CN104407371A - System and method for rapidly detecting concentration of 210Po in molten lead bismuth alloy - Google Patents

Abstract

The invention relates to a system and method for rapidly detecting the concentration of 210Po in a molten lead bismuth alloy. By measuring a characteristic gamma ray generated during 210Po decay, the content of 210Po in the molten lead bismuth alloy is quantitatively analyzed. The system and the method which are simple in principle and high in operability are provided for analyzing and detecting the concentration of 210Po, and the system and the method are applicable to rapid detection on the concentration of 210Po in a coolant of a fast reactor primary coolant circuit taking molten lead bismuth alloy as a coolant.

Description

In a kind of liquid lead bismuth alloy 210the rapid detection system of Po concentration and method

Technical field

The present invention relates to a kind of analysis detection system and method, by gamma-rays energy spectrum analysis, realize in liquid lead bismuth alloy ²¹⁰the quick detection of Po concentration.

Background technology

Be that in the fast neutron reactor of cooling medium, neutron irradiation bismuth can produce at liquid lead bismuth alloy ²¹⁰po, due to ²¹⁰po has pole toxicity, in reactor operation or between the date of retirement, needs in reactor pressure vessel and primary Ioops ²¹⁰po carries out extraction and isolation, produces in liquid lead bismuth alloy thus ²¹⁰the analysis of Po detects demand.

²¹⁰po has very strong α radiation, and the half life period is 138.3 days. ²¹⁰the traditional analysis detection method of Po comprises calorimetry, alpha energy spectrum or α counting method.Calorimetry is suitable for the little but sample that heat release amount is large of volume, in sample ²¹⁰the radioactivity of Po needs to reach Curie's level, could obtain reasonable measuring accuracy, and due to the time reaching stable thermal equilibrium longer, calorimetry measure ²¹⁰po can not meet the testing requirement of express-analysis.The sensitivity that alpha energy spectrum or α counting method are measured is very high, but ²¹⁰the Po half life period is shorter, and specific activity is comparatively large, and therefore alpha energy spectrum or α counting method are generally used for measuring ²¹⁰the sample that Po content is extremely low.And the penetration capacity of α particle is weak, can not block between testing sample and detector probe, must carry out the measurement of closely open type, therefore alpha energy spectrum or α counting method are surveyed ²¹⁰also there is the problem that detector easily pollutes in Po.

Summary of the invention

The object of the invention is to: overcome the deficiencies in the prior art, provide in a kind of liquid lead bismuth alloy ²¹⁰the rapid detection system of Po concentration and method, realize in liquid lead bismuth alloy ²¹⁰the quick detection of Po concentration.

The technology of the present invention solution:

1, in a kind of liquid lead bismuth alloy ²¹⁰the rapid detection system of Po concentration, its system features is to comprise: sample tap, press, gamma detector, corresponding electronics equipment, data handling system; Adopt press to suppress after the sample cooling that sample tap obtains, the thin slice after compacting detects before being arranged on detector, and detectable signal, through corresponding electronics equipment and data handling system process, is obtained in liquid lead bismuth alloy by analytical calculation ²¹⁰po concentration.

2, in a kind of liquid lead bismuth alloy ²¹⁰the method for quick of Po concentration, its method characteristic is to comprise the following steps:

(1) sample a certain amount of liquid lead bismuth alloy and make its natural cooled and solidified;

(2) with press, the solid lead bismuth alloy after solidifying is pressed into the uniform sheet of certain thickness and size;

(3) before solid lead bismuth alloy thin slice being arranged on gamma detector probe;

(4) in gamma detector detection solid lead bismuth alloy thin slice ²¹⁰the Characteristic γ ray that Po launches;

(5) detectable signal is after electronics equipment and data handling system carry out signal transacting and data processing, obtains gamma intensity;

(6) computational analysis obtains in liquid lead bismuth alloy ²¹⁰po content.

The sampling amount of described step (1) liquid lead bismuth alloy is 5g ~ 10g;

The solid lead bismuth alloy sheet thickness that described step (2) is suppressed is 0.5mm;

The installation of described step (3) makes the side of the non-detection window of gamma detector and sample chamber all be surrounded by lead shield layer, reduces gamma-rays background;

Described step (4) is measured ²¹⁰the energy of Po Characteristic γ ray is 803.1keV.

The present invention's advantage is compared with prior art:

(1) ²¹⁰the gamma activity branching ratio of Po is very low, only about 100,000/, therefore ²¹⁰the gamma-ray measurement of Po is usually left in the basket.In the plumbous bismuth fast reactor primary Ioops coolant media, there is high relative contents ²¹⁰po concentration, makes to determine by measuring Characteristic γ ray intensity ²¹⁰po concentration becomes possibility.Liquid lead bismuth alloy has that temperature is high, density is large, good, the low-melting feature of thermal conductivity, directly measures in liquid lead bismuth alloy ²¹⁰the Characteristic γ ray intensity of Po, need to maintain liquid lead bismuth alloy temperature at sample chamber design heating and thermal insulation layer, with gamma detector particularly semi-conductor type gamma detector need low temperature environment contradiction, and sample chamber limited space needs additional shielding, also makes directly to measure in liquid lead bismuth alloy ²¹⁰the Characteristic γ ray intensity difficulty of Po.In addition liquid lead bismuth alloy viscosity is large, easily stains sampling receptacle and forms fixing background.

For this reason, present invention employs after the cooling of liquid lead bismuth alloy, be pressed into certain thickness Solid Lead bismuth alloy thin slice with press, by what launch in detection Solid Lead bismuth alloy thin slice ²¹⁰po Characteristic γ ray intensity, obtains in Solid Lead bismuth alloy ²¹⁰po concentration.A kind of benefit measuring Solid Lead bismuth alloy thin slice is not easy to stain sample chamber and instrument forms fixing background, and the low compacting solid lead bismuth alloy thin slice that makes of Solid Lead bismuth alloy hardness is easy to realize, be pressed into thin slice and can reduce lead bismuth alloy to gamma-ray self-absorption, improve measuring accuracy.

(2) because calorimetry, alpha energy spectrum or α counting method are surveyed ²¹⁰the limitation of Po, one of the present invention is used in liquid lead bismuth alloy ²¹⁰the system and method that the express-analysis of Po concentration detects, by rational sample pre-treatments technological design, and utilizes gamma detector to measure ²¹⁰the Characteristic γ ray that Po decay produces, realizes in liquid lead bismuth alloy ²¹⁰the quick detection of Po.

(3) principle of the invention is simple; Analysis process is short, analysis speed is fast, and analysis precision is high; Be applicable in plumbous bismuth fast reactor primary Ioops coolant media ²¹⁰the quick detection of Po concentration, being also applicable to liquid lead bismuth alloy is in ADS system (accelerator-driven sub-critical system) the primary Ioops coolant media of cooling medium ²¹⁰the quick detection of Po concentration.

Accompanying drawing explanation

Fig. 1 is the composition frame chart of present system and the realization flow figure of the inventive method.

Embodiment

As shown in Figure 1, present system is containing following ingredient:

(1) sample tap, sample tap is for obtaining primary sample;

(2) press, carries out compression process to primary sample after cooling;

(3) gamma detector, is used for detecting gamma-rays;

(4) electronics equipment, is used for carrying out pre-service and process to detectable signal;

(5) data handling system, is used for obtaining data and process data, obtains gamma intensity.

As shown in Figure 1, realization flow of the present invention is as follows:

(1) sample a certain amount of liquid lead bismuth alloy and make its natural cooled and solidified;

(2) with press, the solid lead bismuth alloy after solidifying is pressed into the uniform sheet of certain thickness and size;

(3) before solid lead bismuth alloy thin slice being arranged on gamma detector probe;

(4) in gamma detector detection solid lead bismuth alloy thin slice ²¹⁰the Characteristic γ ray that Po launches;

(5) detectable signal is after electronics equipment and data handling system carry out signal transacting and data processing, obtains gamma intensity;

(6) computational analysis obtains in liquid lead bismuth alloy ²¹⁰po content.

Embodiment 1: provide the specific embodiment of the present invention citing below.

(1) use standard gamma source to carry out energy calibration and efficiency calibration to gamma detector, obtain near 803.1keV, detector efficiency is 9.6%;

(2) from liquid lead bismuth alloy vessel, take a morsel liquid lead bismuth alloy on stainless steel metal plate, treat its natural cooled and solidified, claim its quality to be 8.2g;

(3) with press, the solid lead bismuth alloy after solidifying is pressed into the uniform sheet of 0.5mm thickness, the thin slice of 0.5mm thickness can ensure ²¹⁰the Characteristic γ ray that Po launches fully penetrates;

(4) solid lead bismuth alloy thin slice is arranged on gamma detector probe;

(5) gamma spectrum measures the gamma intensity of 803.1keV in solid lead bismuth alloy thin slice, within 600 seconds, detects gamma ray counting 1126;

(6) calculate in liquid lead bismuth alloy ²¹⁰po content, computing formula is as follows:

$A\left(\mathrm{Po}_{210}\right)=\frac{I\left(\mathrm{\γ}\right)}{T\left(\mathrm{BR}\right)*\mathrm{\ϵ}\left(\mathrm{\γ}\right)}*\frac{1}{t}*\frac{M}{\mathrm{\λ}*\mathrm{NA}}*\frac{1}{m}$

In formula,

A ( ²¹⁰po)---in sample ²¹⁰the mass percent of Po, dimension is 1;

I (γ)---detect gamma-ray counting, dimension is 1;

T (BR)--- ²¹⁰the gamma activity branching ratio of Po, dimension is 1;

ε (γ)---gamma detector used, to gamma-ray detection efficiency, has considered the intrinsic detection efficiency of space exploration efficiency and detector, and dimension is 1;

T---detection time, dimension is second (s);

λ---disintegration constant, represents one ²¹⁰there is the probability decayed in Po, dimension is s within the unit interval ^-1;

M---molal weight, refers to unit amount of substance ²¹⁰the quality that Po has, dimension is gmol ^-1;

NA---Avogadro constant (Avogadro's constant, symbol: NA), refers to 0.012 kilogram ¹²comprise in C ¹²the atomic quantity of C, gets 6.023 × 10 during general calculating ²³, dimension is mol ^-1;

M---liquid lead bismuth alloy sampling quality, dimension is gram (g).

By t=600s, I (γ)=1126, T (BR)=1.1*10 ^-5, ε (γ)=9.6%, λ=5.8*10 ^-8s ^-1, M=210gmol ^-1, NA=6.023 × 10 ²³mol ^-1, m=8.2g brings above-mentioned computing formula into, obtains in sample ²¹⁰the mass percent A of Po ( ²¹⁰po) be 1.3*10 ^-7%.

Embodiment 2: provide the precision estimation that the present invention applies in plumbous bismuth fast reactor primary Ioops coolant media below.

(1) after the stable operation of plumbous bismuth fast reactor in primary Ioops coolant media ²¹⁰the gross activity activity of Po is about 10 ¹⁴bq (there is some difference for the plumbous bismuth fast reactor of different neutron-flux density and scale);

(2) plumbous bismuth fast reactor liquid lead bismuth alloy cooling medium loading amount about 1000 tons, provides according to step 1 ²¹⁰po gross activity activity, in liquid lead bismuth alloy ²¹⁰the mean radio concentration about 10 of Po ⁵bq/g;

(3) sample volume calculates according to 10g, ²¹⁰the branching ratio of Po gamma decay is 100,000/, estimate to obtain the average transmitting per second of 10g liquid lead bismuth alloy 10 photons;

(4) for NaI crystal-type gamma ray probe, the detection efficiency of gamma detector, after consideration steric effect and intrinsic conversion efficiency, is estimated according to 10%;

(5) 10 minutes are measured to sample, about 600 countings can be obtained, the statistical error about 4% of measurement count.

Claims (6)

1. in a liquid lead bismuth alloy ²¹⁰the rapid detection system of Po concentration, is characterized in that comprising: sample tap, press, gamma detector, corresponding electronics equipment, data handling system; Adopt press to suppress after the sample cooling that sample tap obtains, the thin slice after compacting detects before being arranged on detector, and detectable signal, through corresponding electronics equipment and data handling system process, is obtained in liquid lead bismuth alloy by analytical calculation ²¹⁰po concentration.

2. in a liquid lead bismuth alloy ²¹⁰the method for quick of Po concentration, is characterized in that comprising the following steps:

(1) sample a certain amount of liquid lead bismuth alloy and make its natural cooled and solidified;

(2) with press, the solid lead bismuth alloy after solidifying is pressed into the uniform sheet of certain thickness and size;

(3) before solid lead bismuth alloy thin slice being arranged on gamma detector probe;

(4) in gamma detector detection solid lead bismuth alloy thin slice ²¹⁰the Characteristic γ ray that Po launches;

(5) detectable signal is after electronics equipment and data handling system carry out signal transacting and data processing, obtains gamma intensity;

(6) computational analysis obtains in liquid lead bismuth alloy ²¹⁰po content.

3. in liquid lead bismuth alloy according to claim 2 ²¹⁰the method for quick of Po concentration, is characterized in that: the sampling amount of described step (1) liquid lead bismuth alloy is 5g ~ 10g.

4. in liquid lead bismuth alloy according to claim 2 ²¹⁰the method for quick of Po concentration, is characterized in that: the solid lead bismuth alloy sheet thickness that described step (2) is suppressed is 0.5mm.

5. in liquid lead bismuth alloy according to claim 2 ²¹⁰the method for quick of Po concentration, is characterized in that: the installation of described step (3) makes the side of the non-detection window of gamma detector and sample chamber all be surrounded by lead shield layer.

6. in liquid lead bismuth alloy according to claim 2 ²¹⁰the method for quick of Po concentration, is characterized in that: described step (4) is measured ²¹⁰the energy of Po Characteristic γ ray is 803.1keV.