U-602179, Provides Info on Results of Util Review of Functional Design Criteria for post-accident Neutron Monitoring
| ML20056H217 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 08/31/1993 |
| From: | Phares R ILLINOIS POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 U-602179, NUDOCS 9309090009 | |
| Download: ML20056H217 (6) | |
Text
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Enors Power Company Cl.nton Power Station i
P.O Bor 678 Chnton, IL 61727 Ter 217 935-8881 ILLINOIS POWER EZ2pg,gw 1 A.120 August 31, 1993 Docket No. 50-461 Document Control Desk Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Clinton Power Station Neutron Monitoring System Regulatory Guide 1.97 Compliance Dear Sir; On June 18,1993 (Letter U-602149) Illinois Power (IP) committed to review the Clinton Power Station (CPS) neutron flux monitoring instrumentation against the functional design criteria identified in the BWR Owners' Group (BWROG) topical report NEDO-31558, " Position on NRC Regulatory Guide 1.97, Revision 3, Requirements for Post-Accident Neutron Monitoring System." The topical report proposes alternate criteria for an acceptable Neutron Monitoring System (NMS) instrumentation design in lieu of the category I criteria stated in Regulatory Guide 1.97. Attachment I to this letter provides the results oilP's review.
In summary, and as documented in the attachment to this letter, the CPS NMS fully complies with the alternate design criteria identified in the topical report.
Sincerely yours, D h.
he Richard F. Phares Director-Licensing TAB /nis Attachment NRC Clinton Licensing Project Manager ec:
NRC Resident Oflice, V-690 Regional Administrator, Region III, USNRC Illinois Department of Nuclear Safety (g
);
9309090009 930831 e
PDR ADOCK 05000461 p
PDR g
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i to U-602179 Page1 of5 Review of Functional Design Criteria for Post-Accident Neutron Monitoring at Clinton Power Station 1
The BWROG Topical Report, NEDO-31558, defined and justified alternate post-accident design requirements for the NMS and compares these requirements to the Category 1 i
requirements in Regulatory Guide 1.97. Each of the alternate design criteria is listed below' j
(in the order that they are addressed in the topical report), and for each criterion an evaluation 1
of the existing CPS NMS instrumentation against that criterion is provided. As stated in the topical report, the scope of the criteria is limited to post-accident conditions.
L ELnge i
Alternate Requirement:
1 to 100%
CPS Capability:
The CPS average power range monitors (APRM) have a range l
which extends from 0 to 100% reactor power. In addition, the intermediate range monitors (IRM) have a range of 0.001 to 40% thus providing overlap with the APRMs. Therefore, the CPS NMS meets the alternate criteria for system indication -
range.
I 2.
Aggu_rtcy i
Alternate Requirement:
- 2% of rated power i
+
]
CPS Capability:
CPS procedure 9431.12, Average Power Range Monitor (APRM) Channel Calibration, provides for APRM channel calibration at least once 1
every 6 months in accordance with the CPS Technical Specifications. In addition, CPS Procedure 9431.60, Average Power Range Monitor (APRM) Gain Adjustment, provides guidance for a weekly APRM gain adjustment also in accordance with the CPS Technical Specifications.
The weekly adjustment verifies the APRMs are accurate to
- 2% rated thermal power based on the power values calculated by a heat balance during Operational Condition I when thermal power is' greater than or equal to 25% of rated thermal power. The post-accident APRM accuracy, therefore, meets the alternate criteria with the existing APRM equipment.
3.
Response Characteristig Alternate Requirement:
5 second/10% change CPS Capability:
The CPS power range monitors are des.gned such that with the neutron flux in the vicinity of the LPRM detectors increasing at t rate.which i
j corresponds to a power increase of 4000% power per second on an average basis, the trip contacts of the APRM system complete trip contact motion (openmg and closing) within 20 milliseconds after the average flux reaches the scram trip level. This is more
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t than adequate to meet the response characteristic requirement as stated in NEDO-31558.
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4.
Equipment Oualification i
Alternate Requirement:
Operate in ATWS Environment CPS Capability:
Section 4.0 of NEDO-31558 describes the equipment i
environment for those events where the NMS is important to the operator. As stated
{
in that section, the ATWS events establish the most limiting environmental conditional during which the NMS operation is needed. However, the most severe environmental j
impact occurs as a result of a large break Loss of Coolant Accident (LOCA) with
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failure of one division oflow pressure Emergency Core Cooling System or from a loss i
of drywell coolers and a failure to scram.
General Electric (GE) BWR Requirements Document 22A6926, BWR Equipment f
Environmental Interface Data, provides environmental limits for various plant t
conditions under normal, abnormal and accident environments.
GE Data Sheet l
22A6926AA, provides the CPS specific list of equipment identifying applicable
{
locations, limits and conditions from the requirements document. (These requirements have also been incorporated into CPS USAR Table 3.11-5). The CPS NMS design requirements include the postulated environmental conditions for both a large break LOCA and a loss of HVAC. These environmental conditions bound the ATWS environments expected and therefore, CPS meets the alternate criteria with existing i
APIBi equipment.
l 5.
Function Time i
Alternate Requirement:
Ihour l
CPS Capability:
As described above, the GE BWR Requirements Document for
-i the standard BWR/6, 22A6926, prosides environmental limits for various plant conditions under normal, abnormal and accident environments. As noted on the GE Data Sheet,22A6926AA, the function times for the CPS NMS meet or exceed one hour for all scenarios including the ATWS events. The CPS NMS meets or exceeds the alternate requirement for function time with the existing equipment.
6.
Seismic Oualification Alternate Requirement:
Seismic qualification not required CPS Capability:
The CPS NMS equipment which provides automatic trip functions have been seismically qualified to assure that the seismic event does not prevent the automatic trip function. All devices and circuitry from sensor to trip output are classified as Seismic Category I in accordance with Regulatory Guide 1.29.
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Page 3 of 5 t
The remainder of the Nh1S equipment has generally not been seismically qualified.
l Therefore, existing CPS NMS equipment meets or exceeds the alternate criteria.
7.
Redundancy and Segration j
Alternate Requirement:
Redundancy to assure reliability l
l CPS Capability:
The CPS APRM system is comprised of four identical, but l
independent channels. The independence and redundancy incorporated into the design 4
of the APRM system is consistent with the safety design bases of the reactor i
protection system. The existing CPS NMS meets the redundancy and separation requirement.
8.
Power Sourens
]
Alternate Requirement:
Unintermptable and reliable power sources CPS Capability:
The four redundant APRM channels are powered from four l
independent and reliable Nuclear System Protection System (NSPS) Class IE uninterruptible power supplies. These sources provide the high voltage for the Local Power Range Monitors (LPRhts), logic power and panel display power in each i
channel. All recorders are powered from a single, independent, non-divisional AC bus.
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Neither the four redundant NSPS uninterruptable power supply buses nor the non-divisional bus powering the recorders are lost due to load shedding or similar schemes, I
and a single failure will not result in the loss of all channels. Therefore, the CPS NMS a
power supplies meet the alternate requirement with the existing power sources.
9.
Channel Availability Alternate Requirement:
Available prior to accident d
CPS Capability:
All four CPS APRM channels are required to be operable j
during power operation in accordance with the CPS Technical Specifications.
Therefore, the CPS NMS existing design meets this criteria.
10.
QualityAssurance Alternate Requirement:
Limited QA requirements based on Generic Letter 85-06 i
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f Attachment I to U-602179 l
Page 4 of 5 l
CPS Capability:
All CPS NMS equipment and cabling, with the exception of l
Intermediate Range Monitor (IRM) and Source Range hionitor (SRM) drive motors, are classified as safety-related. Illinois Power has documented CPS compliance with i
the guidance provided in Generic Letter 85-06 for nonsafety-related equipment. CPS l
is, therefore, in full compliance with the alternate criteria.
11.
Display and Recording Alternate Requirement:
Continuous recording
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CPS Capability:
Four dual-pen chart reccrders plot the average power level output from each APRM channel when selected for the APRM mode. - Each recorder is shared with the IRMs and will plot IRM channel output when in the IRM mode. In l
addition, the CPS Display Control System provides APRM channel level indication on j
a CRT screen located in the main control room. Four dual indicating bar graphs indicate the average power level output of each APRM channel on a 0 to 125% scale.
Each bar graph also indicates the flow biased upscale alarm setpoint for the associated l
channel. Digital indication of each APRM channel average power level and alarm setpoint is displayed above each bar graph. Therefore, the CPS design satisfies this
[
l requirement.
l E_qt ipment Identification 12.
a Altemate Requirement:
Identify in accordance with CRDR I
1 CPS Capability:
As stated in a Safety Evaluation Report dated June 8,1990 the NRC staff concluded that CPS has met all the requirements of Supplement I to NUREG 0737 and that the scope of the Detailed Control Room Design Review (DCRDR) performed at CPS included all Regulatory Guide 1.97 instrumentation. The CPS NMS recorders are clearly marked consistent with the results of the DCRDR and therefore meet the alternate criteria.
13.
Interfaces Alternate Requirement:
No interference with RPS trip functions CPS Capability:
Where electrical interfaces between class IE (or associated Class IE) and non-class 1E circuits, or between Class IE (or associated Class 1E)
)
circuits of different divisions cannot be avoided, isolation devices are used, except wherejustified by analysis. The CPS NMS is equipped with isolation devices between the Non-Class lE and Class lE ponions of the system. In addition, the NMS logics i
are arranged so that failure of any one logic cannot prevent the initiation of a high j
1 neutron flux scram. There are four NMS logics associated the RPS. The existing CPS NMS design therefore fulfills the alternate requirement.
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Service. Test and Calibration Alternate Requirement:
Establish in plant procedures i
CPS Capability:
CPS has developed procedures to ensure maintenance of the NMS. These procedures are written to ensure compliance with scram and rod block requirements. Recorder verification is included in the APRhi and SRhi channel calibrations. As noted above, CPS procedures provide for semiannual calibration of the APRh1 channels and weekly APRhi gain adjustments which ensure that overall l
loop accuracy requirements are met. CPS procedures, therefore, meet the specified alternate requirement.
15.
Human Factors Alternate Requirement:
Incorporate human factors engineering (HFE) principles i
CPS Capability:
As stated above, CPS has met all the requirements of Supplement I to NUREG 0737 including the NhfS instrumentation. As documented j
in the CPS DCRDR, the NhiS is designed using good HFE practices. Therefore, the CPS Nhis meets the alternate requirement with the existing equipment.
16.
Direct Measuremenj 1
Alternate Requirement:
Direct measurement ofneutron flux CPS Capability:
The CPS NhtS is equipped with fission chamber type detectors which when placed in the reactor core, provide a signal proportional to the intensity of the neutron fiux.
The CPS NhiS, therefore, meets the requirement for direct t
measurement of the neutron flux.
In summary, Illinois Power has evaluated the CPS NhiS design against the alternate requirements for a BWR Nh1S as prescribed in NEDO-31558. The CPS NhiS meets or exceeds the alternate criteria identified in the topical repon.
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