ML19332F095
| ML19332F095 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/04/1989 |
| From: | Butler W Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19332F096 | List: |
| References | |
| NUDOCS 8912130397 | |
| Download: ML19332F095 (24) | |
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o UNITED STATES
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i NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 I
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PHILADELPHIA ELECTRIC COMPANY PUBLIC SERVICE _-ELECTRIC AND GAS COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY DOCKET NO. 50-277 PEACH BOTTOM ATOMIC POWER STATION, UNIT 140. 2 AMENDMENT TO FACILITY OPERATING LICENSE Amendment -tio.151 License No. DPR-44 1.
The Nuclear Regulatory Commission-(the Commission) has found that:
A.
The application for amendment by Philadelphia Electric Company,.
(thelicensee)datedJuly 19, 1989, as supplemented by a November 14, 1989 letter, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Comission's rules and regulations set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the
' Comission; C.
There.is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and
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safety of the public, and (ii) that such activities will be conducted in compliance with the Comission's regulations; D.
The issuance of this amendment will not be inimical to the common defense and. security, or to-the health and safety.of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Comission's regulations and all applicable requirements have been satisfied.
2.
Accordingly the license is amended by changes to the Technical Specifications, as indicated in the attachment to this license amendment, and paragraph 2.C(2) of Facility Operating License No. DPR-44 is hereby amended to read
.as follows:
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8912130397 891204 PDR ADOCK 05000277 P
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- .. (2)
Technical Specifications The Technical Speci#ications contained in Appendices A and B, as revited through Amendment No.151, are hereby incorporated in the license.
PECO shall operate the facility in accordance with the Technical Specifications.
3.
This license amendment is effective as of its date of issuance.
FOR THE NUCLEAR DEGULATORY COMMISSION e
4 I
Walter P. Butler Director Project Directorate i-2 Division of Reactor Projects I/II
Attachment:
Chances to the Technical Specifications Date of Issuance:
December 4, 1989 I
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L ATTACHMENT TO LICENSE AMENDVENT NO. 151 FACILITY OPERATING LICENSE NO. OpR-44
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D_0CKET NO. 50-277 Peplace the following papet of the Appendix A Technical Specifications with the enciesed pages.
The revir.ed areas are indicated by marginal lires, Remove Insert 19 19 99 99 100 100 101 101 1
102 102 10Ea 102a 107 107 108 108 109 109 i
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a.
PBAPS UNIT 2 2.1. A BASES (Cont'd.)
An increase in the APRM scram trip setting would decrease the margin present before the fuel cladding integrity Safety Limit is reached.
The APRM scram trip setting was determined by an analysis of margins required to provide a reasonable range for maneuvering during operation.
Reducing this operating margin would increase the frequency of spurious scrams which have an adverse effect on reactor safety because of the resulting thermal stresses.
Thus, the APRM scram trip setting was selected because it provides adequate margin for the fuel cladding integrity Safety Limit yet allows operating margin that reduces th' possibility of unnecessary scrams.
The scram trip setting must be adjusted to assure that the LHGR transient peak is not increased for any combination of maximum fraction of limiting power den-sity (MFLPD) and reactor core thermal power.
The scram setting is adjusted in accordance with the formula in Specification 2.1.A.1, when the MFLPD is greater than the fraction of rated power (FRP).
Analyses of the limiting transients show that no scram aajustment is required to assure MCPR greater than the fuel cladding integrity safety limit when the transient is initiated from MCPR greater than the operating limit given in Specification 3.5.K.
For operation in the startup mode while the reactor is at low pressure, the APRM scram setting of 15 percent of rated power provides adequate thermal mar-gin between the setpoint and the Safety Limit, 25 percent of rated.
The margin is adequate to accommodate anticipated maneuvers associated with power plant startup.
Effects of increasing pressure at zero or low void content are Ininor, cold water from sources available during startup is not much colder than that already in the system, temperature coefficients are small, and control rod pat-terns are constrained to be uniform by operating procedures backed up by the Rod Worth Minimizer.
Worth of individuai rods is very low in a uniform rod pattern.
Thus, of all possible sources of reactivity input, uniform control rod with-drawai is the most probable cause of significant power rise.
Because the flux distribution associated with uniform rod withdrawals does not involve high local peaks, and because several rods must be moved to change power by a significant percentage of rated power, the rate of change of power is very slow.
Generally, the heat flux is in near equilibrium with the fission rate.
In an assumed uni-form rod withdrawal approach to the scram level, the rate of power rise is no more than 5 percent of rated power per minute, and the APRM system would be more than adequate to assure a scram before the power could exceed the Safety Limit.
The 15 percent APRM scram remains active until the mode switch is placed in the RUN position.
This switch occurs when the reactor pressure is greater than 850 psig.
Amendment No M, FS, 70,151 19
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PBAPS UNIT 2 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3 REACTIVITY CONTROL 4.3 REACTIVITY CONTROL Applicability:
Applicability:
Applies to the operational Applies to the surveillance status of the control rod requirements of the control system.
rod system.
Objective:
Objective:
To assure the ability of the To verify the ability of the control rod system to control rod system to control reactivity, control reactivity.
Specification:
Specification:
A. Reactivity Limitations A.
Reactivity Limitations
- 1. Reactivity margin -
1.
Reactivity margin -
core loading core loading A sufftcient number of control Suf ficient control rods shall t
rods shall be operable 50 be withdrawn following a that the core could be made refueling outage when core suberitical in the most alterations were performed to reactive condition during the demonstrate with a margin of operating cycle with the 0.38%ik/k that the core can strongest control rod fully be made suberitical at any withdrawn and all other time in the subsequent fuel operable control rods fully cycle with the analytically
- inserted, determined strongest operable control rod fully withdrawn and all other operable-rods fully inserted.
- 2. Reactivity margin -
2.
Reactivity margin -
inoperable control rods inoperable control rods
- a. Control rods which cannot
- a. Each partially or fully be moved with control rod withdrawn operable control drive pressure shall be r'd shall be exercised one considered inoperable.
notch at least once each week when operating above If a partially or fully the RWM low power setpoint.
withdrawn control rod drive Each partially or fully cannot be moved with drive withdrawn operable control or scram pressure the rod shall be exercised at reactor shall be brought least one notch at laast to a shutdown condition every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when operating within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> unless above the RWM low power setpoint if there are three Amendment No. U. H.151 99 l
PBAPS UNIT 2 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.A Reactivity Limitations 4.3.A Reactivity Limitations (Cont'd)
(Cont'd) investigation demonstrates or more inoperable control rods that the cause of the or when operating above the RWM failure is not due to a low power setpoint if there is failed control rod drive one fully or partially withdrawn mechanism collet housing.
rod which cannot be moved and for which control rod drive mechanism damage has not been ruled out.
The surveillance need not be completed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if the number of inoper-able rods has been reduced to less than 3 and if it has been demonstrated that control rod drive mechanism collet housing failure is not the cause of an immovable control rod.
- b. The control rod directional
- b. The scram discharge volume control valves for inoperable drain and vent valves shall control rods shall be disarmed be verified open at least electrically and the control once per month.
These valves rods shall be in such positions may be closed intermittently that Specification 3.3.A.1 for testing, is met,
- c. Control rods with scram times
- c. At least once every 3 months greater than those permitted verify that the scram discharge by Specification 3.3.C.3 are volume drain and vent valves inoperable, but if they can closed within 15 seconds after be inserted with control rod receipt of a closure signal, drive pressure they need not and reopen upon reset of the be disarmed electrically.
closure signal.
- d. Deleted.
- d. Deleted.
- e. Control rods with inoperable accumulators or those whose position cannot be positively I
determined shall be considered inoperable.
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Amendment No. 17, #3, 88, 151
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PBAPS UNIT 2 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3,A Reactivity Limitations 4.3.A Reactivity Limitations (Cont'd)
(Cont'd)
- f. Inoperable controls rods shall be positioned such that Specification 3.3.A.1 is met.
In addition, during reactor power operation, no more than one control rod in any 5 x 5 array may be inoperable (at least 4 operable control rods must separate any 2 inopere.ble ones),
If this Specification cannot be met the reactor shall not be started, or if at power, the reactor shall be brought to a cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
B. Control Rods B.
Control Rods 1, Each control rod shall be 1.
The coupling integrity shall counled to its drive or be verified for each withdrawn completely inserted and control rod as follows:
the control rod directional control valves disartned a When a rod is withdrawn electrically.
This require-the first time after each ment does not apply in the refueling outage or after refuel condition when the maintenance, observe dis-reactor is vented.
Two cernible response of the control rod drives may be nuclear instrumentation and removed as long as rod position indication for Specification 3.3,A.1 is met, the " full-in" and " full-out" position.
However, for initial rods when response is not discernible, subsequent exercising of these rods 6fter the reactor is above the Rod Worth Minimizer low power setpoint shall be performed to verify instrumentation response, b, When the rod is fully withdrawn the first time after each refueling outage or after maintenance observe that the drive does not go to the overtravel position.
Amendment No. #3, 151 191
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PBAPS UNIT 2 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS l
'i 3.3.B Control Cods (Cont'd) 4.3.B Control Rods (Cont'd)
- c. During each refueling outage and af ter control rod maintenance, observe that the drive does not go to the overtravel position.
- 2. The control rod drive housing 2.
The control rod drive housing support system shall be in support system shall be in-place during reactor power spected after reassembly and operation or when the reactor the results of the Inspection coolant system is pressurized
- recorded, above atmospheric pressure with fuel in the reactor vessel, unless all control rods are fully inserted and Specification 3.3.A.1 is met.
- 3. a. Deleted.
3.
- a. Deleted.
- b. The Rod Worth Minimizer
- b. 1. Prior to the start of control (RWM) low power setpoint rod withdrawal towards criti-is greater than or equal to cality and prior to attaining 10% of rated power.
Whenever the Rod Worth Minimizer low the reactor is in the startup power setpoint during rod or run modes with thermal-insertion at shutdown, the Rod power less than or equal to Worth Minimizer (RWM) shall be the Rod Worth Minimizer demonstrated to be operable by (RWM) low power setpoint the the following checks:
Rod Worth Minimizer shall be operable except as follows:
- a. The RWM computer on line diagnostic test shall be
- 1. With the RWM inoperable after the successfully performed, first 12 control rods are fully withdrawn, operation may continue
- b. Prior to the start of
.provided that control rod movement control rod withdrawal only, and compliance with the prescribed proper annunciation of the control rod pattern are verified selection error of at least by a second licensed operator or one out-of-sequence control technically qualified member of the rod in a fully inserted station technical staff.
group shall be verified.
Amendment No. 23, #3,151
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r-w PBAPS UNIT 2 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.B Control Rods (Cont'd) 4.3.B Control Rods (Cont'd)
- c. The rod block function of the RWM shall be verified by withdrawing the first rod during start-up only as an out-of-sequence control rod no more than to the block point.
- 2. With the RWM inoperable before the
- 2. Following any loading of the first 12 control rods are fully rod worth minimizer sequence withdrawn, one startup per calendar program into the computer, year may be performed provided that the correctness of the con-control rod movement and compliance trol rod withdrawal sequence with the prescribed control rod input to the RWM computer pattern are verified by a second shall be verified.
licensed operator or technically qualified member of the station technical staff.
- 3. Otherwise, with the RWM inoperable, control rod withdrawal movement shall not be permitted except by full scram.
Control rods may be moved, under administrative control to permit testing associated with demonstrating operability of the RWM.
- c. Deleted.
- c. When required, the presence of the second licensed operator or technically qualified member of the station technical staff to verify the following of the correct rod program shall be verified and recorded.
Amendment No. 23, 43, f 7,151
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PBAPS UNIT 2 l
3.3.A and 4.3.A BASES (Cont'd)
Studies have been made which compare experimental criticals with calculated criticals.
These studies have shown that actual criticals can be predicted within a given tolerance band.
For gadolinia cores the additional margin required due to control cell material manufacturing tolerances and calculational uncertainties has experimentally been determined to be 0.38% Ak/k.
When this l
additional margin is demonstrated, it assures that the reactivity control requirement is met.
2.
Reactivity Marcin - Inoperable Control Rods Specification 3.3.A.2 requires that a rod be taken out of service if it cannot be moved with drive pressure. -If the rod is fully inserted and then disarmed electrically *, it is in a safe position of maximum contribution to shut down reactivity.
If it is disarmed electrically in a non-fully inserted position, that position shall be consistent with the shutdown reactivity limitation stated in Specification 3.3.A.1.
This assures that the core can be shutdown at all times with the remaining control rods assuming the strongest operable control rod does not insert.
Inoperable bypassed rods will be limited within any group to not more than one control rod of a (5x5) twenty-five control rod array.
Also if damage within the control rod drive mechanism and in particular, cracks in drive internal housings, cannot be ruled out, then 4 generic problem affec-ting a number of drives cannot be ruled out.
Circumferential cracks resulting from stress assisted intergranular corrosion have occurred in the collet hous-ing of drives at several BWRs.
This type of cracking could occur in a number of drives and if the cracks propagated until severance of the collet housing-occurred, scram could be prevented in the affected rods.
Limiting the period of operation with a potentially severed rod and requiring increased surveil-lance after detecting one' stuck rod will assure that the reactor will not be operated with a large number of rods with failed collet housings.
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- To disarm the drive electrically, four Amphenol type plug connectors are removed from the drive insert and withdrawal solenoids rendering the rod incapable of withdrawal.
This procedure is equivalent to valving out the drive and is preferred because, in this condition, drive water cools and minimizes crud accumulation in the drive.
Electrical disarming does not l
eliminate position indication.
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Amendment No. H.151 107-
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PBAPS UNIT 2 3.3 and 4.3 BASES (Cont'd)
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B.
Control Rods 1.
Control rod dropout accidents as discussed in the FSAR can lead to significant core damage.
If coupling integrity is maintained, the possibility of a rod drop-I out accident is eliminated.
The overtravel position feature provides a positive check as only uncoupled drives may reach this position.
Neutron instrumentation response to rod movement provides a verification that the rod is following its drive.
Absence of such response to drive movement could indicate an uncoupled condition.
Rod position indication is required for proper function of the rod worth minimizer (RWM).
2.
The control rod housing support restricts the outward movement of a control rod to less than 3 inches in the extremely remote event of a housing failure.
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The amount of reactivity which could be added by this small amount of rod with-drawal, which is less than a normal single withdrawal increment, will not con-tribute to any damage to the primary coolant system.
The design basis is given in subsection 3.5.2 of the FSAR and the safety evaluation is given in subsection 3.5.4.
This support is not required if the reactor coolant system is at atmos-pheric pressure since there would then be no driving force to rapidly eject a drive housing.
Additionally, the support is not required if all control rods are fully inserted and if an adequate shutdown margin with one control rod with-drawn has been demonstrated, since the reactor would remain subcritical even in the event of complete ejection of the strongest control rod.
3.
The Rod Worth Minimizer (RWM) restricts withdrawals and insertions of control-rods to prespecified sequences.
All patterns associated with these restrictions have the characteristic that, assuming the worst single deviation from the restrictions, the drop of any control rod from the fully inserted position to the position of the control rod drive would not cause the reactor to sustain a power excursion resulting in the peak enthalpy of any pellet exceeding 280 calories per gram.
An enthalpy of 280 calories per gram is well below the level at which rapid fuel dispersal could occur (i.e., 425 calories per gram).
Primary system damage in this accident is not possible unless a significant amount of fuel is rapidly dispersed.
Ref. Sections 3.6.6, 14.6.2 and 7.16.3.3 of the FSAR, NED0-10527 and supplements thereto, and NEDE-24011-P-A.
1 Amendment No.17 M, #8, 70,151
-108-l n
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PBAPS UNIT 2 3.3.B and 4.3.B BASES (Cont'd)
In performing the function described above, the RWM is not needed to impose any restrictions at core power levels in excess of 10 percent of rated power.
Mate-rial in the cited references shows that it is impossible to reach 280 calories per gram in the event of a control rod drop occurring at a power level greater than 10 percent, regardless of the rod pattern.
This is true for all normal and l
abnormal patterns, including those which maximize individual control rod worth, i
The Rod Worth Minimizer provides automatic supervision to assure that out-of-sequence control rods will not be withdrawn or inserted; i.e., the RWM system limits operator deviations from planned control rod movement.
The RWM is an important system for minimizing the consequences of an RDA below 10% power.
The RWM is therefore required to be operable for all but one startup per year before the first twelve control rods are fully withdrawn.
One startup per year before the first twelve control rods are fully withdrawn will be permitted with the RWM inoperable provided control rod movement and compliance with the pre-scribed control rod pattern are verified by a second licensed operator or tech-nically qualified member of the station technical staff.
The function of the i
RWM makes it unnecessary to specify a license limit on rod worth to preclude unacceptable consequences in the event of a control rod drop.
At power levels below 10 percent of rated, the RWM forces adherence to acceptable rod patterns.
Above 10 percent of rated power, no constraint on rod pattern is required to assure that rod drop accident consequences are acceptable.
Control rod pattern constraints above 10 percent of rated power are imposed by power distribution l
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requirements as defined in Section 3.5/4.5 of the Technical Specifications.
4.
The Source Range Monitor (SRM) system performs no automatic safety system function; i.e., it has no scram function.
It does provide the operator with a visual indication of neutron level.
The consequences of reactivity accidents are functions of the initial neutron flux.
Amendment No. 23, 36, #3, 151
-109-
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UNITED STATES NUCLE AR REGULATORY COMMISSION
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PHILADELPHIA ELECTRIC COMPANY PUBLIC SERVICE ELECTRIC AND GA5 COMPANY DELMARVA POWER AND LIGHT CCMPANY ATLANTIC CITY ELECTRIC CUPPANY l
DOCKET NO. 50-278 t
PEACH BOTTOM ATOMIC POWER STATION. UNIT NO. 3 t
i AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 153 License No. DPR-56 1.
The Nuclear Regulatory Commission (the Comission) has found that:
A.
The application for amendment by Philadelphia Electric Company, et al. (the licensee) dated July 19, 1989, as supplemented by a November 14, 1989 letter, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Comission's rules and reguistions set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commissien; C.
Thereisreasonableassurance(i)thattheactivitiesauthorizedby
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this-arendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; L
D.
The issuance of this amendment will ret be inimical to the comon L
defense and security, or to the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.
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2.
Accordingly the license is amended by changes to the Technical Specifications, as indicated in the attachment to this license amendment, and paragraph 2.C(2) of Facility Operating License No. DPR-ES is hereby amended to read as follows:
2 (2)
Technical Specifications The Technical Specifications contained in Appendice: A and B, as revised through Amendment No.153, are bereby incorporated in the 11censo.
pECO shall operate the facility in accordance with the Technical Specifications.
3.
This license amendment is effective as of its date of issuance.
FOR THE NUCLEAR REGl'LATORY COMMISSION Walter R. Butler. Director Project Directorate I-2 Division of Reactor Projects I/I!
Attachment:
Changes to the Technical Specifications Date of issuance: December 4, 1989 i
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ATTACHMENT TO LICENSE AMENDMENT NO.153 FACILITY OPERATING LICENSE NO. DPR-56 DOCKET NO. 50-278 Replace the followin the enclosed peges. g pages of the Appendix A Technical Specifications with The revised areas are indicated by marginal lines.
Remove insert l
19 19 t
99 99 100 100 101 101 102 102 102a 102a t
107 107 108 108 109 109 I
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I PBAPS UNIT 3 2.1.A BASES (Cont'd.)
An increase in the APRM scram trip setting would decrease the margin present before the fuel cladding integrity Safety Limit is reached.
The APRM scram trip setting was determined by an analysis of margins required to provide a reasonable range for maneuvering during operation.
Reducing this operating margin would increase the frequency of spurious scrams which have an adverse effect on reactor safety because of the resulting thermal stresses.
Thus, the APRM scram trip setting was selected because it provides adequate margin for the fuel cladding integrity Safety Limit yet allows operating margin that reduces the possibility of unnecessary scrams.
The scram trip setting must be adjusted to assure that the LHGR transient peak is not increased for any combination of maximum fraction of limiting power den-sity (MFLPD) and reactor core thermal power.
The scram setting is adjusted in accordance with the formula in Specification 2.1.A.1, when the MFLPD is greater than the fraction of rated power (FRP).
Analyses of the limiting transients show that no scram adjustment is required to assure MCPR greater than the fuel cladding integrity safety limit when the transient is initiated from MCPR greater than the operating limit given in Specification 3.5.K.
For operation in the startup mode while the reactor is at low pressure, the APRM scram setting of 15 percent of rated power provides adequate thermal mar-gin between the setpoint and the Safety Limit, 25 percent of rated.
The margin is adequate to accommodate anticipated maneuvers associated with power plant-startup.
Effects of increasing pressure at zero or low void content are minor, cold water from sources available during startup is not much colder than that already in the system, temperature coefficients are small, and control rod pat-terns are constrained to be uniform by operating procedures backed up by the Rod Worth Minimizer. Worth of individual rods is very low in a uniform rod pattern.
'Thus, of all possible sources of reactivity input, uniform control rod with-drawal is the most probable cause of significant power rise.
Because the flux distribution associated with uniform rod withdrawals does not involve high local peaks, and because several rods must be moved to change power by a significant percentage of rated power, the rate of change of power is very slow. Generally, the heat flux is in near equilibrium with the fission rate.
In an assumed uni-form rod withdrawal approach to the scram level, the rate of power rise is no more than 5 percent of rated power per minute, and the APRM system would be more than adequate to assure a scram before the power could exceed the Safety Limit.
The 15 percent APRM scram remains active until the mode switch is placed in the RUN position.
This switch occurs when the reactor pressure is greater than 850 psig.
Amendment No. 14, 41, 62, 79, 153.
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PBAPS UNIT 3
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LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3,3 REACTIVITY CONTROL 4.3 REACTIVITY CONTROL Applicability:
Applicability:
Applies to the operational Applies to the surveillance status of the coritrol rod requirements of the control
- system, rod system.
Objective:
Objective:
To assure the ability of the To verify the ability of the control rod system to control rod system to control reactivity.
control reactivity.
Specification:
Specification:
A, Reacti_vity Limitations A.
Reactivity Limitations 1, Reactivity margin -
1.
Reactivity margin -
core loading core loading A sufficient number of control Sufficient control rods shall rods shall be operable so be withdrawn following a that the core could be made refueling outage when core subcritical in the most alterations were performed to reactive. condition during the demonstrate with a margin of operating cycle with the 0.38%ak/k that the core can strongest control rod fully be made subcritical at any withdrawn and all other time in the subsequent fuel operable control rods fully cycle with the analytically
- inserted, determined strongest operable control rod fully withdrawn and all other operable rods fully inserted, 2, Reactivity margin -
2.
Reactivity margin -
inoperable control rods inoperable control rods
- a. Control rods which cannot
- a. Each partially or fully be moved with control rod withdrawn operable control 1
drive pressure shall be rod shall be exercised one considered inoperable.
notch at least once each week when operating above If a partially or fully the RWM low power setpoint, withdrawn control rod drive Each partially or fully cannot be moved with drive withdrawn operable control or scram pressure the rod shall be exercised at reactor shall be brought least one notch at least every to a shutdown condition 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when operating above j
within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> unless the RWM low power setpoint if i
there are three or more I
Amendment No. 16, 43. 153 99
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I PBAPS UNIT 3 s
LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.A Reactivity Limitations 4.3.A Reactivity Limitations (Cont'd)
(Cont'd) investigation demonstrates inoperable control rods or that the cause of the or when operating above the failure is not due to a RWM low power setpoint if there failed control rod drive is one fully or partially with-mechanism collet housing.
drawn rod which cannot be moved and for which control rod drive mechanism damage has not been ruled out.
The surveillance need not be completed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if the number of inoperable rods has been reduced to less than 3 and if it has been demonstrated that control rod drive mecha-nism collet housing failure is not the cause of an immovable control rod,
- b. The control rod directional
- b. The scram discharge volume control valves for inoperable drain and vent valves shall control rods shall be disarmed be verified open at least electrically and the control once per month.
These valves rods shall be in such positions may be closed intermittently that Specification 3.3.A.1 for testing.
is met.
- c. Control rods with scrism times
- c. At least once every 3 months greater than those permitted verify that the scram discharge by Specification 3.3.C.3 are volume drain and vent valves inoperable, but if they can closed within 15 seconds after be inserted with control rod receipt of a closure signal, drive pressure they need not and reopen upon reset of the be disarmed electrically, closure signal.
- d. Deleted,
- d. Deleted.
- e. Control rods with inoperable accumulators or those whose position cannot be positively determined shall be considered inoperable.
Amendment No. SS,153
-100-
b PBAPS UNIT 3
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LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.A Reactivity Limitations 4.3.A Reactivity Limitations (Cont'd)
(Cont'o)
- f. Inoperable controls rods shall i
be positiened such that i
Specification 3.3.A.1 is met.
In addition, during reactor power operation, no more than l
one control rod in any 5 x 5 array may be inoperable (at least 4 operable control rods must separate any 2 inoperable ones).
If this Specification cannot be met the reactor shall i
not be started, or if at power, the reactor shall be brought to a cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
B. Control Rods B.
- 1. Each control rod shall be 1.
The coupling integrity shall coupled to its drive or be verified for each withdrawn completely inserted and control rod as follows:
the control rod directional centrol valves disarmed
- a. When a rod is withdrawn electrically.
This require-the first time after each ment does not apply in the refueling outage or after refuel condition when the maintenance, observe dis-reactor is vented.
Two cernible response of the control rod drives may be nuclear instrumentation and removed as long as rod position indication for Specification 3.3.A.1 is met, the " full-in" and " full-out" position.
However, for initial rods when response is not discernible, subsequent exercising of these rods after the reactor is above the Rod Worth Minimizer low power setpoint shall be performed to verify instenmentation response.
- b. When the rod is fully withdrawn the first time after each refueling outage or after maintenance observe that the drive does not go to the overtravel position.
Amendment No. 16, 43, 153
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PBAPS UNIT 3 LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.B Control Rods (Cont'd) 4.3.B Control Rods (Cont'd)
- c. During each refueling outage and after control rod maintenance, observe that the Crive does not go to the overtravel position.
- 2. The control rod drive housing 2.
The control rod drive housing support system shall be in support system shall be in-place during reactor power spected after reassembly and operation or when the reactor the results of the Inspection coolant system is pressurized recorded.
above atmospheric pressure with fuel in the reactor vessel, unless all control rods are fully inserted and Specification 3.3.A.1 is met.
- 3. a. Deleted.
3.
- a. Deleted,
- b. The Rod Worth Minimizer
- b. 1. Prior to the start of control (RWM) low power setpoint rod withdrawal towards criti-is greater than or equal to cality and prior to attaining 10% of rated power.
Whenever the Rod Worth Minimizer low the reactor is in the startup power setpoint during rod or run modes with. thermal insertion at shutdown, the Rod power less than or e, qual to Worth Minimizer (RWM) shall be the Rod Worth Minimizer demonstrated to be operable by (RWM) low power setpoint the the following checks:
Rod Worth Minimizer shall be operable except as follows:
- a. The RWM computer on line
' diagnostic test shall be
- 1. With the RWM inoperable after the successfully performed, first 12 control rods are fully withdrawn, operation may continue
- b. Prior to the start of provided that control rod movement control rod withdrawal only, I
and compliance with the prescribed proper annunciation of the l
control rod pattern are verified selection error of at least by a second licensed operator or one out-of-sequence control technically qualified member of the rod in a fully inserted station technical staff, group shall be verified.
Amendment No. 33, 43. 153
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PBAPS UNIT 3
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LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.3.B Control Rods (Cont'd) 4.3.8 Control Rods (Cont'd)
- c. The rod block function of the RWM shall be verified by withdrawing the first rod during start-up only as an out-of-sequence control rod no more than to the block point.
- 2. With the RWM inoperable before the
- 2. Following any loading of the first 12 control rods are fully rod worth minimizer sequence withdrawn, one startup per calendar program into the computer, year may be performed provided that the correctness of the con-control rod movement and compliance trol rod withdrawal sequence with the prescribed control rod input to the RWM computer pattern are verified by a second shall be verified, licensed operator or technically qualified member of the station technical staff.
- 3. Otherwise, with the RWM inoperable, control rod withdrawal movement shall not be permitted except by full scram.
Control rods may be moved, under administrative control to permit testing associated with demonstrating operability of the RWM.
- c. Deleted,
- c. When required, the presence of the second licensed operator or technically qualified member of the station technical staff to verify the following of the correct rod program shall be verified and recorded.
1 Amendment No. 33, 43, 47, 153
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PBAPS UNIT 3 s
3.3.A and 4.3.A BASES (Cont'd)
Studies have been made which compare experimental criticals with calculated criticals.
These studies have shown that actual criticals can be predicted within a given tolerance band.
For gadolinia cores the additional margin i
required due to control cell material manufacturing tolerances and calculational uncertainties has experimentally be.en determined to be 0.38% ok/k.
When this additional margin is demonstrates, it assures that the reactivity control requirement is met.
2.
Reactivity Margin - Inoperable Control Rods Specification 3.3.A.2 requires that a rod be taken out of service if it cannot be moved with drive pressure.
If the rod is fully inserted and then disarmed i
electrically *, it is in a safe position of maximum contribution to shut down reactivity.
If it is disarmed electrically in a non-fully inserted position, that position shall be consistent with the shutdown reactivity limitation stated in Specification 3.3.A.1.
This assures that the core can be shutdown at all times with the remaining control rods assuming the strongest operable control rod does not insert.
Inoperable bypassed rods will be limited within any group to not more than one control rod of a (5x5) twenty-five control rod array.
Also if damage within the control rod drive mechanitm and in particular, cracks in drive internal housings, cannot be ruled out, then a generic problem affec-ting a number of drives cannot be ruled out.
Circumferential cracks resulting from stress assisted intergranular corrosion have occurred in the collet hous-ing of drives at several BWRs.
This type of cracking could occur in a number of drives and if the cracks propagated until severance of the collet housing occurred, scram could be prevented in the affected rods.
Limiting the period of operation with a potentially severed rod and requiring increased surveil-lance after detecting one stuck rod will assure that the reactor will not be operated with a large number of rods with failed collet housings.
- To disarm the drive electrically, four Amphenol type plug connectors are removed from the drive insert and withdrawal solenoids rendering the rod incapable of withdrawal.
This procedure is equivalent to valving out the drive and is preferred because, in this condition, drive water cools and minimizes crud accumulation in the drive.
Electrical disarming does not eliminate position indication.
l Amendment No.153
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5 PBAPS UNIT 3 3.3 and 4.3 BASES (Cont'd) 8.
Control Rods 1.
Control rod dropout accidents as discussed in the FSAR can lead to significant core damage.
If coupling integrity is maintained, the possibility of a rod drop-out accident is eliminated.
The overtravel position feature provides a positive check as only uncoupled drives may reach this position.
Neutron instrumentation response to rod movement provides a verification that the rod is following its drive.
Absence of such response to drive movement could indicate an uncoupled condition.
Rod position indication is required for proper function of the rod worth minimizer (RWM).
2.
The control rod housing support restricts the outward movement of a control rod to less than 3 inches in the extremely remote event of a housing failure.
The amount of reactivity which could be added by this small amount of rod with-drawal, which is less than a normal single withdrawal increment, will not con-tribute to any damage to the primary coolant system.
The design basis is given in subsection 3.5.2 of the FSAR and the safety evaluation is given in subsection 3.5.4.
This support is not required if the reactor coolant system is at atmos-pheric pressure since there would then be no driving force to rapidly eject a drive housing.
Additionally, the support is not required if all control rods are fully inserted and if an adequate shutdown margin with one control rod with-drawn has been demonstrated, since the reactor would remain subcritical even in the event of complete ejection of the strongest control rod.
3.
The Rod Worth Minimizer (RWM) restricts withdrawals and insertions of control rods to prespecified sequences.
All patterns associated with these restrictions have the characteristic that, assuming the worst single deviation from the restrictions, the drop of any control rod from the fully inserted position to the position of the control rod drive would not cause the reactor to sustain a power excursion resulting in the peak enthalpy of any pellet exceeding 280 calories per gram.
An enthalpy of 280 calories per gram is well below the level at which rapid fuel dispersal could occur (i.e., 425 calories per gram).
Primary system damage in this accident is not possible unless a significant amount of fuel is rapidly dispersed.
Ref. Sections 3.6.6, 14.6.2 and 7.16.3.3 of the FSAR, NED0-10527 and supplements thereto, and NEDE-24011-P-A.
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1 Amendment No. 18, #1, 67,153
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PBAPS UNIT 3 3.3.B and 4.3.B BASES (Cont'd)
In performing the function described above, the RWM is not needed to impose any restrictions at core power levels in excess of 10 percent of rated power.
Mate-rial in the cited references shows that it is impossible to reach 280 calories per gram in the event of a control rod drop occurring at a power level greater than 10 percent, regardless of the rod pattern.
This is true for all normal and l
abnormal patterns, including those which maximize individual control rod worth.
I The Rod Worth Minimizer provides automatic supervision to assure that out-of-l sequence control rods will not be withdrawn or inserted; i.e., the RWM system limits operator deviations from planned control rod movement.
The RWM is an important system for minimizing the consequences of an RDA below 10% power.
The RWM is therefore required to be operable for all but one startup per year before the first twelve control rods are fully withdrawn.
One startup per year before the first twelve control rods are fully withdrawn will be permitted with the RWM inoperable provided control rod movement and compliance with the pre-scribed control rod pattern are verified by a second licensed operator or tech-nically qualified member of the station technical staff.
The function of the RWM makes it unnecessary to specify a license limit on rod worth to preclude unacceptable consequences in the event of a control rod drop.
At power levels below 10 percent of rated, the RWM forces adherence to acceptable rod patterns.
Above 10 percent of rated power, no constraint on rod pattern is required to assure that rod drop accident consequences are acceptable.
Control rod pattern constraints above 10 percent of rated power are imposed by power distribution l
requirements as defined in Section 3.5/4.5 of the Technical Specifications.
4.
The Source Range Monitor (SRM) system performs no automatic safety system function; i.e., it has no scram function.
It does provide the operator with a visual indication of neutron level.
The consequences of reactivity accidents are functions of the initial neutron flux.
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Amendment No. 33, 41, 43, 153
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