JPH02162288A - Neutron counter - Google Patents

Abstract

PURPOSE:To confirm integrity at any time at any place by forming a center electrode by coating the core wire of a neutron counter with a live zero radiation source having a long half-life period. CONSTITUTION:End plates 2a, 2b are mounted to both ends of an outer cylindri cal electrode 1 in an airtight manner and a signal wire pierces the insulating terminal 3b insulated from said electrode to be taken out to the outside. A center electrode 6 formed by coating a tungsten core wire with a live zero radiation source of <241>Am is used in the electrode 1. When high voltage is applied to said electrode 6, an ion pair is formed and the flow of an electrode ion of each polarity and an electron to become a signal pulse. The energy of the alpha-particle issued from the live zero radiation source is about 5.4MeV and the energy of the charged particle generated by the nuclear reaction of a neutron and boron trifluoride is about 3MeV and the pulses per one incident particle are almost same and both pulses can be measured without changing a measuring condition and, therefore, even in a case performing no pre- measurement as a neutron monitor, the pulses due to the alpha-particle are periodi cally measured to make it possible to confirm the device integrity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a neutron counter used for detecting neutrons.

[Conventional technology]

FIG. 2 is a longitudinal cross-sectional view showing a conventional neutron counter disclosed, for example, in Japanese Patent Publication No. 61-35657, and the following description will be made using a boron trifluoride proportional counter as an example.

In FIG. 2, l is a cylindrical cathode (hereinafter referred to as a cathode) which is an outer cylinder electrode, 2a and 2b are end plates airtightly attached to both ends of the cathode l, and 3a and 3b are end plates 2a and 2b. The insulated terminal 4 is installed approximately in the center of the insulated terminal 3.
The diameter of the core wire stretched on the central axis of the cathode 1 between a and 3b is 2
The anode is a center electrode made of a tungsten wire of 5 to 1100 u, and 5 is boron trifluoride (BF).

gas).

Next, the operation will be explained. A boron trifluoride proportional counter is a neutron detector that detects thermal neutrons (neutrons with an energy of about 0.025 eV).

Since neutrons themselves have no electric charge, they cause the following nuclear reactions to generate charged particles that have the ability to ionize.

凰'B +n (neutron) → FuLi” +α+2.3
MeV'Li'' −* 'Ll+0.48MeV(r)
'Li': When α particles and Li nuclei generated in an excited state nuclear reaction pass through BF and gas, each nucleus loses its energy while ionizing BF and gas. An anode 4 is stretched across the center of the l, and a high voltage is applied to form a strong electric field.
This charge causes the electrons to amplify the gas and create a pulse signal.

[Problem to be solved by the invention]

Conventional neutron counter tubes are configured as described above, so they must be calibrated periodically to accurately measure thermal neutrons, but normally this calibration is only possible if you have a standard source of neutrons. In addition, there was a problem in that it was not easy to ensure the integrity of the boron trifluoride proportional counter tube, which had not been used for a long time, by counting charges in pulses and accurately measuring neutrons.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a neutron counter whose health can be confirmed without having a standard neutron source.

(Means for Solving the Problem) A neutron counter according to the present invention has a core wire provided at the center of an outer cylindrical electrode whose interior is kept airtight, and a live zero radiation source with a long half-life is coated to form a center electrode. It was formed.

[For production]

The neutron counter in this invention uses a center electrode whose core wire is coated with a live zero source with a long half-life, so that alpha particles from the live zero source always generate a constant signal pulse. Therefore, the soundness can be easily confirmed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a longitudinal cross-sectional view showing one embodiment of the present invention. In Figure 1, the same or equivalent parts as in Figure 2 are denoted by the same reference numerals and redundant explanation is omitted. In Figure 0, 6 is a tungsten core wire, for example. "'Am's live zero radiation source is coated on the anode, and from this anode 6 live zero radiation source, approximately 5.4
MeV alpha particles are emitted with a half-life of 433 years.

Thus, the end plates 2a are airtightly attached to both ends of the outer cylinder which becomes the cathode 1.
, 2b are attached to form an airtight container, and a signal line is taken out to the outside through an insulated terminal 3b that is insulated from this airtight container.

In addition, the explanation of the operation is omitted as it is the same as the conventional example, but for the outer cylinder electrode, the tungsten core wire is
Since a center electrode coated with a live zero radiation source of m is used, when a high voltage is applied, ion pairs are generated by the reaction described below, and a flow of electric bridge heyons and electrons of each polarity occurs, resulting in a signal pulse.

BF2-+ BF3"+e- (w value is about 35 eV) Also, the energy of the α particles emitted from this "'Am live zero radiation source is about 5.4 MeV, and as a boron trifluoride proportional counter, it can be used as a neutron and 3 The energy of the charged particles produced by the nuclear reaction with boron fluoride is approximately 3 MeV,
The pulse per incident particle (neutron or α particle from a live zero radiation source) is of the same magnitude, and both pulses can be measured without changing the measurement conditions (applied voltage, discret setting voltage). Therefore, even when not being measured as a neutron monitor (when stored for a long period of time), the health of the 37 boron fluoride counter can be confirmed by periodically measuring the pulses caused by the α particles.

In the above embodiment, the outer tube electrode is used as a cathode and the center electrode is used as an anode. However, even if the outer tube bridge is used as an anode and the center electrode is used as a cathode, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the center electrode is formed by coating the core wire of the neutron counter tube with a live zero source (t41Am) having a long half-life, it can be operated without a standard neutron source. It has the effect of allowing you to confirm your gender anytime, anywhere.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a neutron counter according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing an example of a conventional neutron counter. 1 is an outer cylinder electrode, and 6 is a center electrode. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A center electrode is provided at the center of an outer cylinder electrode whose interior is kept airtight.
In a neutron counter tube that measures thermal neutrons by counting signal pulses generated by applying a high voltage between the outer cylindrical electrode and the center electrode, a live zero radiation source with a long half-life is connected to the center electrode as a core wire. A neutron counter tube characterized by being formed by coating.