CN104157316A - Evaluation method for maintenance opportunity of nuclear reactor containment internal coating layer - Google Patents

Abstract

The invention relates to an evaluation method for a maintenance opportunity of a nuclear reactor containment internal coating layer. The evaluation method successively comprises the following steps: (a) determining the area S of a nuclear reactor containment break affected zone, and calculating the mass M[1] of latent coating layer fragments; (b) carrying out visual inspection on four coating layer systems of a nuclear reactor containment outside the break affected zone; (c) followed by testing tested points, and recording test results; (d) determining LOCA simulation test unqualified ratios of the four coating layer systems; (e) combining with a formula 2, respectively calculating the total mass M[2] of the latent fragments outside the break affected zone; (f) determining the mass M[3] of a qualified coating layer falling off during a reactor machine set normal operation; (g) determining X[CCD] and the maximum value M[max] of all the coating layer fragments produced from loss of coolant accidents; and (h) according to a formula (3), calculating the approximation rate gamma. The evaluated total amount of the coating layer fragments is quantized and is compared with the amount of critical coating layer fragments, so as to confirm whether a nuclear reaction is required to be stopped for maintenance of the coating layer in the containment.

Description

A method for evaluating the maintenance timing of coatings in the containment of nuclear reactors

technical field

The present invention relates to a method for evaluating the maintenance timing of nuclear reactors, in particular to a method for evaluating the maintenance timing of the inner coating of the nuclear reactor containment vessel.

Background technique

A nuclear reactor, also known as an atomic reactor or a reactor, is a device that can maintain a controllable self-sustaining chain nuclear fission reaction and is equipped with nuclear fuel to achieve a large-scale controllable fission chain reaction. Reactor containment (also known as reactor protective shell) is a closed container that prevents radioactive materials from escaping when the nuclear reactor is in operation or in an accident. When an accident occurs in a nuclear power plant reactor, a large amount of radioactive substances will be released. As the last nuclear safety barrier, the containment can prevent the spread of radioactive substances and pollute the surrounding environment; at the same time, it is also often used as the enclosure structure of the reactor building to protect the reactor equipment system from the adverse effects of the outside world. , it is a huge special container structure.

The reactor containment is coated with special coatings for nuclear power plants, which must meet requirements such as chemical composition, fire resistance, salt spray test, radiation resistance, chemical corrosion resistance, and simulated DBA qualification. Due to the large coating area, complex irradiation environment, and few movable windows, the inner coating of the reactor containment basically does not meet the conditions for large-scale maintenance. The continuous increase of coating fragments increases the risk of recirculation pit blockage failure, which brings risks to the safe operation of the reactor; however, it is impossible to easily stop the nuclear reaction during the operation of the reactor and carry out the maintenance of the coating inside the containment vessel. Otherwise, a lot of material and financial resources will be wasted, so a scientific method is needed to determine the timing of the coating repair in the containment vessel.

Contents of the invention

The purpose of the present invention is to provide a method for evaluating the maintenance opportunity of the inner coating of the nuclear reactor containment vessel in order to overcome the deficiencies of the prior art.

In order to achieve the above object, the technical solution adopted in the present invention is: a method for evaluating the timing of coating maintenance in the containment of a nuclear reactor, which is characterized in that it includes the following steps in sequence:

(a) Measure the area S of the zone affected by the breach of the containment vessel of the nuclear reactor, and combine the known thickness H and density ρ of the four coating systems to calculate the mass M ₁ of latent coating fragments in the zone affected by the breach according to formula (1);

M ₁ =ρ×S×H(1);

(b) Visually inspect the four coating systems PIC100I, PIC151I, PIC152I and PIC155I of the nuclear reactor containment outside the breach-affected area, and then compare the inspection results with the standard coating to determine the difference between the four coating systems. Qualified ratios are recorded as P _v0 , P _v1 , P _v2 , and P _v5 respectively;

(c) On the above-mentioned four kinds of coating systems outside the impact area of the breach, select multiple test areas for the coatings that pass the visual inspection, select at least six test points for each test area, and then test the test points Carry out grinding, chip removal, stick test column with glue, described test column is connected with tester and carry out tensile force test, record test result, determine the unqualified ratio of adhesion force of described four kinds of coating systems, correspond to record respectively P _A0 , P _A1 , P _A2 , P _A5 ;

(d) Add boric acid and NaOH to deionized water to prepare an alkaline buffer solution, and the alkaline buffer solution is set at a flow rate of 1×10 ^-4 ~1×10 ^-3 m ³ /m ² ·s at 120~180 Spray into the container with samples of the four coating systems outside the impact area of the breach at ℃, spray continuously for 24 to 50 hours and then place in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for at least 2 weeks, determine the unqualified ratio of the LOCA simulation test of the four kinds of coating systems, correspondingly recorded as P _L0 , P _L1 , P _L2 , P _L5 ;

(e) According to the quality of the four known coating systems PIC100I, PIC151I, PIC152I and PIC155I, which are respectively denoted as M _PIC100I , M _PIC151I , M _PIC152I and M _PIC155I , combined with formula 2 and formula 3 to calculate the outside of the crack influence area The total mass of latent debris M ₂ ;

M ₂ =M _PIC100I ×{[P _V0 + P _A0 (1-P _V0 )] +P _L0 [1-P _V0 - P _A0 (1-P _V0 )]}+ M _PIC151I ×{[P _V1 + P _A1 (1-P _V1 )] +P _L1 [1-P _V1 - P _A1 (1-P _V1 )]}+ M _PIC152I ×{[P _V2 + P _A2 (1-P _V2 )] +P _L2 [1- P _V2 - P _A2 (1-P _V2 )]} + M _PIC155I {[P _V5 + P _A5 (1-P _V5 )] + P _L5 [1-P _V5 - P _A5 (1-P _V5 )]} ( 2);

(f) Carry out a visual inspection of the containment pit of the nuclear reactor to determine the qualified coating quality M ₃ that falls off during the normal operation of the reactor unit;

(g) Check the model of the nuclear reactor unit, determine the critical amount of coating debris X _CCD of the reactor and the maximum value M _max of all coating debris generated under the loss of water accident;

(h) Calculate the approach rate γ according to the formula (3). When the approach rate γ is less than 100%, the nuclear reactor can carry out routine maintenance work; when the approach rate γ is greater than 100%, stop the nuclear reaction and carry out maintenance of the coating inside the containment ;

(3).

Preferably, said aging detection includes loss of gloss, cracking, flaking, blistering, chalking, discoloration, rust spots and mold growth properties of the coating.

Optimally, in step (c), the coating to be tested should be fully dried and cured, and the test points should avoid coating defects.

Optimally, in step (c), the speed of the applied force does not exceed 1 MPa/s, and the stretching is completed within 90s.

Due to the application of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art: the method for evaluating the timing of coating maintenance in the nuclear reactor containment vessel of the present invention quantifies the total amount of coating fragments evaluated into latent coatings in the area affected by the breach. Layer debris mass M ₁ , the total mass of latent debris outside the breach-affected area M ₂ , the shedding qualified coating mass M ₃ , and the maximum value of all coating debris M _max generated under dehydration accidents, so as to compare it with the critical coating The amount of debris is compared to confirm whether it is necessary to stop the nuclear reaction for inspection of the inner coating of the containment vessel.

Detailed ways

Preferred embodiments of the present invention will be described in detail below.

Example 1

The method for evaluating the maintenance timing of the inner coating of the nuclear reactor containment of the present invention comprises the following steps in sequence:

Firstly, the area S of the breach-affected area of the reactor building is measured, and the mass M ₁ of latent coating fragments in the breach-affected area is calculated according to the formula (1) in combination with the thickness H and density ρ of the four known coating systems;

M ₁ =ρ×S×H(1);

Followed by visual inspection: visual inspection of the four coating systems PIC100I, PIC151I, PIC152I and PIC155I of the reactor building outside the breach affected area, and then comparing the inspection results with standard coatings to determine the four coating systems The unqualified ratios are correspondingly recorded as P _v0 , P _v1 , P _v2 , and P _v5 . The specific visual inspection includes: supplemented by tools such as a flashlight and a magnifying glass, inspect the steel lining surface in the reactor building and the condition of the civil steel structure, wall, floor, and ceiling surface coatings (four coating systems) in each room, Focus on inspecting the phenomenon of loss of gloss, cracking, peeling, blistering, powdering, discoloration, rust, mildew, etc. of the coating; inspection methods include general general inspection and key inspection for defect areas; in order to improve inspection efficiency, Formulate the basic inspection route and content for the reference of the inspectors, and the specific route and content shall be determined by the inspectors depending on the site conditions.

Then there is the adhesion test: on the above four coating systems outside the impact area of the breach, select multiple test areas for the coatings that pass the visual inspection, and select at least six test points for each test area, and then test all the coating systems. The above test points are polished, deswarfed, glued to the test post, the test post is connected to the tester to perform a tensile test, the test results are recorded, and the unqualified ratio of the adhesion of the four coating systems is determined. Correspondingly denoted as P _A0 , P _A1 , P _A2 , and P _A5 . The test points are selected from the area where the substrate is flat and firm, and the area and surrounding space can be used to place test instruments, and representative areas and test points of different coating systems should be selected; the coating to be tested should be fully dry and cured, flat, clean, and the surface The state is consistent with the surrounding area, avoiding coating defects. If there are test points with unqualified adhesion, more test points should be added to check the range of unqualified coatings. The tensile force test is as follows: before bonding the test column, take pictures of the selected test points and mark the positions on the record sheet; for the selected test points, lightly polish them with spun paper, and then remove them with a brush. Degrease the test column with absolute ethanol, and then let it dry; according to the instructions of the adhesive, mix the adhesive in proportion for use (for ordinary/quick-drying epoxy adhesive Use within 1 hour); apply the adhesive to the surface of the test column, use as little glue as possible; press the test column on the coated surface, and move the test column appropriately to remove air; try to remove excess glue; The test column is fixed on the surface of the coating; the curing time of the glue is greater than 24 hours (the curing time of the quick-drying adhesive is greater than 2 hours); the tape is removed; the coating is cut along the periphery of the test column with a ring knife or wallpaper knife ( This step is only required when the pulling force inside the coating is greater than the adhesion of the coating); the tester is returned to zero; connect the tester to the test column, apply a little force, and check whether the instrument is straight; apply the pull evenly and slowly Stretch until the test column is pulled apart, the acceleration speed should not exceed 1MPa/s, and complete the stretching within 90s; if the test column is not pulled apart after reaching the full range of the instrument, the experiment will end, and the instrument will be unloaded and removed Finally, knock down the test column with a wooden stick. After drawing, put the test column into the corresponding numbered sample bag, record the data on the drawing site and take pictures. After the bonding, drawing and recording work is completed, the damaged coating on site is repaired immediately.

Then carry out the LOCA simulation test: add boric acid and NaOH to deionized water to prepare an alkaline buffer solution (equivalent to boric acid containing 2.5g/L boron, pH of the spray solution = 9.3), and the alkaline buffer solution is diluted with 1× Spray the flow rate of 10 ^-4 ~1×10 ^-3 m ³ /m ² s at 120~180°C into the container with samples of the four coating systems outside the area affected by the breach, and spray continuously for 24~50 After one hour, place it in an environment with a temperature of 23±2°C and a relative humidity of 50±5% for at least 2 weeks, determine the unqualified ratio of the LOCA simulation test of the four coating systems, and record them as P _L0 and P _L1 respectively , P _L2 , P _L5 ;

According to the mass of the four known coating systems PIC100I, PIC151I, PIC152I and PIC155I, which are denoted as M _PIC100I , M _PIC151I , M _PIC152I and M _PIC155I , respectively, the total mass M of latent debris outside the impact area of the breach is calculated in combination with formula 2 ₂ ;

M ₂ =M _PIC100I ×{[P _V0 + P _A0 (1-P _V0 )] +P _L0 [1-P _V0 - P _A0 (1-P _V0 )]}+ M _PIC151I ×{[P _V1 + P _A1 (1-P _V1 )] +P _L1 [1-P _V1 - P _A1 (1-P _V1 )]}+ M _PIC152I ×{[P _V2 + P _A2 (1-P _V2 )] +P _L2 [1- P _V2 - P _A2 (1-P _V2 )]} + M _PIC155I {[P _V5 + P _A5 (1-P _V5 )] + P _L5 [1-P _V5 - P _A5 (1-P _V5 )]} ( 2).

Then carry out visual inspection on the containment pit of the nuclear reactor to determine the qualified coating quality M ₃ that falls off during the normal operation of the reactor unit; check the technical parameters and models of the nuclear reactor unit, pit filter, safety injection pump and safety injection pump, Determine the reactor critical coating debris amount X _CCD (The specific value of X _CCD may be different with the design technical parameters of pit filter, safety injection pump and safety injection pump; but once the nuclear reactor unit is built, X _CCD is a fixed value. ) and the maximum value M _max of all coating fragments generated under loss of water accidents.

Finally, the approach rate γ (the ratio of the estimated amount of total coating fragments to the critical amount of coating fragments) is calculated according to formula (3), where the estimated and calculated amount of coating fragments X _ACD is the latent coating in the area affected by the breach The sum of the fragment mass M ₁ , the total mass of latent fragments M ₂ outside the breach-affected area, the qualified coating mass M that falls off during the normal operation of the reactor unit, and the maximum value M _max of all coating fragments generated under the loss of water accident, when When the approach rate γ is less than 100%, it is enough to carry out routine maintenance work on the nuclear reactor; when the approach rate γ is greater than 100%, the nuclear reaction should be stopped and the maintenance of the inner coating of the containment vessel should be carried out;

(3).

In addition, when there are irregularities involving nuclear reactor units, pit filters, safety injection pumps, safety injection pumps, and coating types in the record documents of the construction of nuclear power plants, the variables caused by such irregularities should be used as coating fragments The mass is quantified and included in the amount of coating fragments X _ACD , which makes the evaluation of the timing of stopping the nuclear reaction and repairing the coating inside the containment more accurate.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (4)

1. nuclear reactor safety shell internal coating is keeped in repair the appraisal procedure on opportunity, it is characterized in that, comprises the following steps successively:

(a) measure nuclear reactor safety shell cut zone of influence area S, and in conjunction with known four kinds of coat system thickness H and density p, according to formula (1), calculate the cut zone of influence coating fragment mass M of hiding ₁;

M ₁=ρ×S×H（1）；

(b) four kinds of coat system PIC100I, PIC151I, PIC152I and PIC155I of cut zone of influence outer core containment vessel are carried out to visual examination, subsequently check result and standard coated are contrasted to the defective ratio of determining described four kinds of coat systems, correspondence is designated as P respectively _v0, P _v1, P _v2, P _v5;

(c) outside the cut zone of influence on described four kinds of coat systems, the coating that visual examination is qualified is respectively selected to a plurality of test zones, each test zone is chosen at least six test points, then described test point is polished, debris removal, with glue, is stained with examination post, described examination post is connected with tester and carries out tensile force test, logging test results, determines the defective ratio of adhesion of described four kinds of coat systems, and correspondence is designated as P respectively _a0, P _a1, P _a2, P _a5;

(d) in deionized water, add boric acid and NaOH to be mixed with alkaline buffer, by described alkaline buffer with 1 * 10 ^-4~ 1 * 10 ^-3m ³/ m ²the flow of s sprays in the container that four kinds of coat system samples outside the cut zone of influence are housed at 120 ~ 180 ℃, continuously within 24 ~ 50 hours, to be placed on temperature be at least 2 weeks in 23 ± 2 ℃, the relative humidity environment that is 50 ± 5% to spray, the defective ratio of LOCA simulation test of determining described four kinds of coat systems, correspondence is designated as P respectively _l0, P _l1, P _l2, P _l5;

(e) according to the quality of known four kinds of coat system PIC100I, PIC151I, PIC152I and PIC155I, be designated as respectively M _pIC100I, M _pIC151I, M _pIC152Iand M _pIC155I, in conjunction with formula (2), calculate respectively the gross mass M of the fragment of hiding outside the cut zone of influence ₂;

M ₂=M _PIC100I×{[P _V0+?P _A0（1-P _V0）]?+P _L0[1-P _V0-?P _A0（1-P _V0）]}+?M _PIC151I×{[P _V1+?P _A1（1-P _V1）]?+P _L1[1-P _V1-?P _A1（1-P _V1）]}+?M _PIC152I×{[P _V2+?P _A2（1-P _V2）]?+P _L2[1-P _V2-?P _A2（1-P _V2）]}+?M _PIC155I{[P _V5+?P _A5（1-P _V5）]?+P _L5[1-P _V5-?P _A5（1-P _V5）]}（2）；

(f) nuclear reactor safety shell melt pit is carried out to visual examination, determine the qualified coating quality M coming off in reactor unit normal course of operation ₃;

(g) check nuclear reactor unit model, determine the critical coating amount of debris of reactor X _cCDwith the whole coating fragment maximal value M that generate under loss of-coolant accident (LOCA) _max;

(h) according to formula (3), calculate and approach rate γ, when the rate γ of approaching is less than 100%, nuclear reactor carries out conventional maintenance job; When the rate γ of approaching is greater than 100%, stops nuclear reaction and carry out the internally coated maintenance of containment;

（3）。

2. the appraisal procedure of the coating amount of debris of hiding in reactor building under loss of-coolant accident (LOCA) according to claim 1, is characterized in that: described aging detection comprise coating loss of gloss, ftracture, peel off, foaming, efflorescence, variable color, rust spot and mildew character.

3. the appraisal procedure of the coating amount of debris of hiding in reactor building under loss of-coolant accident (LOCA) according to claim 1, is characterized in that: in step (c), described coating to be tested is dry solidification fully, and test point is avoided holiday.

4. the appraisal procedure of the coating amount of debris of hiding in reactor building under loss of-coolant accident (LOCA) according to claim 1, is characterized in that: in step (c), described afterburning speed is no more than 1MPa/s, and completes stretching in 90s.