Method for calculating pressure in radioactive substance transportation container

Abstract

The invention relates to a method for calculating pressure in a radioactive substance transportation container. The method comprises the following steps of: determining whether leakage exists on a containing boundary in the radioactive substance transportation container or not; calculating the pressure in the container and the corresponding time according to whether leakage exists in the containing boundary or not; according to the method for calculating the pressure in the radioactive substance transportation container, the time needed when the pressure in the container reaches the preset value is determined, and the time needed when the pressure in the container reaches the preset value can be obtained according to different conditions. Moreover, the method for calculating whether the single-layer containment boundary leaks or not under different conditions is considered, and the method can also be referenced and popularized for the working condition of the multi-layer containment boundary.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive material transportation, and in particular relates to a method for calculating the internal pressure of a radioactive material transportation container. Background Art

[0002] During the use of radioactive material transport containers, gases such as hydrogen will be generated in the cargo package due to thermal decomposition and radiolysis. As the gas accumulates, the pressure inside the cargo package increases. When the pressure exceeds the design pressure, the cargo package may be damaged, causing harm to personnel and accidents. Summary of the invention

[0003] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for calculating the pressure inside a radioactive material transport container, which can obtain the relationship between the pressure change inside the cargo package and time.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a method for calculating the pressure inside a radioactive material transport container, comprising the steps of: determining whether there is a leakage in the containment boundary inside the radioactive material transport container; calculating the pressure inside the container and the corresponding time based on whether there is a leakage in the containment boundary; and determining the time required for the container to reach a predetermined pressure.

[0005] Furthermore, whether the inclusion boundary has leakage is specifically: a single-layer inclusion boundary has leakage and a single-layer inclusion boundary has no leakage.

[0006] Furthermore, when the single-layer containment boundary has no leakage, the ideal gas law is used to describe the change of container pressure over time.

[0007] Furthermore, when the single-layer containment boundary has no leakage, the corresponding relationship between the pressure in the container and the time is:

[0008]

[0009] Where: R g is the gas law constant; V is the effective volume in the container; T 0 is the initial temperature of the container; P 0 is the initial pressure of the container; R M is the molar generation rate of the gas; T is the time after the container is sealed.

[0010] Furthermore, when there is leakage in the single-layer containment boundary, the corresponding relationship between the pressure in the container and the time is:

[0011]

[0012] Where V is the void volume of the container, cm 3 ; R g is the gas law constant; RM is the molar generation rate of the gas; T 0 is the initial temperature of the container; T is the steady-state temperature in the container; P 0 is the initial pressure of the container; F c is laminar flow rate; P u is the internal pressure of the container; P d is the external pressure of the container.

[0013] Furthermore, when there is leakage in the single-layer containment boundary, the steady-state pressure in the container is:

[0014]

[0015] Among them, P ss is the steady-state pressure in the container; R g is the gas law constant; R M is the molar generation rate of the gas; F c is laminar flow rate; F M is the molecular flow rate; M is the effective viscosity of the gas; T is the steady-state temperature in the container; M W is the effective molecular weight of the gas.

[0016] Furthermore, the method of determining the time required for the container to reach a predetermined pressure specifically comprises: calculating the corresponding relationship between the pressure in the container and the time according to different leakage conditions, and then calculating the time required for reaching the predetermined pressure.

[0017] The effect of the present invention is that the time required for the pressure in the container to reach a predetermined value can be obtained according to different situations. In addition, the calculation method under different situations of whether a single-layer containment boundary leaks is considered, and the working conditions of multi-layer containment boundaries can also be referred to and extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flowchart of the steps of a method for calculating the pressure inside a radioactive material transport container. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown, the present invention proposes a method for calculating the pressure inside a radioactive material transport container, comprising the steps of:

[0021] S1, determine whether there is leakage in the containment boundary of the radioactive material transport container;

[0022] Specifically, based on whether the radioactive material transport container has leakage or not, before calculating the internal pressure thereof, subsequent pressure change calculations are performed according to different situations.

[0023] In this embodiment, the inclusion boundary of the reflective transport container is a single-layer inclusion boundary, and whether the inclusion boundary has leakage is specifically: the single-layer inclusion boundary has leakage and the single-layer inclusion boundary has no leakage.

[0024] S2, calculating the pressure inside the container and the corresponding time according to whether there is leakage at the containment boundary;

[0025] Specifically, after determining the number of containment boundary layers of the cargo package and whether there is leakage, the pressure inside the container and the corresponding time are calculated according to whether there is leakage.

[0026] For a single-layer containment boundary with no leakage, the ideal gas law can be used to describe the change of container pressure over time:

[0027]

[0028] Where: P u (t) = pressure in the container at time t, atm;

[0029] n 0 = the initial number of moles of gas in the container, mol;

[0030] R M = molar production rate of gas, mol / s;

[0031] t = time after container sealing, s;

[0032] R g = Gas law constant, 82.05 cm 3 ·atm / (mol·K);

[0033] T = temperature of the container, K;

[0034] V = effective volume in the container, cm 3 .

[0035] If the container is initially at pressure P 0 and temperature T 0 The initial gas mole number n 0 for:

[0036]

[0037] Where: n 0 = the initial number of moles of gas in the container, mol;

[0038] R g = Gas law constant, 82.05 cm 3 ·atm / (mol·K);

[0039] V = effective volume in the container, cm 3 ;

[0040] T 0 = initial temperature of the container, K;

[0041] P 0 = initial pressure of the container, atm;

[0042] Substituting (2) into (1), we can obtain the relationship between pressure and time in a single-layer containment boundary container with no leakage path:

[0043]

[0044] Where: R g = Gas law constant, 82.05 cm 3 ·atm / (mol·K);

[0045] V = effective volume in the container, cm 3 ;

[0046] T 0 = initial temperature of the container, K;

[0047] P 0 = initial pressure of the container, atm;

[0048] R M = molar production rate of gas, mol / s;

[0049] t = time after container sealing, s.

[0050] For the case where there is a leakage path in a single-layer containment boundary, the equation for the change of pressure in the container with time is:

[0051]

[0052] Where V = void volume of the container, cm 3 ;

[0053] R g = Gas law constant, 82.05 cm 3 ·atm / (mol·K);

[0054] R M = molar production rate of gas, mol / s;

[0055] T 0 = initial temperature of the container, K;

[0056] T = steady-state temperature in the container, K;

[0057] P 0= initial pressure of the container, atm;

[0058] F c = laminar flow rate, cm 3 / s·atm;

[0059] P u = pressure inside the container, atm; atm.

[0060] P d = pressure outside the container, atm;

[0061] Assuming that the time is infinite, the steady-state pressure in the container is:

[0062]

[0063] P ss = steady-state pressure in the container, atm;

[0064] R g = Gas law constant, 82.05 cm 3 ·atm / (mol·K);

[0065] R M = molar production rate of gas, mol / s;

[0066] F c = laminar flow rate, cm 3 / s·atm;

[0067] F M = molecular flow rate, cm 3 / s·atm;

[0068] m=Gas effective viscosity, mPa·s,

[0069] T = steady-state temperature in the container, K;

[0070] M W =Effective molecular weight of gas.

[0071] S3, determining the time required for the container to reach a predetermined pressure;

[0072] Specifically, after the corresponding relationship between the pressure in the container and the time is calculated according to different leakage situations, the time required to reach the predetermined pressure can be calculated.

[0073] Let's take a specific example as an example:

[0074] 1. Calculation of the time required for the pressure in a single-layer containment boundary leak-free container to reach 2 atmospheres:

[0075] Consider a container at pressure P0 =1atm and temperature T 0 = Sealed at 298K. The gas generation rate in the container is 3.1E-6 mol / s, the container temperature is 363K, and the container void volume is 5000cm 3 .

[0076] R M =3.1E-6mol / s, P 0 =1atm, T=363K, T 0 =298K, V=5000cm 3

[0077] Substitute into formula (3)

[0078]

[0079] It can be seen that it takes 42162s for the pressure in the container to reach 2 atmospheres.

[0080] 2. Pressure calculation of a container with a single-layer containment boundary and a leakage path

[0081] Consider a container at pressure P 0 =1atm and temperature T 0 = 298K (25℃) sealed, the container has a leak hole with a length of 0.5cm and a diameter of 3.2E-3cm, the steady-state temperature of the container is 80℃, the effective molecular weight of the gas in the container at any time can be approximated to 26g / mol, the gas generation rate in the container is 2.073E-7mol / s, and the laminar flow rate is 2.487E-2cm 3 / s·atm, the molecular flow rate is 9.201E-4cm3 / s·atm, assuming that the downstream pressure is one atmosphere and the container void volume is 1000cm 3 , calculate the steady-state pressure of the container:

[0082] R M =2.073E-7mol / s, P 0 =1atm, P d =1atm, T=353K, T 0 =298K, V=1000cm 3 , R g =82.05cm 3 ·atm / (mol·K), F c =2.487E-2cm 3 / s·atm,Fm=9.201E-4cm 3 / s·atm.

[0083] Substitute into the formula

[0084]

[0085] It can be seen from the above embodiments that the present invention can obtain the time required for the pressure in the container to reach a predetermined value according to different situations. In addition, the calculation method under different situations of whether a single-layer containment boundary leaks is considered, and the working conditions of multi-layer containment boundaries can also be referred to and extended.

[0086] The present invention is not limited to the embodiments described in the specific implementation manner. Those skilled in the art may derive other implementation manners based on the technical solution of the present invention, which also fall within the technical innovation scope of the present invention.

Claims

1. A method for calculating the pressure inside a radioactive material transport container, characterized in that: Includes steps: Determine if there are leaks in the containment boundaries of radioactive material transport containers; Calculate the pressure inside the container and the corresponding time according to whether there is leakage in the containment boundary; Determine the time required for the container to reach a predetermined pressure.

2. A method for calculating the pressure inside a radioactive material transport container according to claim 1, characterized in that: Whether there is leakage in the inclusion boundary is specifically: a single-layer inclusion boundary has leakage and a single-layer inclusion boundary has no leakage.

3. A method for calculating the pressure inside a radioactive material transport container according to claim 2, characterized in that: When the single-layer containment boundary has no leakage, the ideal gas law is used to describe the change of container pressure over time.

4. A method for calculating the pressure inside a radioactive material transport container as claimed in claim 3, characterized in that: When the single-layer containment boundary has no leakage, the corresponding relationship between the pressure in the container and the time is: Where: R g is the gas law constant; V is the effective volume in the container; T0 is the initial temperature of the container; P0 is the initial pressure of the container; R M is the molar generation rate of the gas; T is the time after the container is sealed.

5. A method for calculating the pressure inside a radioactive material transport container as claimed in claim 3, characterized in that: When there is leakage in the single-layer containment boundary, the corresponding relationship between the pressure in the container and time is: Where V is the void volume of the container, cm 3 ; R g is the gas law constant; R M is the molar generation rate of the gas; T0 is the initial temperature of the container; T is the steady-state temperature in the container; P0 is the initial pressure of the container; F c is laminar flow rate; P u is the internal pressure of the container; P d is the external pressure of the container.

6. A method for calculating the pressure inside a radioactive material transport container as claimed in claim 5, characterized in that: When there is leakage in the single-layer containment boundary, the steady-state pressure in the container is: Among them, P ss is the steady-state pressure in the container; R g is the gas law constant; R M is the molar generation rate of the gas; F c is laminar flow rate; F M is the molecular flow rate; M is the effective viscosity of the gas; T is the steady-state temperature in the container; M W is the effective molecular weight of the gas.

7. A method for calculating the pressure inside a radioactive material transport container according to claim 1, characterized in that: The method of determining the time required for the container to reach the predetermined pressure specifically comprises: calculating the corresponding relationship between the pressure and time in the container according to different leakage conditions, and then calculating the time required for reaching the predetermined pressure.

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