RU2713924C1 - Method of reproducing test standards for large-size objects on research reactors - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to a method for reproducing setpoints neutron fluence (F_ni), and the exposure dose of gamma-radiation (D_ni). Method is based on superposition of radiation fields from reactor and neutron converters to gamma quanta, determination of fluence of neutrons (F) with energies of more than 0.1 MeV and exposure dose (D) of gamma-quanta (object loading parameters) in the area of bilateral irradiation object selection according to the formula P·t=F_ni/F_p⋅C_F⋅k mode operation of the reactor and converters thickness (S) for depending CD (S), evaluation of uneven object loading parameters in the test volume of dependencies F (L, d) and D (L, d), as well as on movement of object relative to radiation source first in one side for time t₁ at power of reactor P, and after its rotation by 180° (on vertical or azimuth angle) – in reverse direction during time t₂=t₁ to initial position, where C_D=D_ni/D_p⋅P⋅t⋅k; C_F is a coefficient determined from the dependence of C_F(S); t=t₁+t₂ is duration of reactor operation at power; F_p and D_p – respectively values fluence neutron and gamma radiation in the reference point at a standard thickness of converters, defined by the calculated dependencies F_p (L, d), D_p (L, d) and normalized to one neutron from the reactor; k is proportionality coefficient, n/J; L and d are length and width of object (test volume).

EFFECT: possibility of radiation testing of objects with large dimensions.

1 cl, 8 dwg

Description

The invention relates to the field of testing of large-sized objects for radiation resistance in the radiation fields of research reactors. The objects of testing are samples of military and civilian equipment designed to perform work in radiation fields with high dose loads, for example, in accidents at nuclear hazardous facilities or nuclear explosions. Testing norms (NI) are the levels of exposure to radiation (loading parameters of an object), which are implemented on modeling installations during testing, taking into account the actual conditions of exposure to radiation on an object, in particular: in one time interval, with equal dose loads on the object and with unevenness loading parameters not more than 30% (requirements of regulatory documents). In evaluating the complex action of neutrons and gamma radiation for irradiation tests irreversible rules are neutron fluence (F _audio) with energies greater than 0.1 MeV, and the exposure dose of gamma-radiation (D _audio).

Under normal operating conditions of reactors, these requirements are not always feasible, since the dose of gamma rays during the reproduction of Φ _is , as a rule, several times smaller than the required value, and the uneven distribution of the loading parameters of the object in the irradiation zone exceeds the permissible norm. The increase in the missing dose of gamma rays in the test volume is carried out mainly due to devices that convert neutrons to gamma rays [1-4].

To form a homogeneous radiation field with acceptable non-uniformity of the object loading parameters, a method [5] was developed based on unilateral irradiation of the object and moving the platform with the reactor relative to the test object indoors. The reproduction of D _neither (simultaneously with F _nor ) is carried out by choosing the number of converters, their thickness and the layout of the reactor core (AZ). The disadvantage of this method is that when the reactor moves at power, there are always risk factors associated with either a change in the reactivity of the reactor reactor AZ due to the presence of various neutron reflectors in the form of walls close to the reactor or auxiliary equipment along the platform path, which affects for energy release in the reactor AZ. In addition, the width of the irradiation zone with permissible uneven parameters during unilateral irradiation of the object is small and is not more than 45 cm [6], and the dimensions of the test object are limited by the size of the room and in the conditions of irradiation at the PRIZ-M reactor do not exceed 5 m, which also limits the possibilities testing many dimensional objects.

The technology for increasing the size of the test volume with the permissible irregularity of the radiation parameters was proposed in the prototype method [7] of the claimed invention and is based on the superposition of the radiation fields from the reactor and neutron converters, determining the calculated dependences of the neutron fluence and the exposure dose of gamma radiation on the distance along the normal passing through the center of the AZ to the longitudinal axis of the irradiation zone, and coefficients characterizing the uneven distribution of the radiation parameters over the width of the zone, and also due to the choice of the reactor operating mode and the thickness of the converters during sequential irradiation of the object from two opposite sides in its stationary location (without moving) relative to the radiation source. Moreover, the permissible non-uniformity of the parameters of the acting radiation along the length of the irradiation zone (test volume) is realized only at small distances and depends on the width (d) of the zone. For example, at d = 50 cm, the length of the zone (L _d ) with an allowable non-uniformity of parameters does not exceed 1.5 m, and at d = 100 cm the value L _d = 80 cm, which is insufficient for testing objects with large dimensions.

The technical result of the claimed invention consists in reproducing test standards in a test volume with dimensions exceeding the dimensions of the area of two-sided irradiation of the object near the radiation source.

The technical result is achieved: by superposition of the radiation fields from the reactor and neutron converters to gamma-quanta, by determining the neutron fluence (Φ) with energies of more than 0.1 MeV and the exposure dose (D) of gamma-quanta in the zone of two-sided irradiation of the object, by choosing the operating mode of the reactor according to P⋅t = formula F _audio I / F _{p F} ⋅S ⋅k and thickness (S) converters, depending on C _D (S), evaluation of uneven loading of object parameters in dependence on the test volume F (L, d) and D (L, d), as well as as a result of the movement of the object relative to the radiation source first in one direction during the time t _1, and after turning it through 180 ° (from the vertical or azimuth angle) - in the opposite direction during the time t ₂ = t ₁ to the starting position, where t ₁ + t ₂ = t; C _D = D _neither / D _p ⋅P⋅t⋅k; t is the duration of the reactor at power P; С _Ф - coefficient determined by the dependence С _Ф (S); Ф _р and D _p - neutron fluence and gamma radiation dose at the reference point at standard thickness of converters, determined by the calculated dependences Ф _p (L, d), D _p (L, d) and normalized to one neutron from the reactor; L and d are the length and width of the test volume (object); k is the coefficient of proportionality, n / J; F _neither and D _nor - test standards set for their reproduction in the test volume.

As a parameter characterizing the non-uniformity of the parameters Ф and D, the value

where A is the value of the measured quantity.

The “reference (control) point" is selected at the boundary of the test volume with the maximum values of the parameters Ф and D after irradiating the object from two opposite sides and taking into account the standard thickness of the converters (7.7 cm).

The loading parameters of the object in the inventive method are the integral values of the levels of radiation affecting the object in the test volume when moving the object relative to the radiation source in two mutually opposite directions. The dimensions of the test volume are limited not only by the ability to reproduce the given parameters of the acting radiation (Ф _neither and D _nor ), but also by the possibilities of ensuring an allowable non-uniformity (≤30%) of the parameters in this volume. The loading parameters are calculated in the test volume without taking into account the attenuation of radiation in the object, i.e. by analogy with the calculation model for determining the parameters given in the regulatory documents for the actual conditions of equipment exposure.

Testing of the method was carried out at the reactor PRIZ-M. Computational studies were carried out using the Monte Carlo method, implemented in the MCNP program taking into account the real geometry of the placement of the reactor, converters and the test object. The research results are shown in FIG. 2-8.

In FIG. Figure 1 shows the layout of the reactor AZ (1) with converters (2) in the gateway range of the hull (3) and the test object on the site outside the hull, used for "step-by-step" movement of the object relative to the source. When implementing such a variant of moving an object, it is mentally divided into n equal parts (steps), then the length (a) of each part (or step) is L / n, and the length (r) of moving the object is L (n-1) / n, where L is the length of the test volume (test object). L _d - the length of the test volume (object) with an allowable unevenness of the radiation parameters. The object in the initial position (4) is placed so that the 1st section is opposite the AZ, symmetrical to the R axis, where the highest levels of the acting radiation are realized. After irradiation for a time t ₁ / n, the object moves one step along the X direction, then it is again irradiated for the same time. Operations with irradiation and moving the object are repeated until the last section of the AZ is irradiated. In this case, the total irradiation time of each section when moving in one direction is t ₁ . R is the coordinate from the center of the core along the width of the object (test volume), X is the coordinate along the direction of movement of the object from its original position to position (5) and vice versa.

In FIG. Figure 2 shows the predicted distribution of neutron fluence Φ (L, d) along an object with a length of L = 10 m and a width of d = 50 cm (a) and at d = 125 cm (b) at the boundary of the test volume (R = 1 m, graphs 1, 3) and along the central axis on R + d / 2 (2, 4) with the stationary location of the object (1, 2) near the source, as well as after two-way movement (3, 4). The values are normalized to one neutron from the reactor AZ. Dependencies (1, 2) are typical for the prototype method, dependencies (3, 4) are for the proposed method.

In FIG. 3 shows dose distributions of gamma rays D (L, d) along an object with the same notation as in FIG. 2.

In FIG. Figure 4 shows the dependences of the parameter j _D (L, d) characterizing the nonuniform distribution of the gamma radiation dose along the test volume with a length of L = 7 m, a width of d = 50 cm (1) and at d = 125 cm (2), as well as at L = 10 m, d = 50 cm (3) and at d = 125 cm (4), at L = 12 m, d = 50 cm (5) and at d = 125 cm (6). The parameter j was calculated by the formula (1).

In FIG. Figure 5 shows the dependences of the parameter j _Ф (L, d) for the neutron fluence along the test volume of length L = 7 m, width d = 50 cm (1) and at d = 125 cm (2), as well as at L = 10 m, d = 50 cm (3) and at d = 125 cm (4), at L = 12 m, d = 50 cm (5) and at d = 125 cm (6).

In FIG. Figure 6 shows the dependences of the neutron fluence Ф _р (L, d) at the reference point for test volumes from 7 m to 12 m long with values d = 50 cm (1), d = 80 cm (2) and d = 125 cm (3) .

In FIG. Figure 7 shows the dependences of the doses of gamma radiation D _p (L, d) at the reference point for test volumes from 7 m to 12 m long with values d = 50 cm (1), d = 80 cm (2) and d = 125 cm ( 3).

In FIG. Figure 8 shows the distribution of the exposure dose of gamma radiation C _D (S) = D (S) / D _p and neutron fluence C _Ф (S) = Ф (S) / Ф _p [8]. The values of F _p and D _p calculated for the standard thickness (S _article ) converters 7.7 cm

From the above data it follows that when moving an object relative to the reactor core, the distance along the length of the test volume (object) with an allowable non-uniformity of the parameters of the acting radiation is several times greater (at L = 10 m and d = 50 cm more than 6 times) than with a stationary arrangement object near a radiation source. With increasing d, the non-uniformity of parameters along the length of the object increases, with increasing L it decreases. The unevenness of the parameters for objects with L = 10 and 12 m is less than for objects with L = 7 m. At d = 50 cm, the permissible unevenness of these parameters is equalized almost over the entire length of the object. The maximum values of the parameters of the acting radiation (values of F _p and D _p ) are formed in the middle part of the test volume (object) at the boundary facing the source, since this part of the object is located closer to the reactor core, i.e. in the most intense range of radiation exposure, compared with areas remote from the middle. The values ( _{f p} , D _p ) shown in FIG. 6 and 7, are used in the calculation formulas when determining the time of irradiation of the object and the thickness of the converters.

Algorithm playback setpoints NO _(nor F = 10 ^{to 13} N / cm _2, and _audio D = 1,2⋅10 ⁴ P) onto PRIZE M-reactor can be seen in the test object c L = 7, m and d = 50 cm.

1. By dependencies 1 in FIG. 6 and FIG. 7, the values of Ф _р = 3.18⋅10 ^-6 n / cm ² and D _p = 3.24⋅10 ^-15 Р are determined at the reference point at R = 1 m and S = 7.7 cm, and the value C is also estimated _Φ = 1 according to C _Φ (S) in FIG. 8.

2. predicted energy release (Q) in the PP with the formula Q = P⋅t = F _audio I / F _p = _F ⋅K⋅S October ¹³ / 3,18⋅10 ^-6 ⋅4⋅ ¹⁰ ⋅1 = 7,86⋅ 10 ⁷ J, where t = t ₁ + t ₂ , K = 4⋅ ¹⁰ n / J.

3. The mode of operation of the reactor is selected (the duration of irradiation at a given power). At P = 2 kW, the duration of the object irradiation is t = Q / P = 7.86⋅10 ⁷ / 2⋅10 ³ = 3.93⋅10 ⁴ s (10.92 hours).

4. The value of C _{D is} determined by the formula C _D = D _neither / D _p ⋅ Q⋅К = 1.2⋅10 ⁴ / 3.24⋅10 ^-15 ⋅7.86⋅10 ⁷ ⋅4⋅10 ¹⁰ = 1, 18. According to C _D (S) in FIG. 8, the thickness of each of the two converters (S = 13 cm) is determined, which allows reproducing the dose of gamma radiation to the desired value. Then, the value of the coefficient С _Ф is determined by the dependence С _Ф (S).

5. The permissible non-uniformity of the loading parameters along the length of the test volume is evaluated. Values j _D ≤30% are provided over the entire length (graph 1 in Fig. 4). Values j _Ф ≤30% - along the length of 6.1 m (graph 2 in Fig. 5), which is more than 4 times the size of the zone with the permissible unevenness of the loading parameters of the object of the prototype method.

6. The movement of the object relative to the radiation source is carried out according to the scheme in FIG. 1, where a = 1.4 m, r = 5.6 m.

The technical result of the invention is the reproduction of test standards in a test volume with dimensions exceeding the dimensions of the area of two-sided irradiation of the object near the radiation source, which allows testing objects with large dimensions.

Sources of information

1. Kuvshinov M.I., Koshelev A.S., Smirnov I.G. et al. Transformation of fast neutron radiation from pulse reactors BIR-2M, BR-1, BIGR using n-γ converters // Issues of Atomic Science and Technology. Series: Physics of Nuclear Reactors, vol. 2 - Lytkarino, 1992, p. 3.

2. Vasiliev A.V., Nenadyshin N.N., Romanenko A.A. The gamma-neutron field converter of the Bars-4 pulsed nuclear reactor // Scientific and Technical Collection “Radiation Stability of Electronic Systems - Stability-2007”, issue 10 - M., MEPhI, 2007, p. 169.

3. Gritsay V.N., Tulikov F.F., Kazantsev V.V., Pikalov G.L., Solodovnikov N.I. A device for forming a field of radiation loading of objects when they are tested for radiation resistance. RF patent for the invention No. 2284068 of March 24, 2005

4. Pikalov G.L., Krasnokutsky I.S., Koynov D.V., Artamonov D.N. A method for simultaneously reproducing set values of a neutron fluence and an exposure dose of gamma radiation in research reactors. RF patent for the invention No. 2641890 dated 05/10/2016.

5. Pikalov G.L., Bazaka Yu.G., Krasnokutsky I.S., Komarov N.A., Rymar A.I. A method for simultaneously reproducing set values of neutron fluence and exposure dose of gamma radiation in a research reactor. RF patent for the invention No. 2497214 from 10.27.2013

6. Komarov N.A., Kostyaev S.V., Nekhay E.N., Pikalov G.L., Chaplygin A.A. Radiation parameters and thermodynamic characteristics of the modernized PRIZ-M reactor // Scientific and Technical Collection "Radiation Stability of Electronic Systems - Stability-2009", vol. 12 - M., MEPhI, 2009, p. 189.

7. Pikalov G.L., Burlaka I.A., Nikolaev O.A., Krasnokutsky I.S., Korablev M.Yu. A method for simultaneously reproducing set values of a neutron fluence and an exposure dose of gamma radiation in research reactors. RF patent for the invention No. 2686838 of 05/21/2018

8. Pikalov G.L., Burlaka I.A., Nikolaev O.A., Krasnokutsky I.S., Korablev M.Yu. Reproduction of test standards at the PRIZ-M reactor with two-sided irradiation of an object // Questions of atomic science and technology. Series: Physics of Radiation Exposure to Radio-Electronic Equipment, vol. 3 - Lytkarino, 2018, p. 55.

Claims (1)

A method for reproducing test standards for large-sized objects in research reactors, based on the superposition of radiation fields from the reactor and neutron to gamma-ray converters, determination of neutron fluence (Ф) with energies above 0.1 MeV and exposure dose (D) of gamma-quanta (loading parameters object) in the double exposure object area selection mode according to the formula of the reactor _audio P⋅t = F / F _{p F} ⋅S ⋅k and thickness (S) converters, depending on C _D (S), where C _D = _{D audio} / D _p ⋅P⋅t⋅k; t is the duration of the reactor at power P; С _Ф - coefficient determined by the dependence С _Ф (S); F _p and D _p - respectively, the neutron fluence and the dose of gamma radiation at the reference point at a standard thickness of the converters, normalized to one neutron from the reactor; k is the coefficient of proportionality, n / J; Ф _neither and D _nor - test norms set for their reproduction in a test volume, characterized in that the dependences Ф (L, d) and D (L, d), Ф _p (L, d) and D _p (L, d), which determine the non-uniformity of the loading parameters of the object in the test volume, as well as the values of F _p and D _p , then the test object is moved relative to the radiation source, first one way for a time t ₁ , and after its rotation through 180 ° (vertical or azimuthal angle) - in the opposite direction during the time t ₂ = t ₁ to the starting position, where t = t ₁ + t _2, L and d - length and width of sites a (the test volume).

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