Patent Number: 
Section: claims

1. A radiation monitor comprising:a shutter installed between a check radiation source and a radiation detector;a calculation section which calculates a radiation dose from a detection signal outputted by said radiation detector;an AC solenoid to be operated by an AC power source;a temperature switch which is attached to said AC solenoid and whose contact is reversed from an opened state to a closed state when temperature thereof is equal to or more than a set value;a circuit protector which has a contact and is connected in series to said AC solenoid; anda mode selection switch connected in series to said AC solenoid,wherein said shutter is maintained in a closed state when said mode selection switch is set to a normal mode;said mode selection switch is changed from the normal mode to a check radiation source mode, thereby flowing an AC current through said AC solenoid to change said shutter from the closed state to an opened state; andthe contact of said temperature switch is reversed from the opened state to the closed state, thereby disconnecting the contact of said circuit protector to interrupt the AC current that flows through said AC solenoid. 2. The radiation monitor according to claim 1,further comprising a relay which has a first contact and a second contact and is disposed in series to said temperature switch,the first contact being connected in parallel to said temperature switch, andthe second contact being connected in series to said AC solenoid. 3. The radiation monitor according to claim 1,wherein said calculation section calculates a net value deviation of said check radiation source when setting of said mode selection switch is changed from the normal mode to the check radiation source mode. 4. The radiation monitor according to claim 3,wherein said calculation section determines that said check radiation source is normal if the calculated net value deviation is kept within an acceptable range, and determines that said check radiation source is abnormal if the calculated net value deviation is out of the acceptable range. 5. A radiation monitor comprising:a check radiation source which moves between a facing position and a shield position;a radiation detector which outputs a detection signal when radiation is made incident;a calculation section which calculates a radiation dose from the detection signal outputted by said radiation detector;an AC solenoid to be operated by an AC power source;a temperature switch which is attached to said AC solenoid and whose contact is reversed from an opened state to a closed state when temperature thereof is equal to or more than a set value;a circuit protector which has a contact and is connected in series to said AC solenoid; anda mode selection switch connected in series to said AC solenoid,wherein said check radiation source is maintained at the shield position when said mode selection switch is set to a normal mode;said mode selection switch is changed from the normal mode to a check radiation source mode, thereby flowing an AC current through said AC solenoid to move said check radiation source from the shield position to the facing position; andthe contact of said temperature switch is reversed from the opened state to the closed state, thereby disconnecting the contact of said circuit protector to interrupt the AC current that flows through said AC solenoid. 6. The radiation monitor according to claim 5,further comprising a relay which has a first contact and a second contact and is disposed in series to said temperature switch,the first contact being connected in parallel to said temperature switch, andthe second contact being connected in series to said AC solenoid. 7. The radiation monitor according to claim 5,wherein said calculation section calculates a net value deviation of said check radiation source when setting of said mode selection switch is changed from the normal mode to the check radiation source mode. 8. The radiation monitor according to claim 7,wherein said calculation section determines that said check radiation source is normal if the calculated net value deviation is kept within an acceptable range, and determines that said check radiation source is abnormal if the calculated net value deviation is out of the acceptable range. 9. A radiation monitor comprising:a shutter installed between a check radiation source and a radiation detector;a calculation section which calculates a radiation dose from a detection signal outputted by said radiation detector;an AC solenoid to be operated by an AC power source;a temperature switch which is attached to said AC solenoid and whose contact is reversed from an opened state to a closed state when temperature thereof is equal to or more than a set value;a fuse connected in series to said AC solenoid; anda mode selection switch connected in series to said AC solenoid,wherein said shutter is maintained in a closed state when said mode selection switch is set to a normal mode;said mode selection switch is changed from the normal mode to a check radiation source mode, thereby flowing an AC current through said AC solenoid to change said shutter from the closed state to an opened state; andthe contact of said temperature switch is reversed from the opened state to the closed state, thereby fusing said fuse to interrupt the AC current that flows through said AC solenoid. 10. The radiation monitor according to claim 9,further comprising a relay which has a first contact and a second contact and is disposed in series to said temperature switch,the first contact being connected in parallel to said temperature switch, andthe second contact being connected in series to said AC solenoid. 11. The radiation monitor according to claim 9,wherein said calculation section calculates a net value deviation of said check radiation source when setting of said mode selection switch is changed from the normal mode to the check radiation source mode. 12. The radiation monitor according to claim 11,wherein said calculation section determines that said check radiation source is normal if the calculated net value deviation is kept within an acceptable range, and determines that said check radiation source is abnormal if the calculated net value deviation is out of the acceptable range.