US4293382A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of starting up a nuclear reactor
Assignee: Hitachi Ltd
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Filing: 1978-08-29
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Granted: 1981-10-06
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Expires: 1998-08-29
Abstract
Abstract At the time of starting up a nuclear reactor, the concentration of oxidizing substance in a cooling water in a reactor pressure vessel is decreased by evacuating the pressure vessel or replacing air in the vessel with an inert gas for a long time, below a predetermined level before the cooling water is heated to a temperature of 150° C., thereby preventing the occurrence of stress corrosion cracking.
Inventors
- 👤 Katsumi Ohsumi
- 👤 Minoru Miki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 22:05
CPC Classifications
G; G21; G21C; G21C19/00; G21C19/28; G21C7/00; Y; Y02; Y02E; Y02E30/00; Y02E30/30
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
77 words
A method of starting-up a nuclear reactor having a reactor pressure vessel conaining cooling water therein having an oxygen content greater than 5 ppm and a fission mass in a non-critical condition comprising the steps of reducing the oxygen concentration in the cooling water of the reactor pressure vessel to a concentration less than 0.5 ppm, causing the fission mass of the nuclear reactor to become critical, and raising the water temperature to at least 150° C.
Claim 2
Independent Claim
77 words
A method of starting-up a nuclear reactor having a reactor pressure vessel conaining cooling water therein having an oxygen content greater than 5 ppm and a fission mass in a non-critical condition comprising the steps of reducing the oxygen concentration in the cooling water of the reactor pressure vessel to a concentration less than 0.5 ppm, causing the fission mass of the nuclear reactor to become critical, and raising the water temperature to at least 150° C.
Claim 3
Dependent Claim
27 words
A method as set forth in claim 1, wherein said step of reducing the oxygen concentration includes a step of evacuating the interior of the pressure vessel.
Claim 4
Dependent Claim
30 words
A method as set forth in claim 1, wherein said step of reducing the oxygen concentration includes a step of replacing air in the pressure vessel with an inert gas.
Claim 5
Dependent Claim
18 words
A method as set forth in claim 1, wherein the oxygen concentration is reduced to about 0.2 ppm.
Claim 6
Dependent Claim
33 words
A method as set forth in claim 1, wherein the step of raising the water temperature to at least 150° C. is partially effected prior to causing the fission mass to become critical.
Claim 7
Dependent Claim
32 words
A method as set forth in claim 5, wherein the step of raising the water temperature to at least 150° C. is effected prior to causing the fission mass to become critical.
Claim 8
Dependent Claim
32 words
A method as set forth in claim 1, wherein the step of causing the fission mass to become critical is effected prior to raising the water temperature to at least 150° C.
Claim 9
Independent Claim
40 words
A method as set forth in one of claims 2, 3 or 1, further comprising the step of heating the cooling water in the pressure vessel to a predetermined value before the start of nuclear reaction in the nuclear reactor.
Claim 10
Dependent Claim
60 words
A method as set forth in claim 1, wherein the nuclear reactor is a boiling-water nuclear reactor of an electric power plant with a turbine connected to the nuclear reactor to be driven by steam generated in the reactor and with a condenser connected to the turbine, and starting up the electric power plant by starting up the nuclear reactor.
Claim 11
Dependent Claim
40 words
A method as set forth in claim 9, wherein said step of reducing the oxygen concentration includes a step of evacuating the pressure vessel of the nuclear reactor by communicating the pressure vessel with the condenser being kept in vacuum.
Claim 12
Dependent Claim
30 words
A method as set forth in claim 9, wherein said step of reducing the oxygen concentration includes a step of replacing air in the pressure vessel with an inert gas.
Claim 13
Dependent Claim
33 words
A method as set forth in claim 9, further including a step of heating the cooling wqter in the pressure vessel to a predetermined value of temperature before the start of nuclear reaction.
Claim 14
Dependent Claim
31 words
A method as set forth in claim 12, wherein said heating of the cooling water is effected by the circulation of the cooling water in the pressure vessel by a pump.
Claim 15
Dependent Claim
17 words
A method as set forth in claim 9, wherein the oxygen is reduced to about 0.2 ppm.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-10-05 | 1985-04-06 | 1985-10-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-05 | 1989-04-06 | 1989-10-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-05 | 1993-04-06 | 1993-10-06 | $7700.00 | Window Closed / Lapsed |