40EP-9EO04 Steam Generator Tube Rupture (SGTR)

Question 1

What are the major Mitigating Strategy steps for 40EP-9EO04 Steam Generator Tube Rupture (SGTR)?

Answer 1

• Regain RCS inventory control and CTMTN isol.
• Cool RCS using BOTH SG’s to Th < 540°F (prevents lifting SG safeties)
• Identify and isolate affected SG
• De-pressurize RCS to < 1135 and ±50 psi of SG
• Maintain affected SG 45-80% NR
• C/D RCS with good SG
• Place SDC in svc

Question 2

During a SGTR with LOOP and Stuck open ADV, how long do you have to cover affected SG tubes?

Answer 2

• 46 minutes TCA
• Use 2 AFW pumps
• scrubs Iodine, protects the public

Question 3

What kind of detectors are the RU monitors for the main steam lines? 139/140, 142 a/b/c/d and what limitation is there associated with this type of detector

Answer 3

• N16 detectors

- Proportional to Rx power, lower initial power harder to detect

Question 4

What is the accuracy of RU-139/140 Main steam line detectors (MSSS)

Answer 4

• 10-15 gpm

Question 5

What is the accuracy of the main steam line detectors 142 a/b/c/d (Turb 140’)

Answer 5

• 30 gpd

Question 6

What action is required if Main steam line RU monitors 139/140 (MSSS) or SGBD RU-4/5 alarm in HIGH

Answer 6

• Isolate Blowdown

Question 7

How do you know if a SG leak is high or low in the tube bundle?

Answer 7

• High tube leak indicated in steam line RU’s

- Low tube leaks indicated in SGBD RU’s

Question 8

For the Condenser PFB RU-141 a/b, what is the accuracy of each channel, which channel actuates PFB?

Answer 8

A - Actuates 1 gpm

B - Better 50 gpd

Question 9

During a SGTR, what actions are taken to help reduce release to offsite prior to the cooldown?

Answer 9

• Ensure AR PFU in “Thru Filter Mode”

- SBCV’s 1007/8 to OFF

Question 10

During a SGTR what is the initial cooldown target and why?

Answer 10

• Th < 540°F

- Prevents lifting SG MSSV’s when isolated

Question 11

During a SGTR what is the preferred method of cooldown and alternate cooldown methods?

Answer 11

• SBCV’s 1001-1006
• ADV’s from CR
• SBCV’s 1007/8
• ADV’s locally

Question 12

While depressurizing the RCS during a SGTR, if spray is not available or cannot maintain pressure in band, what else can be done to lower pressure?

Answer 12

• Use RCGVS

Question 13

During a SGTR, how do you maintain the isolated SG < 1135 psia?

Answer 13

• RCS Cooldown
• MSIV bypass (monitored)
• ADV’s (unmonitored)

Question 14

During a SGTR, what do you do if the wrong SG was isolated?

Answer 14

• Restore SG
• Then Isolate affected SG
• Maintain heat removal capability

Question 15

What is HPSI Throttle Criteria?

Answer 15

• ≥ 24°F Subcooling
• > 10% Lpzr ↔ or ↑
• Un-isolated SG 45-60% NR with feed
• RVUH ≥ 16%

Question 16

At what pressure would you stop the LPSI pumps and close their injection vlvs?

Answer 16

• Ppzr > 220 psia

- pressure is controlled

Question 17

During a SGTR what are the RCS CDR’s?

Answer 17

< 100°F/hr with RCP’s
< 30°F/hr on Natural Circ.
- prevents loop from becoming stagnant due to asymmetric C/D

Question 18

During a SGTR when and how often does Chemistry have to perform RCS Boron samples

Answer 18

• Prcs < Psg

- Every 30 Minutes

Question 19

During a SGTR what must be done, in regards to RCP’s, what must be done if all RCP’s have been stopped?

Answer 19

• Disable RCP brkrs for isolated SG

- Prevents inadvertent dilution

Question 20

During a SGTR what level do you maintain the isolated SG?

Answer 20

• 45 - 80% NR

Question 21

During a SGTR how do you maintain the isolated SG level?

Answer 21

• Backflow to RCS (preferred)
• Drain to condenser (SGBD)
• Steaming thru MSIV bypass
• Increase RCS press to raise level

Question 22

Which SG LT’s are less sensitive to temperature de-calibration?

Answer 22

• NR LT’s

Question 23

During a SGTR, what must be done before restarting a RCP and why?

Answer 23

• RCS Sample

- Check for unborated water slug due to backflow

Question 24

What parameters are used to verify Natural Circulation?

Answer 24

• Loop ▲T < 65°F
• Tc and Th ↔ or ↓
• ≥ 24°F Subcooled via CET
• < 30°F ▲T B/W Th and max quadrant CET

Question 25

What is loop transit time while in Natural Circulation?

Answer 25

• 5-15 Minutes

Question 26

During SGTR, what is required to use Backflow during SG C/D?

Answer 26

• RCP’s operating

- LD in svc

Question 27

During a SGTR what methods are available to C/D and depressurize the SG?

Answer 27

• Backflow (preferred)
• Steam with SBCS
• Drain to condenser (feed & bleed)
• Ambient cooling

Question 28

What are SDC Entry requirements?

Answer 28

• Lpzr > 30% and controlled
• ≥ 24°F RCS Subcooling
• Ppzr < 385 psia
• Th < 335°F
• RCS activity wont result in unacceptable doses outside CTNMT