pressure drop acting to hold the sleeve up. A weighted closing member can be released to force the sleeve to close. (author)

[en] A self-actuating, self-locking flow cutoff valve particularly suited for use in a nuclear reactor of the type which utilizes a plurality of fluid support neutron absorber elements to provide for the safe shutdown of the reactor. The valve comprises a substantially vertical elongated housing and an aperture plate located in the housing for the flow of fluid therethrough, a substantially vertical elongated nozzle member located in the housing and affixed to the housing with an opening in the bottom for receiving fluid and apertures adjacent a top end for discharging fluid. The nozzle further includes two sealing means, one located above and the other below the apertures. Also located in the housing and having walls surrounding the nozzle is a flow cutoff sleeve having a fluid opening adjacent an upper end of the sleeve, the sleeve being moveable between an upper open position wherein the nozzle apertures are substantially unobstructed and a closed position wherein the sleeve and nozzle sealing surfaces are mated such that the flow of fluid through the apertures is obstructed. It is a particular feature of the present invention that the valve further includes a means for utilizing any increase in fluid pressure to maintain the cutoff sleeve in a closed position. It is another feature of the invention that there is provided a means for automatically closing the valve whenever the flow of fluid drops below a predetermined level

[en] A flow cutoff valve that is particularly suited for use with fluid-supported neutron absorber elements is described. The valve comprises a vertical elongated housing containing an apertured plate, an elongated nozzle member, and a flow cutoff sleeve. The nozzle has an opening in the bottom for receiving fluid and apertures near the top end for discharging fluid, as well as two sealing surfaces located above and below the apertures. The flow cutoff sleeve has walls surrounding the nozzle, a fluid flow opening at its upper end, and two sealing surfaces. The sleeve may move between an upper open position where the nozzle apertures are unobstructed, and a lower position in which the sleeve and nozzle sealing surfaces are mated and the flow of fluid through the nozzle apertures is blocked. Once the valve is in a closed position an increase in fluid pressure will keep it closed

[en] A method is described of cleaning a fuel assembly including surfaces thereof prior to decladding, each assembly surface contaminated with a radioactive alkali metal and comprising a plurality of pressurized metallic fuel pins containing a spent fissible material, the method comprising the sequential steps of: (a) placing the fuel assembly in a sealed chamber; (b) passing a heated, inert gas through the chamber to heat the fuel assembly to a temperature sufficient to cause volatilization of the alkali metal but insufficient to rupture the pressurized metal pins; (c) evacuating the chamber to a pressure of less than 0.5 mm of Hg to further enhance volatilization and removal of the alkali metal and maintaining the chamber at that pressure until the decay heat of the fissile materials causes the temperature of the fuel assembly to increase to a level which would be detrimental to the integrity of the metal pins; (d) cooling the fuel assembly by passing a cool, inert gas through the chamber to reduce the temperature of the fuel assembly to a desired level; (e) repeating the evacuation and cooling steps as required to insure removal of substantially all of the radioactive alkali metal from the assembly surface; and (f) recovering the cleaned fuel assembly from the chamber

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No abstract available

[en] Full text: ⁹⁹Tc^m(V)-DMSA [DMSA(V)] has shown promise in brain tumour imaging. This study aimed to assess the role of DMSA(V) brain SPET in glioma for: (1) predicting the histopathological grade of malignancy, (2) monitoring response to therapy and (3) discriminating recurrent tumour from post-radiotherapy necrosis. Twenty-three patients (pts) (14 men, 9 women) of mean age 57 years (range 20-79) were referred with a lesion on CT/MRI (14 new presentations, 5 known and 4 suspected tumour recurrence). Up to 555 MBq of ⁹⁹Tc^m(V)DMSA were administered and SPET was acquired at 3 h. Tumour uptake ratio (UR) was calculated by the ratio of activity in the tumour to a region in the contralateral brain. All 19 pts with known tumour showed DMSA(V) uptake. The 14 pts with new tumours (10 grade IV, I grade III, 2 grade II and 1 necrotic tumour) had a pre-therapy mean UR of 7.7 (range 2.8-13.6). The 3 lower-grade tumours were scattered widely within this range. Four pts completed radiotherapy and returned for a post-therapy scan, where the UR was less than the pre-therapy UR in 2, unchanged in 1 and greater in 1. The 5 known recurrent tumours had a mean UR of 13.5 (range 7.3-24.9). In the 4 pts with suspected recurrence, the DMSA(V) scan result agreed with clinical course or PET in 3 but was falsely positive in 1. In summary,⁹⁹Tc^m(V)-DMSA: (1) showed uptake in all known glial cell tumours in this series, however the UR did not correlate with the histopathological grade; (2) may be useful for discriminating tumour recurrence from post-radiotherapy necrosis; and (3) may have a role in predicting post-therapy prognosis