GB/T 11813-1996 Helium mass spectrometry leak detection for pressurized water reactor fuel rods
Some standard content:
GB/T 11813—1996
Fuel rod sealing performance Nitrogen mass spectrometry leak detection technology is one of the important inspection items in the fuel rod manufacturing process. GB11813-89, issued in December 1989, was written based on the nitrogen mass spectrometry leak detection technology used in the manufacture of 300MW fuel rods. This standard was implemented in the production of the first 300MW Qinshan reactor and the first refueling assembly. It is of great significance to ensure the sealing performance of fuel elements. In the early 1990s, my country began to manufacture large-scale nuclear power plant fuel assemblies, which put forward higher requirements for fuel rod leak detection technology, and it was necessary to improve the leak detection method, equipment, standard leak holes and data processing methods. The improved leak detection method has been implemented in the production of the first refueling of the 900MW reactor of Daya Bay Nuclear Power Plant and the second refueling assembly of the 300MW reactor of Qinshan Nuclear Power Plant. The results show that the new method has greater superiority and reliability. Therefore, it is necessary to revise the original GB11813-89 to make my country's nuclear fuel element leak detection technology more perfect. This standard shall replace GB11813-89 from the date of implementation. Appendix A and Appendix B of this standard are both appendices of the standard. This standard was proposed by China National Nuclear Corporation. This standard is under the jurisdiction of the Nuclear Industry Standardization Institute. The drafting unit of this standard: State-owned August 12 Factory. The main drafter of this standard: Zhu Guosheng.
1 Scope
National Standard of the People's Republic of ChinabZxz.net
Helium leak testing of nuclear fuel rod for PWRGB/T11813—1996
Replaces GB11813-89
This standard specifies the method, steps and calculation and judgment of the sealing performance of pressurized water reactor fuel rods (hereinafter referred to as "fuel rods") using ammonia mass spectrometry leak detection technology for non-destructive testing. This standard is applicable to the sealing performance testing of pressurized water reactor fuel rods, and the detection leakage rate range is 1×10-11Pa·m/s~~1×10-7Pa·m'/s.
This standard is also applicable to the leak detection of the sealing performance of pressurized water reactor control rods, burnable poison rods, neutron source rods, etc. 2 Definitions
This standard adopts the following definitions.
2.1 Direct helium leak testing Direct helium leak testing is a method of testing the sealing performance using the nitrogen filled during the manufacture of the fuel rods as the leak-indicating gas. 2.2 Immersed helium leak testing Fuel rods are placed in a vacuum container and filled with nitrogen at a certain pressure, so that ammonia enters the interior from the leak holes or gaps in the fuel rods, and then nitrogen mass spectrometry leak detection is performed.
2.3 The maximum time of leaking When the fuel rods are leaking or there are penetrating defects in the cladding tubes and end plugs, the time from the nitrogen filling and sealing welding to the leakage rate that can be detected by the ammonia mass spectrometer leak detector is scrapped. The maximum leak time is determined according to Appendix B (Appendix to the standard). 3 Method Summary
This standard is based on the principle of mass spectrometry analysis technology. It uses ammonia mass spectrometer leak detector, detection device, vacuum system, standard leak hole, etc. to detect the sealing performance of fuel rods. According to the allowable leak rate specified in the fuel rod design technical conditions for sealing performance and the measurement deviation of the leak detection system, the fuel rod leakage rate scrap limit is determined according to Appendix A (Appendix to the standard). When the leak rate is less than the scrap limit, the fuel rod sealing performance is qualified; otherwise, it is unqualified.
4 Materials and Equipment
4.1 Leakage gas nitrogen.
4.2 Liquid nitrogen Industrial liquid nitrogen.
4.3 Fluorine gas Industrial nitrogen.
4.4 The sensitivity of the nitrogen mass spectrometer leak detector is better than 1×10-11Pa*m2/s, and the range is 1×10-11～1×10-7Pa·m/s. 4.5 The standard leak hole adopts a quartz film ammonia-impregnated series standard leak hole with an ammonia chamber, and the leak rate range is within the leak rate order of magnitude allowed by the fuel rod technical conditions.
4.6 Compound vacuum gauge
The maximum range is 1×10-5Pa.
Approved by the State Administration of Technical Supervision on December 19, 1996 and implemented on December 1, 1997
GB/T 11813-1996
4.7 Leak detection device and vacuum system The vacuum degree of the leak detection container must reach 1×10-3Pa. The leak detection system is shown in Figure 1.
4.8 The volume of the nitrogen-filled sealed container is the same as that of the leak detection container, and it is equipped with a low vacuum pump, a pressure gauge and a nitrogen source. 5 Detection steps
5.1 Preparation
5.1.1 Start the leak detector according to the steps in the operating instructions of the nitrogen mass spectrometer leak detector (4.4). 5.1.2 Close the sealing end cap of the leak detection container, start the mechanical pump MP? to pre-vacuum, connect the diffusion pump DP2 heating system, and when the leak detection container reaches 6Pa, close V,, open V. and V:, and use the diffusion pump DP2 to vacuum the container. 5.1.3 Inject liquid (4.2) into the instrument cold trap and continue to vacuum the mass spectrometer chamber of the leak detector. 5.1.4 Adjust the emission current of the mass spectrometer chamber, generally between 0.2mA and 2mA: 5.1.5 When the leak rate output meter indicates the range of 10-11Pa·m\/s, adjust the output zero point. 5.1.6 Open the V: valve and the leak detection platform valve on the instrument according to the mass spectrometer operating instructions, and use the standard hole (4.5)F to adjust the nitrogen peak. VM
Vi.V. — vacuum valve, MSP-ammonia mass spectrometer leak detector; DP,, DPz-oil diffusion pump; MP1, MP2-mechanical vacuum pump; Fi, F2, F--ammonia standard hole D, a thermocouple vacuum gauge; Dz-ionization gauge, VM-compound vacuum gauge; Na-nitrogen bottle; CH-detection container; PM-pressure gauge Figure 1 Schematic diagram of fuel rod nitrogen mass spectrometer leak detection system 5.1.7 Turn on the power of the compound vacuum gauge (4.6). When the vacuum degree of the container reaches 9X10-3Pa, open the valve V of the standard leak hole F and the connecting valve Va, and close V. After the valve, start timing at the same time. After about 1 minute, the output indication value gradually stabilizes. Adjust the calibration knob so that the leakage rate meter indication value reaches the nominal value of the standard leak hole. 5.1.8 Use the standard leak hole F2 to verify the instrument according to the steps in 5.1.7, but do not adjust the calibration knob to confirm whether the output value is within the specified range.
5.1.9 Measure the background output value of the detection system. The background output value shall not approach or exceed the fuel leakage rate scrap limit determined in Appendix A (Appendix of the standard). Otherwise, the leak detection container and mass spectrometer room shall be cleaned. 5.2 Fuel rod leak detection
5.2.1 Direct leak detection method
5.2.1.1 Turn off V., V., Vi.V., cut off the power supply of the compound vacuum gauge VM, turn on Vs, inject nitrogen (4.3) into the container, and when the pressure gauge PM indicates a value of 1×105Pa, immediately turn off V:, open the sealing end cover of the leak detection container CH, push the stainless steel tank containing fuel rods (the number is determined according to the volume of the stainless steel tank in GB/T 11813--1996) into the container, and close the sealing end cover. 5.2.1.2 Evacuate the container in accordance with 5.1.2. 5.2.1.3 Turn on the power of the compound vacuum gauge (4.6). When the vacuum degree of the container reaches 9×10-3Pa, turn on V and turn off V. Start timing for about 1 minute. After the output value reaches stability, make a record. If the output indication value is less than the scrap limit, the sealing performance of the batch of fuel rods is qualified. Otherwise, the half-split method should be used and the steps in 5.2.1 should be followed again until the leaking fuel rods are found. 5.2.2 Back pressure leak detection method
5.2.2.1 Use the back pressure leak detection method for fuel rods that exceed the maximum leakage time. The maximum leakage time of fuel rods shall be determined according to Appendix B (Standard Appendix).
5.2.2.2 Place the fuel rods in a dedicated sealed container (4.8). After evacuating to 10-2MPa, fill the container with nitrogen (4.1) of not less than 0.2MPa and keep it for about 30 minutes. 5.2.2.3 Take out the fuel rods from the container and perform surface nitrogen removal and purification. You can use an electric fan, clean compressed air or nitrogen to blow the surface of the fuel rods for about 10 minutes.
5.2.2.4 Follow 5.2.1.1~~5.2.1.3. Perform leak detection on fuel rods. 6. Record and report of test results
The test record includes the following contents:
a) Model of mass spectrometer;
b) Number and leak rate of standard leak hole;
c) Model, batch number, rod number and quantity of fuel rods;
d) Limit of rejection of leakage output signal of fuel rods;
e) Output signal value of standard leak hole;
f) Background signal output value of leak detection system;
g) Leak detection output value of fuel rods;
h) Whether fuel rods are qualified:
i) Leak detector calibration output value;
j) Operator signature and test date.
GB/T 11813—1996
Appendix A
(Appendix to the standard)
Determination of the scrap limit of the leakage rate of fuel rods
A1Operate the leak detection device according to steps 5.1.1 to 5.1.6. A2
Repeat the measurement of the standard leak holes F1 and F2 for 10 times according to steps 5.1.7 to 5.1.8, and record the output indication value. Calculate the output indication average value and standard deviation of the standard leak holes F1 and F2 respectively. A3
A4Calculate the scrap limit of the fuel rod leakage output indication value according to the following formula. RL
S2- S,
× SPL+ B- 3a
Wherein: RL-—Fuel rod leakage output indication value scrap limit, Pa·m\/s; S,—Standard leak hole F, output indication average value, Pa·m\/s;—Standard leak hole F. Output indication average value, Pa·m\/s; S.
F,Standard leak hole F, nominal leakage rate, Pa·m/s; F2-——Standard leak hole F2 nominal leakage rate, Pa·m\/s; SPL-—Allowable leakage rate given by fuel rod technical conditions, Pa·m\/s, B-—Background signal output value of leak detection system, Pa·m\/s; -Standard deviation.
Wherein: a——F, standard deviation of output indication value, Pa·m\/s; 02——F, standard deviation of output indication value, Pa·m\/s. 280
（A1）
（A2）
B1 Sample preparation
GB/T11813—1996
Appendix B
(Appendix to the standard)
Determination of the longest leakage time of fuel rods
Take a number of fuel rods produced by normal process (3~4 are recommended), cut off the sealing welds at the ends at the same time, so that the nitrogen in the rods can be released naturally, or the fuel rods are not welded with the upper plug ring seam, and nitrogen is directly filled. B2 Sample measurement
B2.1 The materials and equipment shall comply with the requirements of 4.1~4.7. B2.2 According to the steps of 5.1~5.2, one of the sample rods shall be measured. If the output value is greater than the scrap limit RL value specified in A4, re-measure according to the above steps after a period of time. If it is close to the RL value, another sample rod should be replaced for testing until the initial test result of one of the rods is close to the scrap limit RL value. The time from the preparation of the sample rod to this time is the longest leakage time of the fuel rod. Fuel rods with a leakage time less than the longest leakage time can be leaked by the direct leak detection method, otherwise they can be leaked by the back pressure leak detection method.
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