JP2006119020A - Evaluation method for element deposition on surface of fuel clad and program for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate element deposition on the fuel clad surface of a nuclear power plant in operation. <P>SOLUTION: Among the off gas nuclide of an operating nuclear power plant, radioactivity intensity ratio of nuclides Xe-135m, Xe-135, Xe-138 and Kr-88 or nuclides Xe-135m, Xe-135, Xe-138 and Kr-87 is determined by measurement and from the radioactivity ratio, component ratio of them is obtained. From the component ratio, in-core migration time of the off-gas and iodine is evaluated and existence of deposition of fissile nuclides is judged from the in-core migration time of the off-gas and iodine. In another method, radioactivity intensity ratio of nuclides I-132, I-134 and I-135 among iodine isotopes in core water of an operating nuclear power plant is obtained by measurement, and from the radioactivity intensity ratio, the component ratio of the nuclides is obtained. From the component ratio, core water purification system coefficient of Te in the operating nuclear power plant is calculated. From the core water purification system coefficient of Te, fluctuation of deposition of fissile nuclide on the fuel rod outer surface is judged. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for evaluating element deposition on the surface of a fuel cladding tube based on radiation data measured in the routine of an operating nuclear power plant and a program therefor.

  In plants where there is no damage to the fuel cladding, uranium, an impurity contained in the cladding, is the main source, and seven nuclides of Kr and Xe are detected in the offgas, and five iodine isotopes are detected in the reactor water. . The concentrations and isotopic compositions of these elements are almost constant in the absence of cladding failure during normal operation. When the cladding is broken, the isotope composition is changed by releasing the isotopes having a long half-life accumulated in the fuel rod as the concentration of these elements increases. Conventionally, the soundness of the fuel cladding tube is determined by detecting this variation. In addition, a method for evaluating the offgas release mechanism from the change in the isotope composition has been proposed. These methods are disclosed in Patent Document 1 and the like.

  In the description in Non-Patent Document 1 regarding the method for evaluating the origin of offgas, the main origin of offgas in a plant without experience of fuel failure is that the natural uranium contained in the zircaloy cladding tube is changed to Pu by combustion. The amount of uranium is estimated to be about 100 ppb on average in the core. On the other hand, fissionable nuclides released into the reactor water when the cladding tube breaks also adheres to the surface of the cladding tube and becomes the source of off-gas. Therefore, in order to evaluate the future transition of the off-gas level in the plant that experienced the cladding tube failure It is necessary to understand whether the current off-gas origin is impurities or adhesion. However, since the amount of impurity uranium in zircaloy is not necessarily the same for each zircaloy cladding tube, it is difficult to determine the amount of impurities and adhesion using the off-gas emission value (Bq / s), which is an absolute value. .

  To determine whether uranium components are attached to the surface of a fuel assembly loaded in a nuclear reactor, it is generally possible to collect the components attached to the surface of the fuel assembly and perform chemical analysis and radiation measurement. Although necessary, chemical separation and sample preparation necessary for collecting surface deposits and measuring α-rays are very complicated, so they were not actually performed, and it was difficult to evaluate the amount of deposits. .

In the method of evaluating off-gas origin from the production ratio of ¹³⁸ Xe / ⁸⁸ Kr described in Non-Patent Document 1 as a method for evaluating the presence or absence of fissile nuclide attachment on the surface of the cladding tube, ¹³⁸ Xe has a short half-life. For this reason, attenuation correction is required for each measurement data based on the transition time from generation to measurement in an off-gas system. This transition time evaluation method differs for each measurement data (batch) depending on the structure of each plant and the operating conditions such as output and off-gas flow rate even in the same plant. A method is used in which the radioactivity intensity ratio of the ^135m Xe / ^135g Xe isotope obtained on the γ-ray spectrum is used as an internal standard.

However, since ¹³⁵ Xe isomers (isobares) used for time decay correction are both generated by ¹³⁵ I decay and direct fission, ^135m Xe with a short half-life is strongly influenced by iodine behavior in the reactor water. On the other hand, it has been reported that changes in iodine behavior such as a decrease in the concentration of iodine in reactor water occur with the injection of hydrogen, zinc (Zn), and the like, which are carried out in many plants recently. In addition, the iodine concentration in the reactor water varies depending on the flow rate and removal performance of CUW (cleanup water). For this reason, it was difficult to evaluate the origin of offgas by calculating the offgas transition time of all plant data only from the isotope ratio of ^135m Xe / ^135g Xe.

  On the other hand, elements brought into the reactor water due to elution from the structural material are activated on the surface of the cladding tube, increasing the amount of exposure. For this reason, attempts have been made to reduce the exposure dose by changing the reactor water environment to control the deposition rate on the surface of the cladding tube. In recent plants, the amount of radioactive corrosion products is suppressed by injection of hydrogen and precious metals to reduce exposure. In the plant in which these injections are performed, the reactor water state changes, and the behavior of various fission products changes in addition to the iodine that is usually measured simultaneously with the corrosion products.

The rare gas components krypton (Kr) and xenon (Xe) measured in the operating plant, and iodine (I) in the reactor water differ greatly in chemical properties from radioactive corrosion products such as ⁶⁰ Co and ⁵⁴ Mn. The uranium adhering to the cladding surface behaves like a corrosion product and adheres to the outer surface of the fuel cladding for a long time. On the other hand, tellurium (Te), which is a precursor of iodine, exhibits an intermediate property between non-metallic and metallic properties. For this reason, grasping the behavior change of Te is a good index for grasping the reactor water environmental conditions in the operation plant.

However, the activity intensity of fission products is lower than that of corrosion products in many plants, and Te has chemical properties located between iodine and corrosion products, so evaluate Te behavior. It was difficult. In addition, since it is necessary to collect a sample from the surface of the fuel body after stopping, it is difficult to measure the adhesion ratio on the surface of the fuel cladding tube with a nuclide having a short half-life.
JP 60-178392 A An Estimation Method for Off-gas Sources in a Boiling Water Reactor with Nondefective Fuel, M. TAKAHASHI, Nucl. Technol. Vol. 135, 230 (2001), American Nuclear Society

  When the fuel cladding tube breaks, the off-gas components with a long half-life accumulated inside are released, and the radioactivity intensity of the seven off-gas nuclides shows almost the same value. Is evaluated. When the cladding tube is not damaged, off-gas nuclides mainly originate from uranium impurities in the cladding tube, but some of the fuel components released into the reactor water when the cladding tube breaks adhere to the outer surface of the cladding tube. Will also be the source of new off-gas and fission products such as iodine, resulting in increased radiation dose rates associated with plant operation.

  The adhering fuel component adheres to the surface of the cladding tube for a long period of time, and gradually discharges into the coolant and reattaches while continuing to transmutate by irradiation. This release of fissionable nuclides (mainly α-emitters) and some fission products (FP) into the coolant also occurs during cooling storage for a certain period after irradiation of the fuel assembly, and the fuel storage pool This contributes to an increase in the radioactivity concentration and the dose rate in the atmosphere around the pool.

  In addition, when the fuel body is reprocessed, the radioactive concentration of the reprocessed storage pool is specified, so it is necessary to reduce the amount of adhesion as much as possible, but the fissionable nuclide adhering to the surface of the cladding tube is necessary. For the evaluation, sampling from the surface of the cladding tube and analytical measurement are required.

  However, since a special device is required for quantitative sample collection from the surface of the cladding tube and subsequent chemical separation measurement, it is extremely difficult during operation. It is important to establish

  The chemical state of the reactor water affects the amount of elements deposited on the surface of the fuel cladding. From the viewpoint of fuel assurance, dissolved oxygen, iodine and metal impurity concentrations, pH, conductivity, etc. are measured as changes in the reactor water chemical state. Here, in the actual element behavior evaluation, direct measurement of the target element is the most accurate in knowing the change. However, as described above, there is no known method for evaluating not only uranium (U) having a long half-life but also fission products having a short half-life.

  In addition, there are a wide variety of FP nuclides produced by impurities in the cladding and fissile nuclides attached to the surface. FP nuclides include nuclides such as Te that are sensitive to changes in the redox state of reactor water, but it is difficult to measure these nuclides simply and constantly.

  On the other hand, iron, copper, nickel, chromium, etc. are measured as corrosion products in the reactor water, and iodine of the FP component is also measured at the same time, but the redox of the elements in the reactor water that fluctuates due to hydrogen injection or noble metal injection. In the evaluation of the state of the fuel, it is important for the evaluation of fuel soundness to measure the concentration change of elements more sensitive to redox and the behavior change of various elements.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for evaluating the adhesion of elements on the surface of a fuel cladding of an operating nuclear power plant, and a program for realizing the method. And

  The present invention is for achieving the above object, and the first aspect is a method for evaluating element adhesion on the surface of a fuel cladding tube of an operating nuclear power plant, among the off-gas nuclides of the operating nuclear power plant. Xe-135m, Xe-135, Xe-138 and Kr-88 nuclide radioactivity intensity ratio, or Xe-135m, Xe-135, Xe-138 and Kr-87 nuclide radioactivity intensity ratio Obtain the composition ratio of the above nuclide based on this radioactivity intensity ratio, evaluate the transition time of the off-gas and iodine in the furnace based on this composition ratio, and determine the fissionable nuclide by the transition time of the off-gas and iodine in the furnace. It is characterized by determining the presence or absence of adhesion.

  The second aspect of the present invention is a method for evaluating element adhesion on the surface of a fuel cladding tube of an operating nuclear power plant. Among iodine isotopes in reactor water of an operating nuclear power plant, I-132, I- The radioactivity intensity ratio of 134 and I-135 nuclides was determined by measurement, the composition ratio of the above nuclides was determined based on this radioactivity intensity ratio, and based on this composition ratio, the Te reactor at the nuclear power plant in operation A water purification system coefficient is calculated, and based on the reactor water purification system coefficient of Te, variation in adhesion of fissile nuclides on the outer surface of the fuel rod is determined.

  Furthermore, a third aspect of the present invention is a program for causing a computer to evaluate element adhesion on the surface of a fuel cladding tube of an operating nuclear power plant, and among the off-gas nuclides of the operating nuclear power plant, Xe-135m Xe-135, Xe-138 and Kr-88 nuclide radioactivity intensity ratio, or Xe-135m, Xe-135, Xe-138 and Kr-87 nuclide radioactivity intensity ratio Based on the composition ratio of the nuclide based on this, the transition time of the off-gas and iodine in the furnace is evaluated, and the presence / absence of the attachment of the fissile nuclide is determined based on the transition time of the off-gas and iodine in the furnace. It is characterized by making a computer function.

  Furthermore, a fourth aspect of the present invention is a program for causing a computer to evaluate element adhesion on the surface of a fuel cladding tube of an operating nuclear power plant, among iodine isotopes in reactor water of the operating nuclear power plant, Based on the result of measurement of the radioactivity intensity ratio of the nuclides of I-132, I-134 and I-135, the composition ratio of the above nuclides was obtained, and based on this composition ratio, And a computer is made to function so as to determine the fluctuating variation of fissile nuclide attachment on the outer surface of the fuel rod based on the Te water purification system coefficient.

  According to the present invention, it is possible to easily evaluate the adhesion of elements on the surface of a fuel cladding tube of an operating nuclear power plant.

  Embodiments of an element adhesion evaluation method on the surface of a fuel cladding according to the present invention will be described below with reference to the drawings.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic system diagram for explaining the generation and migration behavior of Xe in a general boiling water reactor. The core 1 is disposed in the reactor pressure vessel 10, where the reactor water 2 boils and steam is generated. The steam that exits the reactor pressure vessel 10 passes through the steam system 3 to work in the steam turbine 8, condenses in the condenser 4, and becomes condensate. The condensate is returned to the reactor pressure vessel 10 through the condensate purification system 6.

  Fig. 1 shows off-gas (Kr, Xe) among the fission products produced in the core 1 and precursors involved in the production (mainly Te and I in the case of Xe and mainly Br in the case of Kr). An outline of the transition behavior from the reactor water 2 and the steam system 3 to the off-gas system 5 is shown. The off-gas system 5 is branched from the condenser 4. Since the reactor water and steam system in the reactor system forms a closed loop, all the components of Kr and Xe generated by fission that have not been destroyed are finally transferred to the off-gas system.

  Further, FIG. 1 also shows piping that takes out the reactor water from the reactor pressure vessel 10 and returns to the reactor pressure vessel 10 through the reactor water purification system 7 again.

Figure 2 shows the change of the irradiation intensity ratio of the ¹³⁸ Xe / ⁸⁸ Kr activity intensity generated in the reactor water from the combustion of natural uranium and 3.2% enriched uranium on the surface of the fuel cladding of a general boiling water reactor. It is shown as a value in the reactor water at the time of off-gas generation. Here, the recoil energy of Kr due to fission is larger than Xe and the mass number is small, so the range becomes longer. In the fission of impurity uranium in the cladding tube, ¹³⁸ Xe / The ratio of ⁸⁸ Kr is larger than that at fission. As a result, in the fission by the impurity uranium in the cladding tube, the ¹³⁸ Xe / ⁸⁸ Kr ratio is 35 or less as shown in FIG.

On the other hand, the Kr / Xe ratio originating from the adhering component is not affected by the range, so the production ratio by fission is reproduced, and the ratio of 40 or more shown in FIG. Of the adhering components, the components released due to breakage of the cladding tube are temporarily supplied to the surface of the cladding tube, and then adhere for a long period of time and are not supplied unless new damage occurs. The ¹³⁸ Xe / ⁸⁸ Kr ratio is about 50 in FIG. However, when the amount of adhesion is small, it is distributed in the range of 35 to 50 in competition with the contribution from impurities.

Based on the above results, it is possible to detect the difference in the ¹³⁸ Xe / ⁸⁸ Kr ratio value of the off-gas nuclide composition that is constantly measured in the operation plant, so that no new sampling or analysis operation is required. A method for determining whether or not a fissile nuclide is attached can be provided. As shown in FIG. 1, the reactor water and steam system in the nuclear reactor system forms a closed loop, so that all the components of Kr and Xe generated by fission that have not been destroyed are finally transferred to the off-gas system. However, since the elemental state of these fission products changes due to decay, there is a time delay due to the difference in these chemical states before reaching the off-gas system. This difference in migration behavior, when comparing the ¹³⁸ Xe / ⁸⁸ Kr ratio at generation time, for a relatively short half-life ¹³⁸ Xe, it is necessary to correct decay time correction from the generation to the measurement.

In the first embodiment, the off-gas transition time required to accurately correct the ¹³⁸ Xe / ⁸⁸ Kr ratio for evaluating the presence or absence of fissile nuclide attachment, regardless of the plant structure and operating conditions, An internal standard method that can be evaluated in various operating conditions and furnace-type plants is provided. The correction method for the off-gas composition and transition time during measurement is shown below.

The decay of the ¹³⁵ Xe isomer from the production point to the off-gas measurement point is determined by two time factors. One is the transition time t ₁ in the gas phase that reaches the off-gas measurement point via the steam from the core boiling region. The other is the transition time t ₂ of the liquid phase in which Xe produced by decay of ¹³⁵ I adsorbed to clean resin reaches the core boiling region through the reactor water from the resin. On the other hand, ¹³⁸ I has a short half-life, so it immediately decays to ¹³⁸ Xe after generation and is added to the Xe component directly generated by fission. That is, only t ₁ contributes to attenuation.

Here, if the half-lives of ^135m Xe, ^135g Xe and ¹³⁸ Xe are T _m , T _g and T ₈ , respectively, these transition times are the activity intensity A ₀ generated by fission and ¹³⁵ I decay and off-gas system. It is represented by the ratio of the radioactivity intensity A ₁ at the time of measurement.

_135m A ₁ / _135m A ₀ = A _m = 0.35 (1/2) ^{(t1 / Tm)} + 0.65 (1/2) ^{((t1 + t2) / Tm)} (1)
_{135g A 1 / 135g A 0 =} A g = 0.04 (1/2) (t1 / Tg) + 0.96 (1/2) ((t1 + t2) / Tg) (2)
_{138 A 1/138 A 0 =} A 8 = (1/2) (t1 / T8) (3)
Here, the ratio between the generated value and the measured value of each radioactivity intensity is
_{(138 A 1/138 A 0} ) _{/ (135m A 1 / 135m A} 0)
_{= (138 A 1 / 135m A} 1) / ( ₁₃₈ A ₀ / _135m A ₀ ) = C _m (4)
( _135m A ₁ / _135m A ₀ ) _{/ (135g A 1 / 135g A} 0)
_{= (135m A 1 / 135g A} 1) / ( _135m A ₀ / _135g A ₀ ) = C _g (5)
Therefore, the transition time t ₂ in the liquid phase is
(1) taking the logarithm of equation by which the (3) be approximated with T ₈ / T _m ≒ 1 is an expression obtained by multiplying the T ₈ / T _m in formula
t ₂ = −T _m (1 / log2) log (1 / 0.65 / C _m- (0.35 / 0.65)) (6)
Indicated by.

On the other hand, the transition time t ₁ in the gas phase has a small contribution of ^135m Xe to the production of ^135g Xe, so if we take the logarithm of equation (1) / (2) and substitute t ₂ in equation (6)
t ₁ = T _g T _m / (T _m -T _g ) / (log2)
log [C _g 0.04 + 0.96 (1/2) ^{((−Tm / Tg / log2) × log (1 / 0.65 / Cm−0.35 / 0.65))
/0.35+0.65(1/2} ) ^{-1 / log2log (1 / 0.65 / Cm-0.35 / 0.65))} ]] (7)
The ^135m Xe, ^135g Xe, ¹³⁸ Xe measured values and the ^135m Xe / ^135g Xe activity intensity ratio ( _135m A ₀ / _135g A ₀ ) = P _{m / g,} and the radioactivity intensity ratio ¹³⁸ Xe / ^135m Xe during generation _{(138 a 0 / 135m a 0} ) = P 8 / m is not dependent on an increase of burnup, shows a substantially constant value. For this reason, the values in the table of FIG. 3 can be applied to the radioactivity intensity ratio at the time of production of the target fuel body regardless of the burnup, and the transition time t _{1 in} the gas phase from the core to the off-gas system can be obtained.

Here, the half-life of T _K is ⁸⁸ Kr, R _m is the radioactivity intensity ratio of ¹³⁸ Xe / ⁸⁸ Kr obtained by measuring the radioactivity intensity ratio of ^135m Xe / ^{135 g} Xe during generation _(135m A ₀ / _135g a ₀₎ = P _{m / g} 7.3, radioactivity intensity ratio of _{^{138 Xe / 135m Xe (138 a}} 0 / 135m a 0) = P 8 / m values for the total amount deposited or impurities of 2 cases 3.55 and By calculating the transition time using 3.80 and substituting these values into the following equation (8), the upper and lower limits of the ¹³⁸ Xe / ⁸⁸ Kr ratio at the time of generation can be obtained.

R _p = ( ¹³⁸ Xe / ⁸⁸ Kr) = R _m · 2 ^{t1 ((1 / T8)} - ^{(1 / TK))} (8)
Calculate the transition time from off-gas generation to measurement by substituting the radioactivity intensity obtained in the conventional routine measurement into the above equation (7), and substitute this transition time into equation (8) to generate calculating the Xe / Kr ratio R _p when. When there is no adhesion on the surface of the cladding tube, R _p falls within the range of 35 ± 5 including errors in radiation measurement. On the other hand, when there is adhesion on the surface of the cladding tube, R _p shows a value of 40 or more, so that the origin of off-gas can be evaluated and the presence or absence of adhesion of fissile components on the surface of the cladding tube can be determined.

In the above explanation, an example is shown in which ⁸⁸ Kr is used for evaluation, but ⁸⁷ Kr can be used instead of ⁸⁸ Kr.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. However, parts that are the same as or similar to those in the first embodiment are denoted by common reference numerals, and redundant description is omitted.

  FIG. 4 shows the process of producing iodine isotopes in the reactor water measured routinely. Among the five iodine isotopes, the concentrations of mass numbers 135 and 134 reflect the chemical properties of iodine, but the concentration of mass number 132 is generated by the decay of Te-132 with a long half-life. The value reflects the behavior of.

  As shown in FIG. 5, I and Te are generated in the reactor core 1 and dissolved and volatile iodine is transferred to the reactor water purification system 7 and partly transferred to the steam system 3 by carryover. Thereafter, it is removed by the condensate purification system 6. On the other hand, since Te is not volatile and is mostly removed by the reactor water purification system 7, the purification coefficients are different between the two. The removal of elements by the reactor water purification system 6 targets components dissolved or transferred to the reactor water, so the element purification coefficient correlates with solubility and becomes an index representing the degree of adhesion to the cladding surface. In addition, it is possible to know the change in the existence state of elements in the reactor water from this fluctuation.

Therefore, if the number of iodine atoms in the reactor water is Z, the release rate (atoms / s) is R, and the decay constant is λ, the total purification coefficient of iodine β (s ^-1 ) is
dZ / dt = R ‐Z ・ (λ + β) (9)
It becomes. R in equation (9) is
R = Z ・ λ ・ (λ + β) / λ (10)
When the radioactivity intensities 134 and 135 are substituted into equation (10), the ratio between the two is represented by equation (11).

R _134I / R _135I
= (λ _134I + β) / λ _134I・ Z _134I・ λ _134I / (λ _135I + β) / λ _135I・ Z _135I・ λ _135I (11)
Since the ratio of both is replaced by the ratio of the fission yield and the decay constant in a plant without cladding failure, Equation (11) is rewritten as follows, and the radioactivity concentration of each isotope in the reactor water is C:
_c Y _134I / _c Y _135I
= (λ _134I + β) ・ λ _135I / (λ _135I + β) ・ λ _134I・ (C _134I / C _135I ) (12)
Is obtained. Here, the total purification coefficient β of iodine is expressed by the following equation (13).

On the other hand, when the total purification coefficient α of Te is expressed by the ratio of the fission yield in the same manner as in the equation (12), and the mass number 132 and 135 are indicated by the accumulated fission yield _c Y,
_c Y _132Te / _c Y _135I
= ((λ _132Te + α) ・ λ _135I ) / ((λ _135I + β) ・ λ _132Te ) ・ (C _132Te / C _135I ) (14)
Here, since the iodine concentration of mass number 132 is composed of a component generated by direct fission and a component generated by the decay of Te-132, if the concentration component generated by direct fission is ^F C _132I
i Y _132I / _c Y _135I
= ((λ _132I + β) ・ λ _135I ) / ((λ _135I + β) ・ λ _132I ) ・ ( ^F C _132I / C _135I ) (15)
^F C _132I
= C _135I・ ( _i Y _132I / _c Y _135I ) ・ ((λ _135I + β) ・ λ _132I ) / ((λ _132I + β) ・ λ _135I ) (16)
Here, _i Y _132I represents the sum of individual fission yields in which ^132m I and ¹³² I are directly generated.

The ¹³² I and ¹³² Te concentrations produced by the decay of ¹³² Te in the steady state are
C _132Te = (λ _132I + β) ・ (C _132I ^-F C _132I ) / λ _132I (17)
Therefore, the total purification coefficient α of Te can be calculated by the following equation (18) from the equations (14) and (17).

  The fission yields used in equations (13) and (18) are almost constant during the operation period except for the initial stage of combustion regardless of the plant, and therefore the values shown in the table of FIG. 6 for all plants. Can be used. If the purification factor of the element obtained here is the same as the purification factor of the reactor water, all the elements are present in the reactor water and no adhesion to the wall of the vessel or the like has occurred. If it is smaller than the water purification coefficient, it means that it adheres to the surface of the structural material. Therefore, the characteristics of the element can be found from the ratio of the purification coefficient of the element to the reactor water. Change in elemental behavior can be known.

  In any of the methods of the embodiments described above, it is preferable that the actual calculation process is executed by a computer.

A schematic system diagram for explaining the generation and migration behavior of Xe in a boiling water reactor. The graph which shows the change with respect to irradiation time of the ¹³⁸ Xe / ⁸⁸ Kr activity intensity ratio in the reactor water at the time of off gas production. The table | surface which shows the value used by Formula (6), (7), (8) of fissile nuclide adhesion determination. Explanatory drawing which shows the production | generation process of the iodine isotope in a reactor water. A schematic system diagram for explaining the behavior of I and Te in the reactor water of a boiling water reactor. The table | surface which shows the value used by the purification coefficient calculation formula (13) and (18) of iodine and tellurium.

Explanation of symbols

1: Reactor core 2: Reactor water 3: Steam system 4: Condenser 5: Off gas system 6: Condensate purification system 7: Reactor water purification system 8: Steam turbine 10: Reactor pressure vessel

Claims (4)

In the element deposition evaluation method on the surface of the fuel cladding of an operating nuclear power plant,
Of the off-gas nuclides of the operating nuclear power plant, the radioactivity intensity ratio of the nuclides Xe-135m, Xe-135, Xe-138 and Kr-88, or Xe-135m, Xe-135, Xe-138 and Kr- The radioactivity intensity ratio of 87 nuclides was determined by measurement, the composition ratio of the above nuclides was determined based on this radioactivity intensity ratio, and the off-gas / iodine transition time in the furnace was evaluated based on this composition ratio. A method for evaluating element adhesion on the surface of a fuel cladding tube, wherein the presence or absence of adhesion of fissile nuclides is determined based on the time of iodine transfer into the furnace. In the element deposition evaluation method on the surface of the fuel cladding of an operating nuclear power plant,
Of the iodine isotopes in the reactor water of the operating nuclear power plant, the radioactivity intensity ratio of I-132, I-134 and I-135 nuclides was determined by measurement, and the composition of the above nuclide was determined based on this radioactivity intensity ratio. Based on this composition ratio, calculate the reactor water purification system coefficient of Te at the operating nuclear power plant, and based on this Te reactor water purification system coefficient, the fissile nuclide on the outer surface of the fuel rod An element adhesion evaluation method on the surface of a fuel cladding tube, characterized by determining a variation in adhesion of the fuel. A program for causing a computer to evaluate the adhesion of elements on the surface of a fuel cladding of an operating nuclear power plant,
Of the off-gas nuclides of the operating nuclear power plant, the radioactivity intensity ratio of the nuclides Xe-135m, Xe-135, Xe-138 and Kr-88, or Xe-135m, Xe-135, Xe-138 and Kr- Based on the result of measurement of the radioactivity intensity ratio of 87 nuclides, the composition ratio of the above nuclides was determined, and based on this composition ratio, the transition time of the off-gas and iodine in the furnace was evaluated, A program for evaluating element adhesion on the surface of a fuel cladding tube, wherein the computer functions so as to determine the presence or absence of fissile nuclide adhesion based on the transition time. A program for causing a computer to evaluate the adhesion of elements on the surface of a fuel cladding of an operating nuclear power plant,
Of the iodine isotopes in the reactor water of the operating nuclear power plant, the composition ratio of the above nuclides is determined based on the result of the measurement of the radioactivity intensity ratio of the nuclides of I-132, I-134 and I-135, Based on this composition ratio, calculate the reactor water purification system coefficient of Te at the operating nuclear power plant, and based on this Te reactor water purification system coefficient, fluctuating fissile nuclide deposition on the fuel rod outer surface A program for evaluating element adhesion on the surface of a fuel cladding tube, wherein the computer is operated so as to determine

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