CRD Tech Specs

Question 1

What is 3.1.4 Control Rod Alignment?

Answer 1

3.1.4 Control Rod Alignment

All control rods, including their position indication channels, shall be OPERABLE and aligned to within 8 inches of all other rods in their respective group, and the control rod position deviation alarm shall be OPERABLE.

APPLICABILITY: MODES 1 and 2.

Question 2

3.1.4 Control Rod Alignment Actions

Answer 2

3.1.4 Control Rod Alignment Actions < 1 hour

A. One channel of rod position indication inoperable for one or more control rods.

• Perform SR 3.1.4.1 (rod position verification).
• Once within 15 minutes following any rod motion in that group

B. Rod position deviation alarm inoperable

• Perform SR 3.1.4.1 (rod position verification).
• Once within 15 minutes following any rod motion in that group

Question 3

What is the basis of T.S. 3.1.4 CR Align?

Answer 3

CR Alignment Basis

Maximum control rod misalignment is an initial assumption in the safety analysis that directly affects core power distributions and assumptions of available SDM.

Question 4

What are the CR Misalignment Repercussions?

Answer 4

CR Misalignment Repercussions

May cause increased power peaking, due to the asymmetric reactivity distribution

Reduction in the total available control rod worth for reactor shutdown.

Failure to meet the requirements of this LCO (3.1.4) may produce unacceptable
power peaking factors and LHRs, or unacceptable SDM, any of which
may constitute initial conditions inconsistent with the safety analysis

Question 5

What provides the Immediate Shutdown reactivity worth?

Answer 5

Immediate Shutdown Reactivity Worth

shutdown and regulating rods

Question 6

What is the implication of a Stuck Rod during movement of a rod group?

Answer 6

Stuck Rod during Group Movement

May cause excessive power peaking

Discussed in Safety Analysis

Question 7

What is the implication of a plant trip and Stuck Rod?

Answer 7

Trip and Stuck Rod

Requires an evaluation to determine that sufficient reactivity worth is held in the remaining control rods to meet the SDM requirement with the maximum worth rod stuck fully withdrawn.

If a control rod is stuck in the fully withdrawn position, its worth is added
to the SDM requirement, since the safety analysis does not take two
stuck rods into account.

Question 8

What is the implication of a Dropped Rod?

Answer 8

Dropped Rod

• Causes an initial power reduction followed by a return towards the original power, due to positive reactivity feedback from the negative moderator temperature coefficient.
• Increased peaking during the power increase may result in excessive local Linear Heat Rates (LHRs).

Question 9

When is a Part Length Rod Operable?

Answer 9

Part Length Rod Operable

The OPERABILITY requirement for the part-length rods is that they are fully withdrawn

Question 10

What genrates the 8 Inch Deviation Alarm?

Answer 10

8 Inch Deviation Alarm

PIP or SPI

Either must be operable

Question 11

When is PIP Operable?

Answer 11

PIP Operable

• If the digital position readout or the PPC display provides valid rod position indication,

OR

• If the cam operated red matrix light (regulating and part-length rods only) gives positive (ON) indication of rod position.

Question 12

When is SPI Operable?

Answer 12

SPI Operable

• If the magnetically operated reed switches are providing valid indication of rod position either via the plant process computer

OR

• By taking direct readings of the output from the magnetic reed switches

OR

• If the reed switch operated red matrix light (shutdown rods only) gives positive (ON)

indication of rod position.

Question 13

What is the Intent of Actions in LCO 3.1.4, 3.1.5 and 3.1.6?

Answer 13

Intent of Actions in LCO 3.1.4, 3.1.5 and 3.1.6

1. There is adequate SDM available in withdrawn control rods to assure the reactor is shutdown by, and remains shutdown following, a reactor trip,
2. The control rod positioning does not cause unacceptable axial or radial flux peaking, and,
3. The programmed rod withdrawal sequence and group overlap result in reactivity insertion rates within the assumptions of the Inadvertent Control Rod Bank Withdrawal Analyses.

Question 14

What happens if more than 1 rod is out of position and not movable?

Answer 14

More than 1 Rod out of Position

The analyses account for operation with one (and only one) mispositioned rod (a dropped rod being the limiting case). With more than one mispositioned rod, the plant would be outside the bounds of the analyses and must be shutdown.

Question 15

What happens if a Part-Length Rod is inserted beyond the limit and not movable?

Answer 15

Part-Length Rod Insertion

If one or more part length rods are inserted beyond the limit, Condition
3.1.5 A is entered; the rods are declared inoperable and Condition 3.1.4 E
is entered (and 3.1.4 C if it is misaligned). Condition 3.1.4 D is not
applicable to part-length rods since it only addresses full-length rods.

Question 16

Why is Radial Peaking Verification required if one control rod is misaligned by > 8 inches and continued power operations is desired or you have to reduce to less than 75% RTP?

Answer 16

Radial Peaking Verification

Xenon redistribution in the core starts to occur as soon as a rod becomes
misaligned.

• Verifying peaking is one way to monitor distribution.
• Reducing THERMAL POWER to ≤ 75% RTP ensures acceptable power distributions are maintained.

Question 17

Why 2 hours to verify peaking factors if a rod is >8 inches missaligned?

Answer 17

2-hour verification

2-hour time period is sufficient to:

• Identify cause of a misaligned rod;
• Take appropriate corrective action to realign the rods; and
• Minimize the effects of xenon redistribution.

Question 18

More than one control rod inoperable?

Answer 18

If more than one control rod, whether full length or part length,
are inoperable for any reasons, then shutdown.

Question 19

What is 3.1.5 Shutdown and Part-Length Control Rod Group Insertion Limits?

Answer 19

3.1.5 Shutdown and Part-Length Control Rod Group Insertion Limits

All shutdown and part-length rod groups shall be withdrawn to ≥ 128 inches.

Mode 1

and

Mode 2 with any regulating rod withdrawn above 5 inches

Question 20

What are the 3.1.5 Shutdown and Part-Length Control Rod Group Insertion Limits <1hour actions?

Answer 20

3.1.5 Shutdown and Part-Length Control Rod Group Insertion Limits

<1 hour actions

One or more shutdown or part-length rods not within limit. (withdrawn to ≥ 128 inches in Mode 1 or Mode 2 with a reg rod > 5 inches)

Immediately

Declare affected control rod(s) inoperable and enter the applicable Conditions and Required Actions of LCO 3.1.4.

Question 21

Why are Shutdown Rods fully withdrawn prior to critical?

Answer 21

Shutdown Rods Fully Withdrawn

Fully withdrawn at 128 inches - negligible region of integral rod worth

Ensures

• The minimum SDM is maintained; and
• The potential effects of a control rod ejection accident are limited to acceptable limits

Question 22

What is 3.1.6 Regulating Rod Group Position Limits?

Answer 22

3.1.6 Regulating Rod Group Position Limits

The Power Dependent Insertion Limit (PDIL) alarm circuit and the Control Rod Out Of Sequence (CROOS) alarm circuit shall be OPERABLE, and the regulating rod groups shall be limited to the withdrawal sequence, overlap, and insertion limits specified in the COLR.

Mode 1 and 2

Question 23

What are the 3.1.6 Regulating Rod Group Position Limits one hour or less actions?

Answer 23

3.1.6 Regulating Rod Group Position Limits

One Hour or Less Actions

• PDIL or CROOS alarm circuit inoperable.
  
  • Perform SR 3.1.6.1 (group position verification).
  • Once within 15 minutes following any rod motion