RU2235377C2 - Californium-252 base neutron source for monitoring nuclear reactor operation - Google Patents

Abstract

FIELD: nuclear engineering.

SUBSTANCE: proposed californium-252 base neutron source designed for controlling operation of nuclear reactor has capsules and core produced by immobilizing californium-252 in porous blank made of platinum or aluminum oxide. Capsules are made of steel resistant to corrosion by liquid sodium and capable of retaining its geometry and strength characteristics at detrimental radiation dose in nuclear reactor exceeding 30 shifts per atom.

EFFECT: enhanced reliability of neutron source capsules.

3 cl, 1 dwg

Description

The invention relates to nuclear engineering and can mainly be used in the manufacture of neutron radiation sources based on actinide elements, including for monitoring the operation of the reactor.

In connection with the ever-increasing requirements for the safety of nuclear reactors, there is a need to monitor the parameters of the neutron flux when recruiting the initial loading of the reactor, removing it from a subcritical state during fuel reloading and monitoring power during operation. These parameters are monitored by changing the neutron flux by sensors installed at the control points of the reactor. Initial calibration of these sensors should be carried out using a neutron source installed in the center of the reactor core.

This source must have strength classes not lower than C (E) 66546 in accordance with the classification according to the international standard IO 2919-80 (GOST 25926-90).

The material of the source capsules must be resistant to liquid sodium at a temperature of 400-500 ° C and maintain the geometric dimensions and strength characteristics at a damaging dose due to intensive neutron irradiation of at least 50 displacements per atom.

A known neutron source based on California-252 (US patent No. 3640888), consisting of an active core, which is obtained by vitrification of the emitter element, and a capsule in which it is placed and sealed. The active part contains no more than 30 μg of California. The capsule is made of corrosion-resistant steel type 12X18H10T.

The source did not find wide application, because in the process of exploitation, radiation destruction of the glass occurs, and in case of violation of the tightness of the shell, the radioactive element can migrate into the environment.

A known neutron source (US patent No. 3787321), the active part of which is obtained by spraying a salt of California nitrate-252 on the cold surface of the capacitor and subsequent operations associated with the formation of the core in a tablet. The active part of such a source contains no more than 200 μg per 1 cm of length.

The above neutron sources have high strength classes C (E) 66546 according to ISO-2919-80, but not high enough content of California-252.

Closest to the claimed technical essence is a neutron source containing the active part and two shells. The active part is obtained by impregnating the porous matrix with a solution of California-252 and subsequent fixation of the emitting element by heat treatment (RF patent No. 2097856). The core contains up to 500 μg / mm ³ emitter. Capsules are made of steel 12X18H10T.

A source with such an active part provides a neutron flux (≥10 ⁹ s ^-1 ), which is sufficient for continuous monitoring of the operation of an atomic reactor.

The capsules of the neutron source, taken as a prototype, like all others described in analogues, are made of steels that retain their strength characteristics with a damaging radiation dose of not more than 30 displacements per atom.

The proposed neutron source, suitable for operation in the core of a nuclear reactor, contains two capsules made of corrosion-resistant to liquid sodium and retaining its geometric and strength characteristics with a damaging radiation dose in a nuclear reactor of more than 50 displacements per atom and core sealed in capsule, which is made by impregnating a porous preform of aluminum oxide or platinum with a solution of California-252, fixing it by heat treatment at a temperature of 800-1200 ° C.

Ferritic-martensitic steel, for example 1X13M2BFR, or austenitic steel with increased resistance to radiation swelling EP172 (08X16H15MZBR) or ChS68 (03X16N15M2G2TFR) are used as capsule material.

These steels have great resistance to radiation swelling and radiation creep, retain their mechanical properties and geometric dimensions of structural elements with a damaging dose in the nuclear reactor up to 140 displacements per atom.

The drawing shows a neutron source of California-252, where 1 is the outer capsule, 2 is the active core, 3 is the inner capsule, 4 is the cork.

Claims (3)

1. A neutron source based on California-252 to control the operation of an atomic reactor, containing capsules and a core obtained by fixing California-252 in a porous preform of platinum or aluminum oxide, and the capsules are made of steel that is corrosion resistant to liquid sodium and retains their geometric and strength characteristics with a damaging radiation dose in a nuclear reactor of more than 30 displacements per atom. 2. The source according to claim 1, in which ferritic-martensitic steels are used as the material of the capsule. 3. The source according to claim 1, in which austenitic steels EP-172 (08X16H15MZBR) or ChS-68 (03X16H15M2G2TFR) are used as the capsule material.