Cryogenic System Commissioning Summary Report 2019年1月17日 Cryogenic System Commissioning Summary Report He Kun , He Chongchao, Ding Meiying, Zhang Yu, Wang Yaqiong, Li Na, and Ye Bin June 5, 2018

Content Introduction Commissioning procedures of cryogenic system Acceptance testing of helium refrigerator Commissioning of hydrogen cycle Summary and questions

Introduction Purpose of cryogenic: Providing supercritical cryogenic hydrogen to neutron moderators, working at 14~15 bara, 17-20 K. Hydrogen critical temperature is 32.94 K, and critical pressure is 12.84 bara. Main equipment: Helium refrigerator with capacity of 2200W@20K. Hydrogen cycle, include hydrogen loop cold-box(two cryogenic hydrogen pump, hydrogen-helium heat exchanger, ortho-para convertor, heater and so on) Accumulator cold-box; Cryogenic pipes.

Cryogenic system flow diagram Introduction Cryogenic system flow diagram

Introduction Compressor and oil separator Storage tank Helium cold-box Hydrogen cycle cold-box and accumulator cold-box

Commissioning procedures of cryogenic system 2019年1月17日 Commissioning procedures of cryogenic system 1. Acceptance testing on the helium refrigerator was completed in August, 2016, after the installation of the helium refrigerator. 2. After installation of hydrogen loop equipment and simulated load, hydrogen loop uses helium instead of hydrogen and cooled down to 20 K from January to April, 2017. Then, hydrogen loop using hydrogen as working medium, cooled to 20 K, from April to May. 3. After removing the simulated load, cryogenic system and moderators are jointed commissioning on June, 2017. In order to ensure personal and device safety, excellent safety interlock is the precondition.

Acceptance testing of helium refrigerator Compressor, oil separator and helium cold-box are installed on July, 2016. In order to ensure proportion of the impurity under 5 PPM and total under 10 PPM, activated carbon need thermal desorption and liquid nitrogen purifier need to purify. Using the refrigerator internal heater as thermal load. The outlet of turbo temperature set 16 K, running 24 hours stable, and the capacity is 2300W@20K. Refrigerating capacity /W Discharge pressure /bara Suction pressure Post-expansion temperature /K temperature / bara Flow /g/s 700 8.64 1.541 14.5 1.76 83.8 1400 10.11 1.798 14.9 2.01 96 2300 11.86 1.97 15.8 2.25 104

Acceptance testing of helium refrigerator Helium refrigerator running state at 2300 W

Commissioning of hydrogen cycle In early January 2017, cryogenic system installation have been finished. Simulated load was used instead of neutron moderator, simulating the heat load of neutron moderator. Heat load of two neutron moderators corresponding to 200kW proton beams which is CSNS design objective is 320W and 240W, respectively. In order to ensure safe, commissioning work is divided into two steps. First, hydrogen loop uses helium instead of hydrogen, cooling down to 20K, and get preliminary control logic. Second, uses hydrogen as working medium, optimized the control logic.

Commissioning of hydrogen cycle From January to April, we have completed the five rounds cool down commissioning of helium, and three rounds commissioning of hydrogen on April and May. Cryogenic system running pressure is 14-15 bar, and rupture disk pressure is 17 bara. The differential pressure of accumulator must below 1.5 bar. Therefore, pressure control is the key of commissioning. 。

Commissioning of hydrogen cycle First round of helium commissioning When Hydrogen cycle pressure increase, control logic have no venting logic at that time. Therefore, pressure fluctuate rapid cause chain protection. Second round of helium commissioning Modifying control logic, including venting and so on. In addition, needle valves were installed to reduce inlet gas flow. However, the differential pressure too high cause chain protection.

Commissioning of hydrogen cycle Third round of helium commissioning Modifying control logic, reducing differential pressure is the key work. Though differential pressure was also rapid, we control the differential pressure in reasonable range by valve and we get success. Fourth round of helium commissioning Further optimize the logic and cooling down smoothly. Fifth round of helium commissioning Further optimize the logic so that cooling down to 20 K by one key.

Commissioning of hydrogen cycle summary： We mastery how to control pressure by five round commissioning. We do leakage detecting by helium mass spectrographic method after commissioning. It prove that cryogenic system manufacture and install excellent.

Commissioning of hydrogen cycle pressure Frequency of pump Temperature of exchange outlet Temperature of exchange inlet Flow Cooling curve of helium commissioning

Commissioning of hydrogen cycle Control interface of helium commissioning

Commissioning of hydrogen cycle The volume of hydrogen cycle is 140L. physical property of hydrogen and helium have great difference. Helium density changes evenly from 300 K to 20 K. Hydrogen density changes rapidly, from 35 K to 32 K. It makes cooling down difficult. Density (kg/m3) 300 K 35 K 32 K 20 K helium 2.4 35.7 hydrogen 1.2 20.6 51.9 72.9

Commissioning of hydrogen cycle First round of hydrogen commissioning In the beginning, cooling down was smooth from 300 K to 35 K. When exchanger outlet temperature is below 35 K, pressure changes rapidly, and it makes venting frequently. At last, cooling down is fail. Second round of hydrogen commissioning We try to make all the temperature point of hydrogen cycle are 35 K-40 K. Therefore, we set helium refrigerator 60 K. The refrigerator can’t maintain 60K, and temperature drop to below 35 K. This round commissioning is fail too, but we found that all the temperature point at 35 K-40 K will get high flow.

Commissioning of hydrogen cycle Third round of hydrogen commissioning In order to maintain refrigerator temperature 35 K, we close cold-box refrigeration mode when temperature is 35 K, and it makes all the temperature point of hydrogen cycle is 35 K-40 K successful. In this case, all the temperature point of hydrogen cycle drop to 20 k slowly, and cooling down success.

Commissioning of hydrogen cycle Frequency of pump Temperature of exchange outlet pressure Temperature of exchange inlet flow Cooling curve of hydrogen commissioning

Commissioning of hydrogen cycle Control interface of hydrogen commissioning

Commissioning of hydrogen cycle After hydrogen commissioning success, we remove the simulated load, and connect the neutron moderators. Cooling down method is same to third round commissioning. Cryogenic system run four weeks from August to September stably.

Commissioning of hydrogen cycle Frequency of pump pressure flow Temperature of exchange inlet Temperature of exchange outlet Cooling curve of hydrogen commissioning on August

Commissioning of hydrogen cycle Control interface of hydrogen commissioning

Commissioning of hydrogen cycle Cryogenic system run stably last December to now, proportion of the impurity maintain low。 proportion of the impurity on 15th, May

2019年1月17日 Summary and questions Summary ： Cryogenic system commissioning work plans early, and commissioning procedures is reasonable. Though commissioning time is urgent, we get the cooling method by several round commissioning. We attach importance to the safety of the hydrogen, and chain protection works well. During the commissioning, there is no safety accident. During the commissioning, all the equipments works well, and it prove that equipments are reliable.

2019年1月17日 Summary and questions Questions ： Refrigerator must be upgraded to ensure that refrigerator can maintain 35 K for long time. We have communicated with Linde to solve this problem. The flow resistance of ortho-para convertor is too high because of too much catalyzer, and the pressure drop is more than 1bar. On the premise of enough catalyzer, We need to optimize structure and decrease catalyzer to reduce flow resistance.

Thank you！