Process and apparatus for separating and recovering krypton-85 from exhaust gas of nuclear reactor or the like

Claim 2

A PROCESS FOR INCREASING THE CONCENTRATION OF KRYPTON-85 IN AN EXHAUST GAS CONTAINING KRYPTON-85 COMPRISING PASSING A MIXTURE OF DESORBED KRYPTON-85 OBTAINED FROM A FIRST ADSORPTION BED AND SAID EXHAUST GAS INTO A SECOND ADSORPTION BED ARRANGED IN A PARALLEL WITH RESPECT TO SAID FIRST ADSORPTION BED UNTIL SUBSTANTIALLY ALL OF THE KRYPTON-85 ADSORBED IN SAID FIRST ADSORPTION BED IS TRANSFERRED TO SAID SECOND ADSORPTION BED, AND THEREAFTER TRANSFERRING A MIXTURE OF SAID EXHAUST GAS AND THE KRYPTON-85 ADSORBED IN SAID SECOND ADSORPTION BED TO SAID FIRST ADSORPTION BED UNTIL SUBSTANTIALLY ALL OF THE KRYPTON-85

Claim 3

The process according to claim 1, wherein desorpTion of each of the adsorbent beds is accomplished simultaneously with adsorption in the other bed, adsorption in each bed being terminated prior to the krypton-85 breakthrough time of the bed being adsorbed, each bed being alternately subjected to adsorption and desorption until the concentration of krypton-85 in the gas passing out of one of the beds being desorbed reaches a predetermined level, said process further comprising discharging the gas having a krypton-85 concentration of a predetermined level.

Claim 4

repeatedly transferring krypton-85 back and forth between the first bed and the second bed in said flow path by adsorbing krypton-85 in one of said adsorption beds while simultaneously desorbing krypton-85 from the other adsorption bed and thereafter desorbing krypton-85 from said one adsorption bed and adsorbing kryton-85 on said other adsorption bed,

Claim 5

repeatedly transferring krypton-85 back and forth between the first bed and the second bed in said flow path by adsorbing krypton-85 in one of said adsorption beds while simultaneously desorbing krypton-85 from the other adsorption bed and thereafter desorbing krypton-85 from said one adsorption bed and adsorbing kryton-85 on said other adsorption bed,

Claim 6

passing said exhaust gas containing krypton-85 into said flow path intermediate said first and second beds whereby substantially all of the krypton-85 in said exhaust gas is retained in said krypton-85 flow path while substantially all of the remainder of said exhaust gas is discharged through said first and second adsorption beds, and

Claim 7

passing said exhaust gas containing krypton-85 into said flow path intermediate said first and second beds whereby substantially all of the krypton-85 in said exhaust gas is retained in said krypton-85 flow path while substantially all of the remainder of said exhaust gas is discharged through said first and second adsorption beds, and

Claim 8

The process according to claim 2, wherein the gas containing krypton-85 at the predetermined level is discharged into a storing vessel.

Claim 9

A process for increasing the concentration of krypton-85 in an exhaust gas containing krypton-85 comprising:

Claim 10

A process for increasing the concentration of krypton-85 in an exhaust gas containing krypton-85 comprising:

Claim 11

withdrawing the gas in said krypton-85 flow path when the concentration of the krypton-85 and the gas therein reaches a predetermined value.

Claim 12

withdrawing the gas in said krypton-85 flow path when the concentration of the krypton-85 and the gas therein reaches a predetermined value.

Claim 13

The process according to claim 4, wherein the adsorbent beds are packed with activated carbon.

Claim 14

The process according to claim 4, wherein a portion of the gas passing out of each adsorption bed and substantially free of krypton-85 is fed to the other adsorption bed during desorption of said other adsorption bed.

Claim 15

The process of claim 4, wherein the concentration of krypton-85 is increased from on the order of 1 ppm in said exhaust gas to at least about 0.1% by volume in said desorbed gas before said desorbed gas is withdrawn.

Claim 16

The process of claim 4, wherein the krypton-85 concentration ratio of the desorbed gas to the exhaust gas is on the order of 10,000.

Claim 17

A process for separating and recovering krypton-85 contained in an exhaust gas flowing from a nuclear facility into a separating and concentrating apparatus having an inlet passage for receiving the exhaust gas, said process comprising: desorbing krypton-85 adsorbed on activated carbon packed in a first adsorption bed to obtain a desorbed gas having an increased krypton-85 concentration, communication between said first adsorption bed and said inlet passage being stopped during desorption of said first adsorption bed; introducing exhaust gas together with all of the desorbed gas produced during desorption of said first adsorption bed into a second adsorption bed packed with activated carbon, said second adsorption bed communicating with said inlet passaage during the adsorption step in said second adsorption bed, the desorption and adsorption steps in each of the adsorption beds being alternately repeated at a predetermined time interval smaller than the krypton-85 breakthrough time with respect to the activated carbon packed in each of the adsorption beds, said desorption and adsorption steps being alternately repeated without allowing the desorbed gas to flow out of the closed loop formed by the first and second adsorption beds and until the concentration of the krypton-85 in the desorbed gas reaches a preDetermined value; and charging the desorbed gas having the predetermined krypton-85 concentration to a storing tank under pressure.

Claim 18

A process for separating and recovering krypton-85 contained in an exhaust gas flowing from a nuclear facility into a separating and concentrating apparatus having an inlet passage for receiving the exhaust gas, said process comprising: desorbing krypton-85 adsorbed on activated carbon packed in a first adsorption bed to obtain a desorbed gas having an increased krypton-85 concentration, communication between said first adsorption bed and said inlet passage being stopped during desorption of said first adsorption bed; introducing exhaust gas together with all of the desorbed gas produced during desorption of said first adsorption bed into a second adsorption bed packed with activated carbon, said second adsorption bed communicating with said inlet passaage during the adsorption step in said second adsorption bed, the desorption and adsorption steps in each of the adsorption beds being alternately repeated at a predetermined time interval smaller than the krypton-85 breakthrough time with respect to the activated carbon packed in each of the adsorption beds, said desorption and adsorption steps being alternately repeated without allowing the desorbed gas to flow out of the closed loop formed by the first and second adsorption beds and until the concentration of the krypton-85 in the desorbed gas reaches a preDetermined value; and charging the desorbed gas having the predetermined krypton-85 concentration to a storing tank under pressure.

Claim 19

A process according to claim 9, wherein the adsorption bed being supplied with the exhaust gas is kept at a first temperature lower than the normal temperature and the other adsorption bed being subjected to desorption is kept at a second temperature higher than the normal temperature.

Claim 20

A process according to claim 10, wherein the first temperature is of -150*C. to 20*C. and the second temperature is of 20*C. to 200*C.

Claim 21

A process according to claim 9, wherein desorption of krypton-85 is carried out by reducing a pressure in the adsorption bed.

Claim 22

The process according to claim 9, wherein desorption is accomplished by elevating the temperature or reducing the pressure in the adsorption bed being desorbed.

Claim 23

The process according to claim 9, wherein a part of the purified exhaust gas drawn from one of the adsorption beds during adsorption is supplied to the other adsorption bed during the desorption of said other adsorption bed so as to desorb krypton-85 adsorbed on the activated carbon in said other adsorption bed.

Claim 24

A process for separating and recovering krypton-85 contained in an exhaust gas flowing from a nuclear facility into a separating and concentrating apparatus having an inlet passage for receiving the exhaust gas, said process comprising: desorbing krypton-85 absorbed on activated carbon packed in a first adsorption bed to obtain a desorbed gas comprising a carrier gas and krypton-85, said desorbed gas having an increased krypton-85 concentration, communication between said first adsorption bed and said inlet passage being stopped during desorption of said first adsorption bed; introducing exhaust gas together with all of the desorbed gas produced during desorption of said first adsorption bed into a second adsorption bed packed with activated carbon, said second adsorption bed communicating with said inlet passage during the adsorption step in said second adsorption bed, the desorption and adsorption steps in each of the adsorption beds being alternately repeated at a predetermined time interval smaller than the krypton-85 breakthrough time with respect to the activated carbon packed in each of the adsorption beds, said desorption and adsorption steps being alternately repeated without allowing the desorbed gas to flow out of the closed loop formed by the first and second adsorption beds and until the concentration of the krypton-85 in the desorbed gas reaches a first predetermined value; introducing the desorbed gas containing krypton-85 of said first predetermined value into a cryogenic distillation apparatus wherein the desorbed gas is liquified by heat exchange between the desorbed gas and a cooling mediium not in contact with the desorbed gas; selectively evaporating the carrier gas from the liquified desorbed gas thereby increasing the krypton-85 concentration in the liquified gas to a second predetermined value; and recycling the carrier gas accompanied by a small amount of krypton-85 evaporated from the cryogenic apparatus to the closed loop in oorder to further repeat adsorption and desorption of the krypton-85 in said adsorption beds.

Claim 25

A process for separating and recovering krypton-85 contained in an exhaust gas flowing from a nuclear facility into a separating and concentrating apparatus having an inlet passage for receiving the exhaust gas, said process comprising: desorbing krypton-85 absorbed on activated carbon packed in a first adsorption bed to obtain a desorbed gas comprising a carrier gas and krypton-85, said desorbed gas having an increased krypton-85 concentration, communication between said first adsorption bed and said inlet passage being stopped during desorption of said first adsorption bed; introducing exhaust gas together with all of the desorbed gas produced during desorption of said first adsorption bed into a second adsorption bed packed with activated carbon, said second adsorption bed communicating with said inlet passage during the adsorption step in said second adsorption bed, the desorption and adsorption steps in each of the adsorption beds being alternately repeated at a predetermined time interval smaller than the krypton-85 breakthrough time with respect to the activated carbon packed in each of the adsorption beds, said desorption and adsorption steps being alternately repeated without allowing the desorbed gas to flow out of the closed loop formed by the first and second adsorption beds and until the concentration of the krypton-85 in the desorbed gas reaches a first predetermined value; introducing the desorbed gas containing krypton-85 of said first predetermined value into a cryogenic distillation apparatus wherein the desorbed gas is liquified by heat exchange between the desorbed gas and a cooling mediium not in contact with the desorbed gas; selectively evaporating the carrier gas from the liquified desorbed gas thereby increasing the krypton-85 concentration in the liquified gas to a second predetermined value; and recycling the carrier gas accompanied by a small amount of krypton-85 evaporated from the cryogenic apparatus to the closed loop in oorder to further repeat adsorption and desorption of the krypton-85 in said adsorption beds.

Claim 26

A process according to claim 15, wherein the adsorption bed being supplied with the exhaust gas is kept at first temperature lower than the normal temperature and the another adsorption bed being subjected to desorption is kept at a second temperature higher than the normal temperature.

Claim 27

A process according to claim 6, wherein the first temperature is of -150*C. to 20*C. and the second temperature is of 20*C. to 200*C.

Claim 28

A process according to claim 15, wherein desorption of krypton-85 is carried out by reducing a pressure in the Adsorption bed.

Claim 29

A process according to claim 15, wherein the krypton-85 concentration in the concentrated gas is about 3 to 7 % by volume.

Claim 30

The process according to claim 15, further comprising charging the gas having a krypton-85 concentration of the second predetermined value into a storing tank under pressure.

Claim 31

The process according to claim 15, wherein desorption is accomplished by elevating the temperature or reducing the pressure of the adsorption bed being desorbed.

Claim 32

The process according to claim 15, wherein a part of the purified exhaust gas drawn from one of the adsorption beds during adsorption is supplied to the other adsorption bed during the desorption of said other adsorption bed so as to desorb krypton-85 adsorbed on the activated carbon in said other adsorption bed.

Claim 33

The process of claim 22, wherein the desorption and adsorption steps in each of the adsorption beds are alternately repeated until the krypton-85 concentration ratio of the desorbed gas to the exhaust gas is on the order of 1000.

Claim 34

A process for treating an exhaust gas from a nuclear facility to separate and concentrate krypton-85 comprising passing exhaust gas into a first adsorption bed packed with an adsorbent for krypton-85 to adsorb krypton-85 on said adsorbent, stopping the flow of exhaust gas to said first adsorption bed prior to the krypton-85 breakthrough time of the first adsorption bed, passing exhaust gas to a second adsorption bed packed with an adsorbent for krypton-85 to adsorb krypton-85 on said adsorbent, said second adsorption bed being in parallel with said first adsorption bed with respect to the incoming exhaust gas, desorbing the krypton-85 in said first adsorption bed, admixing the desorbed krypton-85 desorbed from said first adsorption bed with the incoming exhaust gas fed to said second adsorption bed, desorption of said first adsorption bed being accomplished in such a way that substantially complete desorption of the adsorbed krypton-85 occurs before the krypton-85 breakthrough time of the second adsorption bed, stopping the flow of exhaust gas to said second adsorption bed after substantially all of the krypton-85 desorbed from said first adsorption bed has been passed to said second adsorption bed and prior to the krypton-85 breakthrough time of said second adsorption bed, said second adsorption bed being desorbed under such conditions that substantially all of the krypton-85 contained therein is desorbed prior to the krypton-85 breakthrough time of said first adsorption bed, and mixing the krypton-85 desorbed from said second adsorption bed with the incoming exhaust gas passing to said first adsorption bed.

Claim 35

A process for treating an exhaust gas from a nuclear facility to separate and concentrate krypton-85 comprising passing exhaust gas into a first adsorption bed packed with an adsorbent for krypton-85 to adsorb krypton-85 on said adsorbent, stopping the flow of exhaust gas to said first adsorption bed prior to the krypton-85 breakthrough time of the first adsorption bed, passing exhaust gas to a second adsorption bed packed with an adsorbent for krypton-85 to adsorb krypton-85 on said adsorbent, said second adsorption bed being in parallel with said first adsorption bed with respect to the incoming exhaust gas, desorbing the krypton-85 in said first adsorption bed, admixing the desorbed krypton-85 desorbed from said first adsorption bed with the incoming exhaust gas fed to said second adsorption bed, desorption of said first adsorption bed being accomplished in such a way that substantially complete desorption of the adsorbed krypton-85 occurs before the krypton-85 breakthrough time of the second adsorption bed, stopping the flow of exhaust gas to said second adsorption bed after substantially all of the krypton-85 desorbed from said first adsorption bed has been passed to said second adsorption bed and prior to the krypton-85 breakthrough time of said second adsorption bed, said second adsorption bed being desorbed under such conditions that substantially all of the krypton-85 contained therein is desorbed prior to the krypton-85 breakthrough time of said first adsorption bed, and mixing the krypton-85 desorbed from said second adsorption bed with the incoming exhaust gas passing to said first adsorption bed.

Claim 36

The process according to claim 24, wherein the adsorbent in each adsorbent bed is activated carbon.

Claim 37

The process according to claim 24, wherein said first and said second adsorption beds are arranged in parallel with respect to an exhaust gas inlet for receiving exhaust gas to be treated and with respect to a purified gas outlet for discharging purified gas substantially free of krypton-85, said process further comprising passing purified gas produced during adsorption in said first adsorption bed out of said inlet and passing purified gas produced in said second adsorption bed during adsorption in said second adsorption bed being passed out of said outlet.

Claim 38

The process according to claim 26, wherein a portion of the purified gas passing out of one of the adsorption beds during adsorption in said one adsorption bed is fed to the other adsorption bed during desorption of said other adsorption bed.

Claim 39

The process according to claim 26, further including withdrawing all of the desorbed gas passing out of one of said beds during desorption when the concentration of krypton-85 in said desorbed gas reaches a predetermined value.