Reactor water control method in BWR power plant, BWR power plant having low radioactivity concentration reactor water and fuel clad tube for BWR

• US 5,715,290 A
• Filed: 06/14/1994
• Issued: 02/03/1998
• Est. Priority Date: 07/01/1993
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hara, Teruo, Kondoh, Masayoshi, Uetake, Naohito, Asakura, Yamato, Akamine, Kazuhiko, Hosokawa, Hideyuki, Nagase, Makoto, Ohsumi, Katsumi, Yamane, Kouichi
• Primary Examiner(s): Gorgos, Kathryn L.
• Assistant Examiner(s): CARROLL, CHRISMAN DION
• Application Number:
  US08/260,472
• Time in Patent Office: 1,330 Days
• Field of Search: 376/305, 376/306, 376/416, 376/417, 376/267
• US Class Current: 376/306
• CPC Class Codes: G21C 17/0225 Chemical surface treatment, e.g. corrosion corrosion prevention in presence of water from scale removal or by modification of the properties of the liquid C02F5/00; inhibiting corrosion by adding corrosion inhibitors C23F11/00
• CPC Class Codes: G21C 19/307 specially adapted for liquids decontamination of liquids G21F9/04
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

In reactor water control for a BWR power plant during an operation cycle after loading new fuel rods in the BWR power plant, an operation is performed which accelerates deposition of crud on the fuel rods until the deposition amount of the crud on the fuel rods reaches a predetermined target value within the operation cycle concerned. After the deposition amount of the crud has reached the predetermined target value, the crud deposition accelerating operation is terminated, whereby even when loading new fuel rods such as Zr liner type fuel rods having a surface on which metal ion deposition has been difficult, radioactivity in the reactor water is efficiently reduced.

Claims

1. A reactor water control method for a BWR power plant comprising the steps of:

loading new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant;

performing a step of at least one of injecting iron crud in a high concentration into the reactor water, injecting a metal element having a low solubility into the reactor water, and shifting the pH of the reactor water to the alkaline side so as to accelerate deposition speed of at least one of the iron crud and metal element on the newly loaded fuel rods formed with Zr liner type fuel clad tubes at an initial stage in an operation cycle of the BWR power plant after loading the new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant until a deposition amount of at least one of the iron crud and the metal element on the newly loaded fuel rods formed with Zr liner type fuel clad tubes reaches a target value; and

terminating said step of at least one of injecting iron crud, injecting a metal element and shifting so as to terminate the acceleration of the deposition speed after the deposition amount of at least one of the iron crud and the metal element has reached the target value;

wherein the metal element having the low solubility is at least one element selected from the group consisting of Zr, Al, Nb, Y and Ti.

2. A reactor water control method for a BWR power plant according to claim 1, wherein the target value is set at a value of at least 30 μ

g/cm² as an average.

3. A reactor water control method for a BWR power plant comprising the steps of:

loading new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant;

performing the step of injecting iron crud in a high concentration and a metal element having a low solubility into the reactor water so as to accelerate deposition speed of the iron crud and the metal element on the newly loaded fuel rods formed with Zr liner type fuel clad tubes at an initial stage in an operation cycle of the BWR power plant after loading the new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant until a total amount of the injected iron crud and the metal element exceeds a value which is determined by a product of a target deposition amount of the iron crud and the metal element on the newly loaded fuel rods formed with Zr liner type fuel clad tubes per unit area multiplied by a value representing the entire surface area of the newly loaded fuel rods formed with Zr liner type fuel clad tubes; and

terminating the step of injecting after the total amount of the injected iron crud and the metal element has reached the value;

wherein the metal element having the low solubility is at least one element selected from the group consisting of Zr, Al, Nb, Y and Ti.

4. A reactor water control method for a BWR power plant according to claim 3, wherein a target of the iron crud and the metal element deposition amount is set at a value of at least 30 μ

g/cm² as an average.

5. A reactor water control method for a BWR power plant comprising the steps of:

loading new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant;

performing the step of controlling the pH of the reactor water in a range of more than 7 and less than 9 so as to accelerate deposition speed of crud contained in the reactor water on the newly loaded fuel rods formed with Zr liner type fuel clad tubes at an initial stage in an operation cycle of the BWR power plant after loading the new fuel rods formed with Zr liner type fuel clad tubes in the BWR power plant at least until a deposition amount of the crud on the newly loaded fuel rods formed with Zr liner type fuel clad tubes reaches a target value; and

terminating the controlling step and reducing the pH of the reactor water to less than 7 after the deposition amount of the crud has reached the target value.

6. A reactor water control method for a BWR power plant according to claim 5, wherein the target value is set at a value 30 μ

g/cm² as an average.