ML22240A028
| ML22240A028 | |
| Person / Time | |
|---|---|
| Issue date: | 06/02/2015 |
| From: | NRC/NRR/DSS/STSB |
| To: | |
| Craig Harbuck NRR/DSS 301-415-3140 | |
| Shared Package | |
| ML22240A001 | List:
|
| References | |
| Download: ML22240A028 (33) | |
Text
GTST AP1000- B17-3.1.7, Rev. 1
Advanced Passive 1000 (AP1000)
Generic Technical Specification Traveler (GTST)
Title:
Changes related to Section 3.1.7, Rod Position Indication
I. Technical Specifications Task Force (TSTF) Travelers, Approved Since Revision 2 of STS NUREG-1431, and Used to Develop this GTST
TSTF Number and
Title:
TSTF-425, Rev. 3, Relocate Surveillance Frequencies to Licensee Control - RITSTF Initiative 5b TSTF-437-T, Rev. 1, Correction of Rod Position Indication Condition
TSTF-425: NUREG-1430, -1431, -1432, -1433, -1434 TSTF-437: NUREG-1431
NRC Approval Date:
TSTF-425: 18-Mar-2009 TSTF-437: NA
TSTF Classification:
TSTF-425: Technical change TSTF-437: Editorial Change
Date report generated:
Tuesday, June 02, 2015 Page 1 GTST AP1000- B17-3.1.7, Rev. 1
II. Reference Combined License (RCOL) Standard Departures (Std. Dep.), RCOL COL Items, and RCOL Plant-Specific Technical Specifications (PTS) Changes Used to Develop this GTST
RCOL Std. Dep. Number and
Title:
None
RCOL COL Item Number and
Title:
None
RCOL PTS Change Number and
Title:
VEGP LAR DOC A014: SR 3.1.7.1 Frequency is revised to add once as the lead in.
Date report generated:
Tuesday, June 02, 2015 Page 2 GTST AP1000- B17-3.1.7, Rev. 1
III. Comments on Relations Among TSTFs, RCOL Std. Dep., RCOL COL Items, and RCOL PTS Changes
This section discusses the considered changes that are: (1) applicable to operating reactor designs, but not to the AP1000 design; (2) already incorporated in the GTS; or (3) superseded by another change.
TSTF-425 is deferred for future consideration.
TSTF-437 was drafted against NUREG-1431, Revision 2. However, it was not adopted by the NRC in NUREG-1431 Revision 3 or Revision 4. Since then, TSTF-547 is drafted and under NRC review and makes different changes from that in TSTF-437. This change also does not currently exist for AP1000 plants. Since neithe r issued COL TS for VEGP or V.C. Summer include this option, and since each represented AP1000 Utility is committed to maintaining standardizat ion, there currently is no basis f or an AP1000 STS that differs from the GTS and the issued COLs. It is appropriate f or the AP1000 NUREG to remain consistent with the GTS (and issued COLs) until TSTF-547 is dispositioned. At that time, a subsequent GTST can be considered f or the AP1000 NUREG.
Date report generated:
Tuesday, June 02, 2015 Page 3 GTST AP1000- B17-3.1.7, Rev. 1
IV. Additional Changes Proposed as Part of this GTST (modifications proposed by NRC staff and/or clear editorial changes or deviations identified by preparer of GTST)
APOG Recommended Changes to Improve the Bases
Throughout the Bases, references to Sections and Chapters of the FSAR do not include the FSAR clarifier. Since these Section and Chapter references are to an external document, it is appropriate to include the FSAR modifier. (DOC A003)
Date report generated:
Tuesday, June 02, 2015 Page 4 GTST AP1000- B17-3.1.7, Rev. 1
V. Applicability
Affected Generic Technical Specifications and Bases:
Section 3.1.7, Rod Position Indication
Changes to the Generic Technical Specifications and Bases:
SR 3.1.7.1 Frequency is revised to add once as a lead in. (DOC A014)
The acronym FSAR is added to modify Section and Chapter in references to the FSAR throughout the Bases. (DOC A003)
Date report generated:
Tuesday, June 02, 2015 Page 5 GTST AP1000- B17-3.1.7, Rev. 1
VI. Traveler Information
Description of TSTF changes:
NA
Rationale for TSTF changes:
NA
Description of changes in RCOL Std. Dep., RCOL COL Item(s), and RCOL PTS Changes:
SR 3.1.7.1 Frequency is revised to add once as the lead in. The revised Frequency states Once prior to criticality after each removal of reactor head.
Rationale for changes in RCOL Std. Dep., RCOL COL Item(s), and RCOL PTS Changes:
As described in the STS Writers Guide, the frequency of performance is always implied as once per unless otherwise stated. The frequency for SR 3.1.7.1 is vague in not explicitly stating once. TS Section 1.4, Frequency, Example 1.4-2 describes that The use of Once indicates a single performance will satisfy the specified Frequency.
Since SR 3.1.7.1 does not include the clarifier once, a potential misreading of the frequency could lead to performance prior to each criticality after removal of the reactor head. This change provides clarification and will avoid confusion.
Description of additional changes proposed by NRC staff/preparer of GTST:
The acronym FSAR is added to modify Section and Chapter in references to the FSAR throughout the Bases. (DOC A003)
Rationale for additional changes proposed by NRC staff/preparer of GTST:
Since Bases references to FSAR Sections and Chapters are to an external document, it is appropriate to include the FSAR modifier.
Date report generated:
Tuesday, June 02, 2015 Page 6 GTST AP1000- B17-3.1.7, Rev. 1
VII. GTST Safety Evaluation
Technical Analysis:
Addition of once as lead in in SR 3.1.7.1 Frequency
Adding once as a lead in in the Frequency will clarify that single performance of the surveillance will satisfy the requirement. It will avoid any potential misreading that the surveillance needs to be performed prior to each criticality after removal of the reactor vessel head. This change will add appropriate clarification and is acceptable for AP1000 STS.
Remaining Changes
The remaining changes are editorial, clarifying, grammatical, or otherwise considered administrative. These changes do not affect the technical content, but improve the readability, implementation, and understanding of the requirements, and are therefore acceptable.
Having found that this GTSTs proposed changes to the GTS and Bases are acceptable, the NRC staff concludes that AP1000 STS Subsection 3.1.7 is an acceptable model Specification for the AP1000 standard reactor design.
References to Previous NRC Safety Evaluation Reports (SERs):
None
Date report generated:
Tuesday, June 02, 2015 Page 7 GTST AP1000- B17-3.1.7, Rev. 1
VIII. Review Information
Evaluator Comments:
None
Pranab K. Samanta Brookhaven National Laboratory (631) 344-4948 samanta@bnl.gov
Review Information:
Availability for public review and comment on Revision 0 of this traveler approved by NRC staff on 4/1/2014.
APOG Comments (Ref. 7) and Resolutions
(Internal #3) Throughout the Bases, references to Sections and Chapters of the FSAR do not include the FSAR modifier. Since these Section and Chapter references are to an external document, it is appropriate to include the FSAR modifier. This is resolved by adding the FSAR modifier as appropriate.
(Internal #15) Remove TSTF-437 changes from GTST, since no AP1000 COL plant-specific TS include it, and because it is superseded by TSTF-547, which is currently under NRC/NRR/STSB review. TSTF-437 is listed in the reference disposition tables as TSTF deferred f or future consideration.
(Internal #84) 3.1.07, Pg. 25, Required Action B.4 Completion Time was changed to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, consistent with AP1000 GTS.
NRC Final Approval Date: 6/02/ 2015
NRC
Contact:
T. R. Tjader United States Nuclear Regulatory Commission 301-415-1187 Theodore.Tjader@nrc.gov
Date report generated:
Tuesday, June 02, 2015 Page 8 GTST AP1000- B17-3.1.7, Rev. 1
IX. Evaluator Comments for Consideration in Finalizing Technical Specifications and Bases
None
Date report generated:
Tuesday, June 02, 2015 Page 9 GTST AP1000- B17-3.1.7, Rev. 1
X. References Used in GTST
- 1. AP1000 DCD, Revision 19, Section 16, Technical Specifications, June 2011 (ML11171A500).
- 2. Southern Nuclear Operating Company, Vogtle Electric Generating Plant, Unit 3 and 4, Technical Specifications Upgrade License Amendment Request, February 24, 2011 (ML12065A057).
- 3. RAI Letter No. 01 Related to License Amendment Request (LAR) 12- 002 for the Vogtle Electric Generating Plant Units 3 and 4 Combined Licenses, September 7, 2012 (ML12251A355).
- 4. Southern Nuclear Operating Company, Vogtle Electric Generating Plant, Units 3 and 4, Response to Request for Additional Information Letter No. 01 Related to License Amendment Request LAR 002, ND 2015, October 04, 2012 (ML12286A363 and ML12286A360).
- 5. NRC Safety Evaluation (SE) for Amendment No. 13 to Combined License (COL) No. NPF-91 for Vogtle Electric Generating Plant (VEGP) Unit 3, and Amendment No. 13 to COL No.
NPF-92 for VEGP Unit 4, September 9, 2013 (ADAMS Package Accession No. ML13238A337), which contains:
ML13238A355, Cover Letter - Issuance of License Amendment No. 13 for Vogtle Units 3 and 4 (LAR 12-002).
ML13238A359, Enclosure 1 - Amendment No. 13 to COL No. NPF-91 ML13239A256, Enclosure 2 - Amendment No. 13 to COL No. NPF-92 ML13239A284, Enclosure 3 - Revised plant-specific TS pages (Attachment to Amendment No. 13)
ML13239A287, Enclosure 4 - Safety Evaluation (SE), and Attachment 1 - Acronyms ML13239A288, SE Attachment 2 - Table A - Administrative Changes ML13239A319, SE Attachment 3 - Table M - More Restrictive Changes ML13239A333, SE Attachment 4 - Table R - Relocated Specifications ML13239A331, SE Attachment 5 - Table D - Detail Removed Changes ML13239A316, SE Attachment 6 - Table L - Less Restrictive Changes
The following documents were subsequently issued to correct an administrative error in Enclosure 3:
ML13277A616, Letter - Correction To The Attachment (Replacement Pages) - Vogtle Electric Generating Plant Units 3 and 4-Issuance of Amendment Re:
Technical Specifications Upgrade (LAR 12- 002) (TAC No. RP9402)
ML13277A637, Enclosure 3 - Revised plant-specific TS pages (Attachment to Amendment No. 13) (corrected)
- 6. TSTF-GG-05-01, W riter's Guide for Plant-Specific Improved Technical Specifications, June 2005.
Date report generated:
Tuesday, June 02, 2015 Page 10 GTST AP1000- B17-3.1.7, Rev. 1
- 7. APOG-2014- 008, APOG (AP1000 Utilities) Comments on AP1000 Standardized Technical Specifications (STS) Generic Technical Specification Travelers (GTSTs), Docket ID NRC-2014- 0147, September 22, 2014 (ML14265A493).
Date report generated:
Tuesday, June 02, 2015 Page 11 GTST AP1000- B17-3.1.7, Rev. 1
XI. MARKUP of the Applicable GTS Subsection for Preparation of the STS NUREG
The entire section of the Specifications and the Bases associated with this GTST is presented next.
Changes to the Specifications and Bases are denoted as follows: Deleted portions are marked in strikethrough red font, and inserted portions in bold blue f ont.
Date report generated:
Tuesday, June 02, 2015 Page 12 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
3.1 REACTIVITY CONTROL SYSTEMS
3.1.7 Rod Position Indication
LCO 3.1.7 The Digital Rod Position Indication (DRPI) System and the Bank Demand Position Indication System shall be OPERABLE.
APPLICABILITY: MODES 1 and 2.
ACTIONS
NOTE -----------------------------------------------------------
Separate Condition entry is allowed for each inoperable rod position indicator and each demand position indicator.
CONDITION REQUIRED ACTION COMPLETION TIME
A. One DRPI per group A.1 Verify the position of the Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> inoperable for one or rods with inoperable more groups. position indicators by using the On-line Power Distribution Monitoring System (OPDMS).
A.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
B. More than one DRPI per B.1 Place the control rods Immediately group inoperable. under manual control.
AND
B.2 Monitor and record Reactor Once per 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Coolant System (RCS) Tavg.
AND
AP1000 STS 3.1.7-1 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 13 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME
B. (continued) B.3 Verify the position of the Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> rods with inoperable position indicators indirectly by using the incore detectors.
AND
B.4 Restore inoperable position 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> indicators to OPERABLE status such that a maximum of one DRPI per group is inoperable.
C. One or more rods with C.1 Verify the position of the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> inoperable position rods with inoperable indicators have been position indicators by using moved in excess of the OPDMS.
24 steps in one direction since the last OR determination of the rod s position. C.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
D. One demand position D.1.1 Verify by administrative Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> indicator per bank means all DRPIs for the inoperable for one or affected banks are more banks. OPERABLE.
AND
D.1.2 Verify the most withdrawn Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> rod and the least withdrawn rod of the affected banks are 12 steps apart.
AP1000 STS 3.1.7-2 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 14 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME
D. (continued) D.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
E. Required Action and E.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met.
SURVEILLANCE REQUIREMENTS
SURVEILLANCE FREQUENCY
SR 3.1.7.1 Verify each DRPI agrees within 12 steps of the group Once Pprior to demand position for the full indicated range of rod criticality after travel. each removal of the reactor head
AP1000 STS 3.1.7-3 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 15 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
B 3.1 REACTIVITY CONTROL SYSTEMS
B 3.1.7 Rod Position Indication
BASES
BACKGROUND According to GDC 13 (Ref. 1), instrumentation to monitor variables and systems over their operating ranges during normal operation, anticipated operational occurrences (AOOs), and accident conditions must be OPERABLE. LCO 3.1.7 is required to ensure OPERABILITY of the control rod position indicators to determine control rod positions and thereby ensure compliance with the control rod alignment and insertion limits.
The OPERABILITY, including position indication, of the shutdown and control rods is an initial assumption in the safety analyses that assume rod insertion upon reactor trip. Maximum rod misalignment is an initial assumption in the rod cluster control assembly (RCCA) misalignment safety analysis that directly affects core power distributions and assumptions of available SDM. Rod position indication is required to assess OPERABILITY and misalignment.
Mechanical or electrical failures may cause a control rod to become inoperable or to become misaligned from its group. Control rod inoperability or misalignment may cause increased power peaking due to the asymmetric reactivity distribution and a reduction in the total available rod worth for reactor shutdown. Therefore, control rod alignment and OPERABILITY are related to core operation in design power peaking limits and the core design requirement of a minimum SDM.
Limits on control rod alignment and OPERABILITY have been established, and rod positions are monitored and controlled during power operation to ensure that the power distribution and reactivity limits defined by the design power peaking and SDM limits are preserved.
RCCAs, or rods, are moved out of the core (up or withdrawn) or into the core (down or inserted) by their control rod drive mechanisms. The RCCAs are divided among control banks and shutdown banks. Each bank may be further subdivided into two groups to provide for precise reactivity control.
The axial position of shutdown rods and control rods are determined by two separate and independent systems: the Bank Demand Position Indication System (commonly called group step counters) and the Digital Rod Position Indication (DRPI) System.
AP1000 STS B 3.1.7-1 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 16 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
BACKGROUND (continued)
The Bank Demand Position Indication System counts the pulses from the Rod Control System that move the rods. There is one step counter for each group of rods. Individual rods in a group receive the same signal to move and should, therefore, be at the same position indicated by the group step counter for that group. The Bank Demand Position Indication System is considered highly precise (+/- 1 step or +/- 5/8 inch). If a rod does not move one step for each demand pulse, the step counter will still count the pulse and incorrectly reflect the position of the rod.
The DRPI System provides a highly accurate indication of actual control rod position, at a lower precision than the step counters. This system is based on inductive analog signals from a series of coils spaced along a hollow tube with a center to center distance of 3.75 inches, which is 6 steps. To increase the reliability of the system, the inductive coils are connected alternately to data system A or B. Thus, if one system fails, the DRPI will function at half accuracy with an effective coil spacing of 7.5 inches, which is 12 steps. Therefore, the normal indication accuracy of the DRPI System is +/- 6 steps (+/- 3.75 inches), and the maximum uncertainty is +/- 12 steps (+/- 7.5 inches). W ith an indicated deviation of 12 steps between the group step counter and DRPI, the maximum deviation between actual rod position and the demand position could be 24 steps, or 15 inches.
APPLICABLE Control and shutdown rod position accuracy is essential during power SAFETY operation. Power peaking, ejected rod worth, or SDM limits may be ANALYSES violated in the event of a Design Basis Accident (Ref. 2), with control or shutdown rods operating outside their limits undetected. Therefore, the acceptance criteria for rod position indication is that rod positions must be known with sufficient accuracy in order to verify the core is operating within the group sequence, overlap, design peaking limits, ejected rod worth, and with minimum SDM (LCO 3.1.5, Shutdown Bank Insertion Limits, LCO 3.1.6, Control Bank Insertion Limits ). The rod positions must also be known in order to verify the alignment limits are preserved (LCO 3.1.4, Rod Group Alignment Limits ). Control rod positions are continuously monitored to provide operators with information that assures the plant is operating within the bounds of the accident analysis assumptions.
The control rod position indicator channels satisfy Criterion 2 of 10 CFR 50.36(c)(2)(ii). The control rod position indicators monitor control rod position, which is an initial condition of the accident.
AP1000 STS B 3.1.7-2 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 17 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
LCO LCO 3.1.7 specifies that one DRPI System and one Bank Demand Position Indication System be OPERABLE for each control rod. For the control rod position indicators to be OPERABLE requires meeting the SR of the LCO and the following:
- a. The DRPI System indicates within 12 steps of the group step counter demand position as required by LCO 3.1.4, Rod Group Alignment Limits ;
- b. For the DRPI System there are no failed coils; and
- c. The Bank Demand Indication System has been calibrated either in the fully inserted position or to the DRPI System.
The 12 step agreement limit between the Bank Demand Position Indication System and the DRPI System indicates that the Bank Demand Position Indication System is adequately calibrated and can be used for indication of the measurement of control rod bank position.
A deviation of less than the allowable limit given in LCO 3.1.4 in position indication for a single control rod ensures high confidence that the position uncertainty of the corresponding control rod group is within the assumed values used in the analysis (that specified control rod group insertion limits).
These requirements provide adequate assurance that control rod position indication during power operation and PHYSICS TESTS is accurate, and that design assumptions are not challenged. OPERABILITY of the position indicator channels ensures that inoperable, misaligned, or mispositioned control rods can be detected. Therefore, power peaking, ejected rod worth, and SDM can be controlled within acceptable limits.
APPLICABILITY The requirements on the DRPI and step counters are only applicable in MODES 1 and 2 (consistent with LCOs 3.1.4, 3.1.5, and 3.1.6), because these are the only MODES in which power is generated, and the OPERABILITY and alignment of rods has the potential to affect the safety of the plant. In the shutdown MODES, the OPERABILITY of the shutdown and control banks has the potential to affect the required SDM, but this effect can be compensated for by an increase in the boron concentration of the Reactor Coolant System (RCS).
AP1000 STS B 3.1.7-3 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 18 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS The ACTIONS table is modified by a Note indicating that a separate Condition entry is allowed for each inoperable rod position indicator per group and each demand position indicator per bank. This is acceptable because the Required Actions for each Condition provide appropriate compensatory actions for each inoperable position indicator.
A.1
When one DRPI channel per group fails, the position of the rod can still be determined by use of the On-line Power Distribution Monitoring System (OPDMS). Based on experience, normal power operation does not require excessive movement of banks. If a bank has been significantly moved, the Actions of C.1 or C.2 below are required.
Therefore, verification of RCCA position within the Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate to allow continued full power operation, since the probability of simultaneously having a rod significantly out of position and an event sensitive to that rod position is small.
A.2
Reduction of THERMAL POW ER to 50% RTP puts the core into a condition where rod position is not significantly affecting core peaking factors (Ref. 2).
The allowed Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is reasonable, based on operating experience, for reducing power to 50% RTP from full power conditions without challenging plant systems and allowing for rod position determination by Required Action A.1 above.
B.1, B.2, B.3, and B.4
When more than one DRPI per group fail, additional actions are necessary to ensure that acceptable power distribution limits are maintained, minimum SDM is maintained, and the potential effects of rod misalignment on associated accident analyses are limited. Placing the Rod Control System in manual assures unplanned rod motion will not occur. Together with the indirect position determination available via incore detectors will minimize the potential for rod misalignment. The immediate Completion Time for placing the Rod Control System in manual reflects the urgency with which unplanned rod motion must be prevented while in this Condition.
AP1000 STS B 3.1.7-4 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 19 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS (continued)
Monitoring and recording reactor coolant Tavg help assure that significant changes in power distribution and SDM are avoided. The once per hour Completion Time is acceptable because only minor fluctuations in RCS temperature are expected at steady state plant operating conditions.
The position of the rods may be determined indirectly by use of the incore detectors. The Required Action may also be satisfied by N
E ensuring at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> that FQ satisfies LCO 3.2.1, FHA satisfies LCO 3.2.2, and SDM is within the limits provided in the COLR, provided the nonindicating rods have not been moved. Verification of control rod position once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate for allowing continued full power operation for a limited, 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period, since the probability of simultaneously having a rod significantly out of position and an event sensitive to that rod position is small. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time provides sufficient time to troubleshoot and restore the DRPI system to operation while avoiding the plant challenges associated with the shutdown without full rod position indication.
Based on operating experience, normal power operation does not require excessive rod movement. If one or more rods has been significantly moved, the Required Action of C.1 and C.2 below is required.
C.1 and C.2
These Required Actions clarify that when one or more rods with inoperable position indicators have been moved in excess of 24 steps in one direction since the position was last determined, the Required Actions of A.1 and A.2 or B.1 are still appropriate but must be initiated promptly under Required Action C.1 to begin verifying that these rods are still properly positioned relative to their group positions.
If, within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the rod positions have not been determined, THERMAL POW ER must be reduced to 50% RTP within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to avoid undesirable power distributions that could result from continued operation at > 50% RTP, if one or more rods are misaligned by more than 24 steps.
T alle d Cion Time of 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />sridesctablriod ofime tvifyod pitions.
AP1000 STS B 3.1.7-5 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 20 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS (continued)
D.1.1 and D.1.2
With one demand position indicator per bank inoperable, the rod positions can be determined by the DRPI System. Since normal power operation does not require excessive movement of rods, verification by administrative means that the rod position indicators are OPERABLE and the most withdrawn rod and the least withdrawn rod are 12 steps apart within the allowed Completion Time of once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate.
D.2
Reduction of THERMAL POW ER to 50% RTP puts the core into a condition where rod position is not significantly affecting core peaking factor limits (Ref. 2). The allowed Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> provides an acceptable period of time to verify the rod positions per Required Actions D.1.1 and D.1.2 or reduce power to 50% R T P.
E.1
If the Required Actions cannot be completed within the associated Completion Time, the plant must be brought to a MODE in which the requirement does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The allowed Completion Time is reasonable, based on operating experience, for reaching the required MODE from full power conditions in an orderly manner and without challenging plant systems.
SURVEILLANCE SR 3.1.7.1 REQUIREMENTS Verification that the DRPI agrees with the demand position within 12 steps provides assurance that the DRPI is operating correctly. Since the DRPI does not display the actual shutdown rod positions between 18 and 249 steps, only points within the indicated ranges are compared.
This surveillance is performed prior to reactor criticality after each removal of the reactor head, as there is the potential for unnecessary plant transients if the SR were performed with the reactor at power.
AP1000 STS B 3.1.7-6 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 21 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
REFERENCES 1. 10 CFR 50, Appendix A, GDC 13.
- 2. FS AR Chapter 15, Accident Analysis.
AP1000 STS B 3.1.7-7 Amendment 0Rev. 0 Revision 19 Date report generated:
Tuesday, June 02, 2015 Page 22 GTST AP1000- B17-3.1.7, Rev. 1
XII. Applicable STS Subsection After Incorporation of this GTSTs Modifications
The entire subsection of the Specifications and the Bases associated with this GTST, following incorporation of the modifications, is presented next.
Date report generated:
Tuesday, June 02, 2015 Page 23 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
3.1 REACTIVITY CONTROL SYSTEMS
3.1.7 Rod Position Indication
LCO 3.1.7 The Digital Rod Position Indication (DRPI) System and the Bank Demand Position Indication System shall be OPERABLE.
APPLICABILITY: MODES 1 and 2.
ACTIONS
NOTE -----------------------------------------------------------
Separate Condition entry is allowed for each inoperable rod position indicator and each demand position indicator.
CONDITION REQUIRED ACTION COMPLETION TIME
A. One DRPI per group A.1 Verify the position of the Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> inoperable for one or rods with inoperable more groups. position indicators by using the On-line Power Distribution Monitoring System (OPDMS).
A.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
B. More than one DRPI per B.1 Place the control rods Immediately group inoperable. under manual control.
AND
B.2 Monitor and record Reactor Once per 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Coolant System (RCS) Tavg.
AND
AP1000 STS 3.1.7-1 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 24 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME
B. (continued) B.3 Verify the position of the Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> rods with inoperable position indicators indirectly by using the incore detectors.
AND
B.4 Restore inoperable position 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> indicators to OPERABLE status such that a maximum of one DRPI per group is inoperable.
C. One or more rods with C.1 Verify the position of the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> inoperable position rods with inoperable indicators have been position indicators by using moved in excess of the OPDMS.
24 steps in one direction since the last OR determination of the rod s position. C.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
D. One demand position D.1.1 Verify by administrative Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> indicator per bank means all DRPIs for the inoperable for one or affected banks are more banks. OPERABLE.
AND
D.1.2 Verify the most withdrawn Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> rod and the least withdrawn rod of the affected banks are 12 steps apart.
AP1000 STS 3.1.7-2 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 25 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication 3.1.7
ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME
D. (continued) D.2 Reduce THERMAL 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> POW ER to 50% R T P.
E. Required Action and E.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met.
SURVEILLANCE REQUIREMENTS
SURVEILLANCE FREQUENCY
SR 3.1.7.1 Verify each DRPI agrees within 12 steps of the group Once prior to demand position for the full indicated range of rod criticality after travel. each removal of the reactor head
AP1000 STS 3.1.7-3 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 26 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
B 3.1 REACTIVITY CONTROL SYSTEMS
B 3.1.7 Rod Position Indication
BASES
BACKGROUND According to GDC 13 (Ref. 1), instrumentation to monitor variables and systems over their operating ranges during normal operation, anticipated operational occurrences (AOOs), and accident conditions must be OPERABLE. LCO 3.1.7 is required to ensure OPERABILITY of the control rod position indicators to determine control rod positions and thereby ensure compliance with the control rod alignment and insertion limits.
The OPERABILITY, including position indication, of the shutdown and control rods is an initial assumption in the safety analyses that assume rod insertion upon reactor trip. Maximum rod misalignment is an initial assumption in the rod cluster control assembly (RCCA) misalignment safety analysis that directly affects core power distributions and assumptions of available SDM. Rod position indication is required to assess OPERABILITY and misalignment.
Mechanical or electrical failures may cause a control rod to become inoperable or to become misaligned from its group. Control rod inoperability or misalignment may cause increased power peaking due to the asymmetric reactivity distribution and a reduction in the total available rod worth for reactor shutdown. Therefore, control rod alignment and OPERABILITY are related to core operation in design power peaking limits and the core design requirement of a minimum SDM.
Limits on control rod alignment and OPERABILITY have been established, and rod positions are monitored and controlled during power operation to ensure that the power distribution and reactivity limits defined by the design power peaking and SDM limits are preserved.
RCCAs, or rods, are moved out of the core (up or withdrawn) or into the core (down or inserted) by their control rod drive mechanisms. The RCCAs are divided among control banks and shutdown banks. Each bank may be further subdivided into two groups to provide for precise reactivity control.
The axial position of shutdown rods and control rods are determined by two separate and independent systems: the Bank Demand Position Indication System (commonly called group step counters) and the Digital Rod Position Indication (DRPI) System.
AP1000 STS B 3.1.7-1 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 27 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
BACKGROUND (continued)
The Bank Demand Position Indication System counts the pulses from the Rod Control System that move the rods. There is one step counter for each group of rods. Individual rods in a group receive the same signal to move and should, therefore, be at the same position indicated by the group step counter for that group. The Bank Demand Position Indication System is considered highly precise (+/- 1 step or +/- 5/8 inch). If a rod does not move one step for each demand pulse, the step counter will still count the pulse and incorrectly reflect the position of the rod.
The DRPI System provides a highly accurate indication of actual control rod position, at a lower precision than the step counters. This system is based on inductive analog signals from a series of coils spaced along a hollow tube with a center to center distance of 3.75 inches, which is 6 steps. To increase the reliability of the system, the inductive coils are connected alternately to data system A or B. Thus, if one system fails, the DRPI will function at half accuracy with an effective coil spacing of 7.5 inches, which is 12 steps. Therefore, the normal indication accuracy of the DRPI System is +/- 6 steps (+/- 3.75 inches), and the maximum uncertainty is +/- 12 steps (+/- 7.5 inches). W ith an indicated deviation of 12 steps between the group step counter and DRPI, the maximum deviation between actual rod position and the demand position could be 24 steps, or 15 inches.
APPLICABLE Control and shutdown rod position accuracy is essential during power SAFETY operation. Power peaking, ejected rod worth, or SDM limits may be ANALYSES violated in the event of a Design Basis Accident (Ref. 2), with control or shutdown rods operating outside their limits undetected. Therefore, the acceptance criteria for rod position indication is that rod positions must be known with sufficient accuracy in order to verify the core is operating within the group sequence, overlap, design peaking limits, ejected rod worth, and with minimum SDM (LCO 3.1.5, Shutdown Bank Insertion Limits, LCO 3.1.6, Control Bank Insertion Limits ). The rod positions must also be known in order to verify the alignment limits are preserved (LCO 3.1.4, Rod Group Alignment Limits ). Control rod positions are continuously monitored to provide operators with information that assures the plant is operating within the bounds of the accident analysis assumptions.
The control rod position indicator channels satisfy Criterion 2 of 10 CFR 50.36(c)(2)(ii). The control rod position indicators monitor control rod position, which is an initial condition of the accident.
AP1000 STS B 3.1.7-2 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 28 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
LCO LCO 3.1.7 specifies that one DRPI System and one Bank Demand Position Indication System be OPERABLE for each control rod. For the control rod position indicators to be OPERABLE requires meeting the SR of the LCO and the following:
- a. The DRPI System indicates within 12 steps of the group step counter demand position as required by LCO 3.1.4, Rod Group Alignment Limits ;
- b. For the DRPI System there are no failed coils; and
- c. The Bank Demand Indication System has been calibrated either in the fully inserted position or to the DRPI System.
The 12 step agreement limit between the Bank Demand Position Indication System and the DRPI System indicates that the Bank Demand Position Indication System is adequately calibrated and can be used for indication of the measurement of control rod bank position.
A deviation of less than the allowable limit given in LCO 3.1.4 in position indication for a single control rod ensures high confidence that the position uncertainty of the corresponding control rod group is within the assumed values used in the analysis (that specified control rod group insertion limits).
These requirements provide adequate assurance that control rod position indication during power operation and PHYSICS TESTS is accurate, and that design assumptions are not challenged. OPERABILITY of the position indicator channels ensures that inoperable, misaligned, or mispositioned control rods can be detected. Therefore, power peaking, ejected rod worth, and SDM can be controlled within acceptable limits.
APPLICABILITY The requirements on the DRPI and step counters are only applicable in MODES 1 and 2 (consistent with LCOs 3.1.4, 3.1.5, and 3.1.6), because these are the only MODES in which power is generated, and the OPERABILITY and alignment of rods has the potential to affect the safety of the plant. In the shutdown MODES, the OPERABILITY of the shutdown and control banks has the potential to affect the required SDM, but this effect can be compensated for by an increase in the boron concentration of the Reactor Coolant System (RCS).
AP1000 STS B 3.1.7-3 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 29 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS The ACTIONS table is modified by a Note indicating that a separate Condition entry is allowed for each inoperable rod position indicator per group and each demand position indicator per bank. This is acceptable because the Required Actions for each Condition provide appropriate compensatory actions for each inoperable position indicator.
A.1
When one DRPI channel per group fails, the position of the rod can still be determined by use of the On-line Power Distribution Monitoring System (OPDMS). Based on experience, normal power operation does not require excessive movement of banks. If a bank has been significantly moved, the Actions of C.1 or C.2 below are required.
Therefore, verification of RCCA position within the Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate to allow continued full power operation, since the probability of simultaneously having a rod significantly out of position and an event sensitive to that rod position is small.
A.2
Reduction of THERMAL POW ER to 50% RTP puts the core into a condition where rod position is not significantly affecting core peaking factors (Ref. 2).
The allowed Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is reasonable, based on operating experience, for reducing power to 50% RTP from full power conditions without challenging plant systems and allowing for rod position determination by Required Action A.1 above.
B.1, B.2, B.3, and B.4
When more than one DRPI per group fail, additional actions are necessary to ensure that acceptable power distribution limits are maintained, minimum SDM is maintained, and the potential effects of rod misalignment on associated accident analyses are limited. Placing the Rod Control System in manual assures unplanned rod motion will not occur. Together with the indirect position determination available via incore detectors will minimize the potential for rod misalignment. The immediate Completion Time for placing the Rod Control System in manual reflects the urgency with which unplanned rod motion must be prevented while in this Condition.
AP1000 STS B 3.1.7-4 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 30 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS (continued)
Monitoring and recording reactor coolant Tavg help assure that significant changes in power distribution and SDM are avoided. The once per hour Completion Time is acceptable because only minor fluctuations in RCS temperature are expected at steady state plant operating conditions.
The position of the rods may be determined indirectly by use of the incore detectors. The Required Action may also be satisfied by N
E ensuring at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> that FQ satisfies LCO 3.2.1, FA A H
satisfies LCO 3.2.2, and SDM is within the limits provided in the COLR, provided the nonindicating rods have not been moved. Verification of control rod position once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate for allowing continued full power operation for a limited, 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period, since the probability of simultaneously having a rod significantly out of position and an event sensitive to that rod position is small. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time provides sufficient time to troubleshoot and restore the DRPI system to operation while avoiding the plant challenges associated with the shutdown without full rod position indication.
Based on operating experience, normal power operation does not require excessive rod movement. If one or more rods has been significantly moved, the Required Action of C.1 and C.2 below is required.
C.1 and C.2
These Required Actions clarify that when one or more rods with inoperable position indicators have been moved in excess of 24 steps in one direction since the position was last determined, the Required Actions of A.1 and A.2 or B.1 are still appropriate but must be initiated promptly under Required Action C.1 to begin verifying that these rods are still properly positioned relative to their group positions.
If, within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the rod positions have not been determined, THERMAL POW ER must be reduced to 50% RTP within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to avoid undesirable power distributions that could result from continued operation at > 50% RTP, if one or more rods are misaligned by more than 24 steps.
T alle d Cion Time of 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />sridesctablriod ofime tvifyod pitions.
AP1000 STS B 3.1.7-5 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 31 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
ACTIONS (continued)
D.1.1 and D.1.2
With one demand position indicator per bank inoperable, the rod positions can be determined by the DRPI System. Since normal power operation does not require excessive movement of rods, verification by administrative means that the rod position indicators are OPERABLE and the most withdrawn rod and the least withdrawn rod are 12 steps apart within the allowed Completion Time of once every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is adequate.
D.2
Reduction of THERMAL POW ER to 50% RTP puts the core into a condition where rod position is not significantly affecting core peaking factor limits (Ref. 2). The allowed Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> provides an acceptable period of time to verify the rod positions per Required Actions D.1.1 and D.1.2 or reduce power to 50% R T P.
E.1
If the Required Actions cannot be completed within the associated Completion Time, the plant must be brought to a MODE in which the requirement does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The allowed Completion Time is reasonable, based on operating experience, for reaching the required MODE from full power conditions in an orderly manner and without challenging plant systems.
SURVEILLANCE SR 3.1.7.1 REQUIREMENTS Verification that the DRPI agrees with the demand position within 12 steps provides assurance that the DRPI is operating correctly. Since the DRPI does not display the actual shutdown rod positions between 18 and 249 steps, only points within the indicated ranges are compared.
This surveillance is performed prior to reactor criticality after each removal of the reactor head, as there is the potential for unnecessary plant transients if the SR were performed with the reactor at power.
AP1000 STS B 3.1.7-6 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 32 GTST AP1000- B17-3.1.7, Rev. 1
Rod Position Indication B 3.1.7
BASES
REFERENCES 1. 10 CFR 50, Appendix A, GDC 13.
- 2. FSAR Chapter 15, Accident Analysis.
AP1000 STS B 3.1.7-7 Rev. 0
Date report generated:
Tuesday, June 02, 2015 Page 33