ML20151W539
| ML20151W539 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 04/28/1988 |
| From: | Cesare J SYSTEM ENERGY RESOURCES, INC. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| ACEM-88-0083, ACEM-88-83, NUDOCS 8805030421 | |
| Download: ML20151W539 (24) | |
Text
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j EVETEM ENERGY REEOUNCEE, INC.
JDif 4 G CEW4. J?
y%_q April 28, 1988 U. S. Nuclear Regulatory Comission Washington, D. C.
20555 Attention:
Document Control Desk Gentlemen:
SUBJECT:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 GGNS Plant Specific Design Evaluation for NED0 31558 AECM-88/0083 On April 1.1988 the BWR Owners Group submitted the Licensing Topical Report; "Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post-Accident Neutron Monitoring System" (NED0 31558). This Topical Report provides an event analysis of the neutron monitoring system functions for post accident use. The results of this analysis provided alternate neutron monitoring functional design criteria for Reg Guide 1.97.
As discussed in the Topical Report submittal cover letter (BWROG-8897/BWR1), the BWR Owners Group requested NRC priority review of the report considering the current licensing status of several BWR utilities for resolving this issue.
The Grand Gulf Nuclear Station (GGNS) Operating License Condition 2.C.(36) requires installation or upgrade of the neutron monitoring system to meet R.G. 1.97 by startup from the third refueling outage. This outage is currently scheduled to begin in February 1989. As discussed in letter AECM-88/0051 dated March 11, 1988, System Energy Resources, Inc. (SERI) is pursuing a multidirectional approach for addressing this license condition.
NRC review and evaluation of the BWR Owners Group Topical Report is a key consideration in determining the future neutron monitoring system direction for GGNS.
Since the functional design criteria of the Topical Report references the need to have a plant specific evaluation, SERI is submitting the GGNS neutron monitoring system design evaluation as it relates to the Topical Report (Attachment 1). To facilitate NRC review, the section numbering in corresponds to the design criteria sections of the Topical Report.
8805030421 880428 PDR ADOCK 05000416 OO P
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J16AECM88041301 - 1
AECM-88/0083 Page 2 Based on the implementation schedule currently imposed by GGNS Operating License 2.C(36), SERI requests that the NRC review of the Topical Report and GGNS plant specific design evaluations be performed expeditiously. As discussed with NRR Staff personnel on April 25, 1988, we request that an NRC Topical Report review schedule be provided to SERI by May 6, 1988 in order to allow SERI to continue further planning and scheduling on this matter to support resolution by the GGNS third refueling outage.
Yours truly,
\\
i 00K:bms Attachment cc: Mr. T. H. Cloninger (w/a)
Mr. R. B. McGehee (w/a))
Mr. N. S. Reynolds (w/a Mr. H. L. Thomas (w/o)'
Mr. R. C. Butcher (w/a) l Dr. J. Nelson Grace, Regional Administrator (w/a)
U. 5. Nuclear Regulatory Commission i
Region II l
101 Marietta St., N. W., Suite 2900 Atlanta, Georgia 30323 Mr. L. L. Kintner, Project Manager (w/a)
Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Connission Mail Stop 14820 Washington, D.C.
20555 f
J16AECM88041301 - 2
i
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~ Attcchment.1 4
to AECM 88/0083 17 GGNS Neutron Monitoring Plant Specific Design Evaluation (NEDO-31558)
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Introduction This attachment provides plant specific information relative to the capabilities of the existing Neutron Monitoring System-(NMS) at Grand Gulf as it applies to the alternative design requirements stated in NEDO-31558 (Reference 1), "Position o'n NRC Regulatory Guide 1.97, Revision 3 Requirements fo'r Post Accident Neutron Monitoring System".
-The topics of discussion in the following sections of this attachment correspond to subsections 5.2.1 through 5.3 of NED0-31558.
To facilitate i
understanding of the information presented by this attachment, the individual NEDO-31558 subsection headings and requirements are restated followed by a brief discussion of existing capabilities of the GGNS NMS. The basis for the alternative requirements is not restated as this information is provided in NEDO-31558.
The information provided under each subsection primarily applies to the APRM subsystem. However, when appropriate, information is also being provided for the IRM subsystem to show its capability to provide a backup cr confirmatory support function to the APRMs when at the lower end of their operating range (i.e.,
i overlap. region).
'Since the position of NEDO-31558 is based on the operators' actions stated in the emergency operating procedures (utilization of the NMS for these actions) an initial discussion of the applicable GGNS Emergency Procedures (EPs) and their similarities / differences to the generic BWR Emergency Procedure Guidelines (EPGs) is as follows.
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J GGNS Emergency Procedure (EP) Overview r
The GGNS EPs were developed directly free heviaion 3I of the EPGs.
Because: core power (neutron finx) is the parameter of interest, discussion will
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- be restricted -to those EPs that are concerned with maintaining and controlling this parameter. At Grand Gulf the EPs related to core power are; EP-2, "RPV
. Control" and EP-14,'"Level / Power Control".
Consistent with the intent of the EPGs, the RPV Control procedure provides the operator with direction to control reactor power under conditions which may not necessarily require boron injection while the Level / Power Control EP provides the necessary direction to control power under conditions where boron injection is required. The entry conditions ~for EP-2 provide plant specific values for RPV pressure, level, power, and drywell pressure. The scram / power entry condition encompasses the condition where the operator may not be able to determine reactor power.
The bases document for the EPGs discusses the fact that loss of electrical power to the APRMs does not, by itseli, necessarily mean that reactor power cannot be determined. The ensuing discussion provided by the bases document further supports the variables / methods used to determine reactor power that were specified in NED0-31558 Section 6.3.
The general guidance provided by EP-2 regarding the control of reactor power is as follows:
If all control rods are not inserted to or beyond position 02 (Maximum o
Suberitical Banked Withdrawal position) and reactor power is less than the downscale trip of 4% then in concurrence, attempt to insert all control rods to or beyond position 02 using all possible methods and if required initiate boron injection using both SLC pumps prior to the suppression pool reaching 110*F (Boron Injection Initiation Temperature).
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o If all control rods are not inserted to or beyond positice 02 and either power cannot be determined or power is greater than 4%, then initiate ARI/RPT, and concurrently, attempt to insert control rods by all possible methods, and if required inject boron using both SLC pumps prior to suppression pool temperature reaching 110*F.
o If at any time during the performance of EP-2, all control rods are inserted to or beyond position 02 then terminate boron injection, enter the scram Off Normal Event Procedure (0NEP), and exit the power control logic leg of EP-2.
o If while performing the above actions the reactor is determined to be shutdown and no boron has been in ected then exit the power control s
logic leg of EP-2 and ente the scram ONEP.
The injectten of boron into the 5FV for the above listed actions is instituted by a limiting suppression pool temperature of 110*F (Suppression Pool Temperature is a Category 1 variable as defined in RG 1.97).
Action is conservatively taken befor< reaching this temperature to preclude the possibility of compromising the integrity of the containment from a forced emergency depressurization at high power levels.
As stated in the.EPs, once boron has been injected into the RPV the "hot" or "cold" shutdown boron concentration (in ppm) must be determined by cheulcal analyses.
Once boron has been injected, tbe operator in instructed to enter EP-14 and execute it concurrently with EP 2 for level / power control. The actions required of the operator when performing EP-14 are those actions which will ensure that the hot shutdown boron weight is injected while minimizing the energy being discharged into the containment.
Concurrently, EP-2 assures that adequate boron is injected into the vessel to achieve and maintain cold shutdown conditions. _
5.2.1 Range Alternate Requirement:
1 to 100% (GGNS downscale alarm is 4%)
RG 1.97 Requirement:
10 6% to 100%
The operating range associated with the APRM subsystem at GGNS is 1 to 100% core thermal power (approximately 2.8 X 1012nv to 2.8 X 1014nv). This range satisfies the alternate requirement stated above.
In addition, the GGNS IRM instrumentation has en operating range of
.'.0 4% to at least 15% power (approximately 1 X 10snv to 1.5 X M83nv).
5.2.2 Accuracy Alternate Requirement:
12% of Rated Power RG 1.97 Requirement:
None stated The loop accuracy of the GGNS APR:t subsystem is 12% (for normal operations at rated power) based on G.E. setpoint methodology calculations.
Loop accuracy of the APRM subsystem at power levels near the APRM downscale trip will have to be determined. The accuracy at this lower power level may vary from tne alternate requirement specified by NEDO 31558. To maintain this degree of accuracy the LPRM subsystem is calibrated every 1000 MWD /T using the TIP subsystem. Whenever power is 2 25%, each APRM channe) is checked a minimum of once a week against
[
power as determined by a heat balance and the APRM channel is adjusted as required to produce a deviation of no more than 2% of rated power.
Due to the measures taken to assure loop accuracy the APRM subsystem i
I meets the alternate requirements as stated in NEDO-31558.
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'5.2.3 Response Characteristic Alternate ~Requirecent:
5 Sec/10% Change a
RG 1.97 Requirement:.
None Specified For the.GGNS APRM subsystem this characteristic has been
'previously stated in NED0-31558.
5.2.4 Equipment Qualification Alternate Requirement:
Operate in ATWS Environment i
RG 1.97 Requirement:
RG 1.89 and 1.100 GGNS Expected Environmental Conditions From ATWS Event As discussed in NEDO-31558, the bounding events for determination of design basis requirements for the NMS as it applies to RG 1.97 are the lesser ATWS events.
Lesser ATWS events for the purposes of this attachment are defined as those ATWS events for wnich partial control rod insertion occurs or the plant is not 1"olated from the main condenser. As discussed in NEDO-31558,'the event which is selected to be bounding for tids category of events is "Inadvertent SRV opening with partial scram failure". This event; therefore, establishes the environmental conditions and function time requirements for the NMS as it applies to post accident event monitoring.
t The above identified event has been analfzed in NEDO-24222 (Reference 2) and the acalysis presented therein is determined to be bounding for GGHS. The analysis presented in NED0-24222 assumes a complete failure to scram (and ARI failure). Even though the NMS design basis requirement event discussed in NEDO-31558 assumes a partial scram failura, this event (complete failure to scram) environmentally encompasses the special case of partial scram failure and should yield a conservative (harsher conditions) environmental
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profile. Therefore, the following environmental profile is based on the base case of a complete failure to scram. The results of the NEDO-24222 analysis for this event show that the peak suppression pool temperature of 170*F and peak containment pressure of 7.5 psig are reached at 50 minutes into the event, indicative that the event produces a gradual increase in both parameters during the event.
If it is assumed that these same conditions translate to the conditions in the drywell, this now identifies the worst case conditions existing in the drywell during this event. No degradation of environmental conditions is expected to occur within areas of the Auxiliary Building during this event. The NED0-24222 analysis of this event also assumes the unlikely failure of the ARI system, which is currently installed at GGNS.
In cases whe.e ARI is accomplished, the maxircum suppression pool temperature would be limited to 155'F.
Other Environmental Conditions Even though the event for which neutron monitoring is required has been determined to be an ATVS, the operator may need to determine reactor power during certain design basis accident events. This is primarily due to the symptomatic operator actions required by the BWR EPGs and GGNS EPs.
1.
Large Break LOCA Environmental conditions rapidly degrade and the NMS equipment locatea in the drywell and containment would be exposed to very harsh conditions. Therefore, the function time for the neutron monitoring equipment would be limited. However, 'le actions required of the operator by the GGNE EPs regardles of whether the plant is saur.down would be virtually the same. As explained in paragraph five of Section 4 3.2.1 of NED0-31558 the operetor does not require use of the NMS for the pu.n..ses of boron injection, RPT, or to determine the need to lower water level since the operators main objective is to achieve some method of
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long term core cooling / submergence via the use of low pressure systems. For this reason a NMS failure for this event does not significantly affect operator response.
2.
Small Break LOCA The small break LOCA is the accident event for which operator actions from the NMS would be expected to be required for performance of the GGNS EPs. Direct operator interface with EP-2
.and the Containment Control EP may be necessary for a significant period of time due to the nature of the tvent. The rate of pressure rise inside the drywell is directly related to the siza of the break and therefore, the time to reach the drywell high pressure trip is dependent also on the size of the break. The environmental conditions inside the containment would be more severe than those associated with an ATWS, but less severe then those associated with the large break LOCA.
Once the reactor trip signal for high drywell pressure occurs, the operator actions would be to concurrently perform the
.immediate actions of the scram Off Normal Event Procedure (ONEP) and perform the actions as required in EP-2 and the containment control EP.
During performance of the immediate actions of the scram ONEP the IRMs are inserted into the core which would take apprcximately three minutes for full insertion if the IRMs were fully retracted (the integrated operating instructions at GGNS i
fully retracts and positions the IRM< on range three after the APRM's are above the downscale alarm).
EP-2 as mentioned in the introduction to this attachment would direct the operato:- to concurrently control RPV pressure, level and power. As discussed in 4.3.2.2 of NED0-31558 the operator completes EP actions related to power control as soon as the reactor is shutdown (if no boron has been injected) or RPIS indicates that all rods are to or beyond position 02.
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GGNS Environmental Design Considerations
'The following information provided for environmenta'i qualification
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is-based on either:-
y a) a review of the'GGNS Environmental Qualification Files.or, b) a representation by General Flucttic of qualification testing previously performed for GGNS, or testing conducted for other similar BW3 designs that is expected to be applicable to GGNS.
Since the APRM and IRM neutron monitoring subsystems are not currently required for post accident operation, the qualification files and GE qualification data would have to be further evaluar.ed for overall 10CFR50.49 qualification acceptability elong with a complete review of the post accident environmental conditions. SERI does not currently retain this environmental qualification data and because of this it would have to be obtained from GE. Therefore, the following information represents what is considered to be that instrumentation which can be qualified based on currently existing data.
LPRM/APRM As a minimum the components of the LPRM/APRM subsystem located within the drywell/ containment will survive environmentally undet the following conditions:
Temp (*F)
Press (psig)
Humidity %
330 30 All Steam i
In addition, the equipment located within the Auxiliary Building is designed to operatt under the accident profiles of their respective locations and since the equipment located within the cor. trol room is located in a mild environment it is considered to te available.
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r The following tables represent the sources of documentation:
DryweII/ Containment:
QUALIFIABLE QUALIFIABLE PER IER NOT QUALIFIED __l GGNS FILE GE FILES l
l l
1 l Detector Assembly X
l l
l l Cabling X
l l
l Penetrations l
l l
___l X
Auxiliary Building,:
QUALIFIABLE QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED
-l 1
l l
I l Cabling l
X l
l l
Control Building:
l (Instrument l
l l Monitors Drawers) l Mild Environment; I
l l No Qualification Required.
l l
l l Recordcrs From the above tabulated data it can be seen that the APRM subsystem is fully capab,le of surviving the mildiv degraded environmental conditions that would be espected under the ATWS event described earlier and for all practical purposes would survive under the small break LOCA profile even though NMS is not necessary for this event. Therefore, the APRM subsystem exceeds the alternate requirement for environmental availability as stated in NEDO-31558.
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t' IRMs As a minimum, the components (with the exceptions of the drives / motor modules) of the IRl' subsystem which are located within the drywell/ containment are capable of operating within, and surviving, the following environmental conditions.
Temp (*F)
Press (psig)
Humidity %
330*F 30 All Steam In addition, the components located within the Auxiliary Building are designed to operate under the accident jcofiles of their respective equipment rooms / locations. The equipment located within the control room is in a mild environment and is considered to be available.
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The following tables represent the sources of documentation:
Drywell/ Containment:
QUALIFIABLE QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED
_ l l
l l
I l Detector Assembly X
l
[
l I
l Cabling X
l 1
I l Penetrations X
l l
l l Drives / Motor Modules l l
l X
l i
Auxiliary Building:
QUALIFIADLE QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED I
l l
l l
l Voltage Preamps X
l l
l l Cablina I
X l
l l
Control Building:
~~
l' (Instrument l l
l Monitors' Drawers) l Mild Environment; 1
l l No Qualification Required.
l Recorders l
l The availability of the IRM subsystem following a small break LOCA (due to initial insertion of the IRMs upon the high drywell
_ pressure scram s gnal) is dependent upon the ramp rate of environmental i
~ degradation contingent upon the break size.
NEDU-31558 gives representative values for these conditions and since these conditions are similar to those expected for the ATWS design basis requirement event for NMS there is a high liklihood that the IRM subsystem will be available up to the point that EP actions for power control are satisfied.
From the above tabulated data it can be seen that the IRM subsystem (with the exception of the IRM drive / motor modules), would be available to provide information in the control room for both ATWS l
and small break accidents.
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5.2.5 Function Time Alternate Requirement:
1 Hour RG 1.97' Requirement:
None Specified.
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'From the results of the ATWS event discussed'in.the previous i
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section and presented in NEDO-24222, it is evident reactor power has been reduced to essentially 0% at approximately thirty. minutes into the event. Grand Gulf's EPs specify that once liquid boron has been injected, 'the shutdown boron concentration in the reactor coolant must be determined by chemical analysis unless the reactor is determined to be shutdown with all control rods at or beyond position 02.
From this point on the NMS availability to the operator is appropriate as en enhancement; however, not as a requirement. The NMS will not be necessary to confirm reactor shutdown or that the reactor remains shutdown, as this will be done by determining the proper shutdewn I
weight of boron using chemical analysis and ultimately through insertion of all rods to or beyond position 02 (Maximum Suberitical Banked Withdrawal position). Based on the above discussion and the r
information presented in the preceeding scetion, the NMS meets the alternate requirement specified above.
5.2.6 Seismic Qualification Alternata Requirement:
Seismic qualification not required RG 1.97 Requirement:
Seismically qualify Cat 1 equipment as important to safety per RG 1.100 and IEEE-344 Since the event which has been determined to set the design basis requirements for the 7MS is an ATWS event, seismic requirements for the NMS should be consistent with the ATVS rule (10CFR50.62). This I
rule specifies ATWS environnental conditions which do not require seismic qualifiestion.
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However,-the APRMs and.certain portions of the IRM subsystem are
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designed to operate during the design basis earthquake (DBE). This l
capability exceeds the alternate l requirement of NEDO-31558.
The'following APRM and IRM' tables represent the methed/ source of seismic qualification documentation that supports the above. This information is based on either:
I a) Information presently contained in the GGNS seismic qualification files or b) supporting information contained in the GE seismic qualification files.
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LPRMS/APRMS Dryvell/ Containment:
QUALIFIED QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED I
l l
l l
l Detector Assembly X
l l
l l Cable Trays X
l 1
l l Penetrations l
X l
l
,,)
Auxiliary Building:
QUALIFIED QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED l
l l
l l
l Cable Trays l
X l
l l
Control Building:
QUALIFIED QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED l
(Instrument l l
l l
l Monitors Drawers)
X l
1 I
l Recorders l
l l
X*
l
- The IRM/APRM recorders are Bailey Model 771 series. This particular recorder is not seismically qualified; however, this model of recorder (Bailey, 771 series) has been qualified previously for use in other GGNS applications.
Based on the above seismic data, the LPRM/APRM subsystem would meet the seismic qualification requirements of RG 1.97.
The APRM system otherwise exceeds the alternate requirement specified.
1 1 -
IRMs Drywell/ Containment:
QUALIFIED QlMLIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED I
I I
I 1
l Detector Assembly X
1 l
l l Cable Trays X
l l
l l Penetrations X
l l
l l Drives / Motor Modules l l
l X
l Auxiliary Building:
QUALIFIED QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED l
l I
I l
l Voltage Preamps X
l l
l l_ Cable Trays l
X l
l l
Control Building:
QUALIFIED QUALIFIABLE PER PER NOT GGNS FILE GE FILES QUALIFIED l~
(Instrumentl l
l l
j, Monitors Drawers)
X l
l l
l Recorders l
l l
X*
l
- The IRM/APRM recorders are Bailey Model 771 s-ries.
This particular recorder is not seismically qualified; however, this model of recorder (Bailey, 771 series) has been qualified previously for use in other applications / systems.
Based on the above seismic data, the IRM subsystem would meet the seismic qualification requirements of RG 1.97 except in the case of a seismic event that disabled the eight IRM drives and motors.
Therefore, for all cases except for motor and drive disablement, the IRMs would also be available to provide additional supporting information to the operator af ter a seismic event for monitoring power at or around the 4% downscale alarm.
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s4 5.2.7 Redundancy _and Separation Alternate Requirement:
Redundancy to Assure Reliability RG 1.97 Requirement:
Redundant in Division Meeting RU 1.75 The APRM subsystem consists of eight independent channels, each channel consisting of inputs from up to twenty-two LPRM detectors and the necessary signal conditioning equipment, to provide an output signal directly reflecting average powet in the cora. This output signal is then utilized to provide reactor trip signals, alarms, and indication. The eight channels are divided into four separate divisions with each division consisting of two APRM channels.
Because of the redundancy in detector inputs (only 14 required for operability per GGNS Technical Specifications) per channel, the application of power and equipment separation, and the total number of channels, the APRM subsystem satisfies the alternate redundancy and separation criteria. The methods used for identifying power cables, signal cables, and cable trays as scfety related components and the identification scheme used to distinguish between redundant cable, cable trsys, and instrument panels is in accordance with regulatory guide 1.75.
The IRM subsystem is near identical in design to the APRM subsystem with respect to redundancy (8 channels) and separation, f
5.2.8 Power Sources
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Alternate Requirement:
Uninterruptable and Reliable Power Sources RG 1.97 Requirement:
Standby Power Source (RG 1.32)
The four divisions of the APRM subsystem are supplied UPS power from four separate inverters. The normal power supply is from the associated Division 1 or 2 ESF bus with backup power supplied from the station batteries. The recorders located on the operators control console are supplied power from a separate UPS power source. This arrangement of power sources for the APRM subsystem satisfies the alternate requirement specified above..
The IRMs are afforded with the same divisional arrangement as the APRM subsystem and likewise are supplied UPS power from four separate
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inverters.
The IRM subsystem shares the same recorders as the APRM subsystem and therefore, the recorder power is as already specified.
The IRM drive motors and their control logic circuits are not supplied with UPS power.
I 5.2.9 Channel Availability Alternate Requirement:
Available Prior to Accident RG 1.97 Requirement:
Available Prior to Accident As discussed in NEDO-31558, the power range instrumentation is j
available and in service while the slant is operating; therefore, the existing design satisfies this requirement.
i 5.2.10 Quality Assurance Alternate Requirement:
Limited QA Requirements Basec on Gcnerie Letter 85-06 (Reference 3) l RG 1.97 Requirement:
Application of Specific Reg. Guides N
The entire APRM subsystem is safety related with the exception of the APRM recorders located on the operators control console, The APRM subsystem was constructed in accordance with 10CFR50 Appendix B.
As can be expected, the quality requirements associated with non-safety related equipment are less stringent than those associated with safety related components and for this reason the recorders were not designed, procured, and installed to the same quality level requirements as those associated with the remainder of the APRM equipment. Nonetheless, the i
eighteen criteria of Appendix B to 10CFR50 and the guidance provided, undec LRC Generic Letter 85-06 for non-safety related ATVS equipment have been fully satisfied by the procurement, design, installation, i
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F.p and ongoing operational quality assurance program, for the APM subsystem. Based on the above, the APRM subsystem satisfies the alternate requirement as stated above.
The IM subsystem shares the same safety class levels as does the APRM subsystem with the exception of the IRM drives / motor modules.
However, since the alternate requirements above specify compliance with Generic Letter 85-06 and all IRM equipment was installed to the requirements of 10CFR50 Appendix B, even though the drives / motor modules are non-safety class components, this requirement is satisfied by the IRH subsystem.
5.2.11 Display and Recording Alternate Requirement:
Continuous Recording RG 1.97 Requirement:
Continuous Recording Every NMS channel has continuous recording capability provided by strip chart recorders located on the operators control console. Also on th3 operators control console there are; downscale status indication (4% Core Thermal Power) for all APRM channels, LPRM downscale alarms. APRM downscale (4% CTP) annunciation, LPRM downscale annunciation, and four annunciators indicating inoperability of any channel.
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In addition, the downscale annunciator and status indicators for the APRM subsystem which are go/no-go indications assist the operator in his determination of whether power is above or below 4% relative to his actions in regards to the GGNS EPs (i.e., analeg monitoring capability could be construed as not required). On a complete reactor scram these indicators will come in instantaneously.
Based on this discussion, the requirement of NEDO-31558 is fully satisfied.
5.2.12 Equipment Identification Alternate Requirement:
Identify in Accordance with CRDR RG 1.97 Requirement:
Identify as Post-Accident Monitors The NMS recorders are all clearly marked and labeled by division, and signal input. These recorders are located on the central portion of the operators control console along with the other plant parameters which are of primary significance to the operator. Located between the four APRM recorders are the APRM status indicators, clearly identifying alarm levels (upscale /downscale/inop, etc.).
IRM channel status indication and annunciation is nearly identical to that of the APRMs.
This instrumentation was reviewed from a Human Factors standpoint for both useability and identification during performance of the DCRDR effort.
Based on the above, the identification of the equipment satisfies the requirement of NED0-31558, 5.2.13 Interfaces Alternate Requirement:
No Interference with RPS Trip Functions RG 1.97 Requirement:
Isolators to be used for Alternate Functions At Grand Gulf the non IE portions of the NMS are isolated and separated as required from the IE portions of the system. The NMS; therefore, satisfies the alternate requirement as stated above.. - _ _.
5.2.14 Service, Test, and Calibration Alternate Requirement:
Establish In Plant Precedures RG 1.97 Requirement:
Establish In Plant Procedures The NMS is tested and calibrated on the frequencies as specified in the GGNS Technical Specifications. Channel checks are generally performed every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and channel functionals performed weekly when the particular instrumentation is required to be in service (depends on plant operational conditions). The IRMs (trips, alarms, recorders, power supplies, regulators, etc.) are calibrated every 18 mon 's while n
these same functions on the APRM's are calibrated semi-annually.
On at least a weekly basis (with cc.e power 2 25%) each APRM is checked against core thermal power as indicated by heat balance and adjustments made when the APRM output deviates by more than 2% of rated power from power as indicated by the heat balance.
Every 1000 MWD /T the LPRM detectors are calibrated using the TIP system.
Plant section procedures cover the above described items.
The frequency of performance of these procedures is performed in the same manner as all other Technical Specification surveillance procedures.
Based on the above discussion, this requirement as specified in NEDO-31558 is satisfied.
5.2.15
.,9uman Factors Alternate Requirement:
Incorporate HFE Principles RG 1.97 Requirement:
Incorporate HFE Principles The DCRDR effort has been performed for the instrumentation and controls located on the operators control console.
Human factors engineering principles were incorporated into this review process; therefore, the NMS satisfies this criteria....
b
5.2.16 Direct Measurement Alternate Requirement:
Direct Measurement of Neutron Flux RG 1.97 Requirement:
Eirect Measurement of Neutron Flux The NMS utilizes miniature fission detectors and as such directly monitor neutron flux in the core. This criteria is satisfied.
5.3 Conclusion In all cases the APRM subsystem of the NMS meets or exceeds the alternate requirements established by NED0-31558 and in many cases complies with the requirements of RG 1.97.
Since the only operator actions that are predicated based on a known power level are those actions taken as a result of core power being above or below the APRM "Downscale Trip" value of 4%, the acceptance of a reduced monitoring range for RG 1.97 is considered justified. Otherwise, in the unlikely event that pewer cannot be determined, the operator has specific s
actions which may be performed to which the requirement to monitor power becomes unnecessary (although not undesirable) and neutron monitoring serves as an enhancement to the operator.
For the following reasons the APRM subsystem provides the operator with the capability and reliability to adequately determine reactor power in the region of the "Downscale Alarm",
o Acceptable Range Acceptable environmental and seismic survival o
Redundancy and number of channels Multiple al. arms and annunciation at do.nscale value o
c Multiple recorders Furthermore, since the function time of the IRH drive units is approximately 3 minutes (operator action to insert af ter a scram) it is very probable that under the events analyzed in this attschment and NED0-31558, the IRMs would be fully functional to provide any supportive monitoring capabilities to the APRMs for core power levels below 1%.
References:
1.
REDO-31558; Position on NRC Regulatory Guide 1.97, Revision 3 Requirements for Post Accident Neutron Monitoring System.
March 14, 1988, General Electric Company.
2.
NEDO-24222; Assessmcat of BWR Mitigation of ATWS, Volume 2 (NUREG 0460 Alternate No. 3), February 1981, General Electric Company.
3.
Generic Letter 85-06; Quality Assurance Guidance for ATWS Equipment That Ir Not Safety Related, April 16, 1985, Nuclear Regulatory Commission.
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