Containment Hydrogen

Question 1

What are the sources of hydrogen generation in containment?

Answer 1

• zirc-hydriding of fuel cladding under high temperature in water
• corrosion of containment zinc and aluminum due to containment spray and high temperatures
• hydrogen coming out of solution in the PCS
• radiolytic decomposition of water (gamma)

Question 2

What is the purpose of the hydrogen analyzers?

Answer 2

Provide continuous monitoring in post accident situation

Question 3

Where can hydrogen sampling be done from?

Answer 3

Control Room

Question 4

What is the function of local hydrogen analyzer panels C-161/162?

Answer 4

Calibration

Question 5

How is the hydrogen analyzing system normally maintained?

Answer 5

Normally in STANDBY

Question 6

Why is the hydrogen analyzing system normally maintained in STANDBY?

Answer 6

When in STANDBY, both local and remote panels are powered up, and heaters are energized. This permits rapid system startup, because the system takes approximately 6 hours to warm up upon energizing.

Question 7

Which channel of hydrogen monitoring is preferred to be in service, and why?

Answer 7

Left channel, because it is the only channel that provides input into the Emergency Response Data Link System.

Question 8

What happens to the hydrogen monitoring system on CHP/CHR?

Answer 8

• Hydrogen sample isolation valves go closed.

- Valves can be re-opened if keyswitch is placed in the ACCIDENT position

Question 9

What is a precaution for the hydrogen monitoring system if CHP or CHR actuates?

Answer 9

If pump is in ANALYZE position, pump will run without a flow path (isolation valves close on CHP/CHR) and damage to the pump will occur.

Question 10

What are the consequences of having a hydrogen burn inside containment following a LOCA?

Answer 10

Could endanger the integrity of the containment structure, endangering the health and safety of the public

Question 11

What is the consequence of vapor binding the PCPs?

Answer 11

Loss of ability to restore forced circulation

Question 12

What are the indications of vapor bound pumps?

Answer 12

• When the pump is running, it will have low or fluctuating pump amps and low discharge pressure.
• When starting the pump, it will have unusually low starting amps, and low discharge pressure.

Question 13

What is the largest contributor of dissolved hydrogen in the PCS during normal power operations?

Answer 13

Hydrogen added to the VCT for oxygen scavenging

Question 14

What was the largest contributor to hydrogen in containment during the TMI event?

Answer 14

Zirc/water reaction

Question 15

What is the concern of moisture presence in the hydrogen monitoring sample stream?

Answer 15

Could damage the analyzer and the sample pump

Question 16

What is overload protection?

Answer 16

Protects motor windings and all other components in the electrical flow path from damage due to excessive current.

Question 17

Why is hydrogen sampling only performed from the remote panels?

Answer 17

System isolation valves can’t be operated from the local panels, only the remote (control room) panels

Question 18

Why does EOP 4 direct you to de-energize MCC-9?

Answer 18

Removes power from non-vital equipment in containment to reduce the possibility of an electrical spark that could ignite hydrogen.