ML20217B889
| ML20217B889 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 10/01/1999 |
| From: | Hutton J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20217B893 | List: |
| References | |
| NUDOCS 9910130104 | |
| Download: ML20217B889 (7) | |
Text
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'I 10 CFR 50.90 f
PECO' NUCLEAR nco ** c---
965 Chesterbrook Boulevard
- A Unit of PECO Energy Wayne, PA 19087 5691-October 1,1999 Docket Nos. 50-277 50-278 License Nos. DPR43 DPR-Se
' U.S. Nuclear Regulatory Commission
' Attn: Document Control Desk Washington, DC 20555
Subject:
Peach Bottom Atomic Power Station, Units 2 and 3 Response to Request for Additional Information Related to License Change Request ECR 98-01802
Dear Sir:
l Attached is our response to your Request for Additional Information (RAI) dated, September 27,1999, regarding our request to install a digital Power Range Neutron Monitoring system and incorporate long-term, thermal-hydraulic stability solution hardware. to this letter provides a restatement of the RAI followed by our response.
If you have any questions, please contact us.
Very truly yours, JJ es A. Mutton, Jr.
7 rector-Licensing
Enclosures:
Affidavit, Attachment 1, Attachment 2 cc:
. H. J. Miller, Administrator, Region I, USNRC A. C. McMurtray, USNRC Senior Resident inspector, PBAPS '
R. R. Janati, Commonwealth of Pennsylvania
)
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1 0
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9910130104 991001
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PDR ADOCK 05000277' P
PDR l
b COMM NWEALTH OF PENNSYLVANIA:
ss COUNTYOF CHESTER i
1 l
J. J. Hagan, being first duly sworn, deposes and says j
That he is Senior Vice President of PECO Energy Company; the Applicant herein; that he has read the 4
enclosed response to the NRC Request for Additional Information dated September 27,1999, related to -
installation of a digital Power Range Neutron Monitoring system and incorporation of long-term, thermal-
' hydraulic stability solution hardware, and knows the contents thereof; and that the statements and
. matters set forth therein are true and correct to the best of his knowledge, information, and belief.
I Y
%w fice Pr ider t Subscribed and sworn to before me this [ day' of 1999.
/
"lfotary Public -
Notarial Seal Card A.Whiton, Notary W MyC.
E'xpi May
- = = =
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1 ATTACHMENT 1 I
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Response to Request for Additional Information Peach Bottom Atomic Power Station, Units 2 and 3 TS Table 3.3.1.1-1 Channes to Functions:
Question (1)
It is stated that 'APRM Inop" trip is changed to reflect NUMAC-PRNM and to delete minimum LPRM detector count from the trip, except alarm. Explain how and where it affected the proposed TS change (i.e., is this a change to TS Table 3.3.1.1 1 or a change to update the TS Bases?).
Response (1)
The information on minimum LPRM detector count was deleted from the TS Bases for the APRM-Inop Function of TS Table 3.3.1.1 1. This is equivalent to changes shown in the NUMAC PRNM LTR NEDC-32410P-A, page H-21. The TS Bases were revised to contain sufficient information to ensure an adequate basis for an understanding of the TS requirements based upon the NUMAC-PRNM design.
TS Table 3.3.1.1-1 Channes to Reauired Number of APRM Channels:
Question (1)
Increment inoperable APRM from 14 to 20 and new limit on maximum inoperable LPRMs per APRMs is not a proposed change on this table, is this a change to TS Table 3.3.1.1 1 or a change to update the TS bases?
Response (1)
The information on increasing the minimum number of operable LPRMs per APRM channel from 14 to 20 and information on the maximum number of LPRMs per APRM channel that may become inoperable and bypassed was added to the TS Bases discussion of the APRM Function of TS Table 3.3.1.1 1. This is equivalent to changes shown in the NUMAC PRNM NEDC-32410P-A, page H-15. The TS Bases were revised to contain sufficient Information to ensure an adequate basis for an understanding of the APRM TS requirements based upon the NUMAC PRNM design.
Question (2)
It is stated on page 3 that the setpoints and allowable values have been changed where Justified by the setpoint calculations and the Improved equipment performance specifications. Provide reference to NRC-approved setpoint methodology and performance specifications used for this calculation. Also on page 5 (last paragraph) it is stated that the allowable value for simulated thermal-high trip is based on engineering judgment. Which changed items in the table are based on calculations and which are based on engineering Judgment, and further explain the justification for using engineering judgment?
Response (2)
The setpoint methodology documented in NEDC-31336, " General Electric Instrumentation Setpoint
- Methodology,'is used to establish appropriate Allowable Values and setpoints for parameters that have
' analytical bases (which results in an Analytical Limit). NRC approval of NEDC-31336 is documented in a Safety Evaluation Report (SER) transmitted by letter from B. Boger (NRC) to D. Roare (GE) dated
- February 9,1993. For some parameters, there are no direct analytical bases, but equivalent design bases limiting values have been established. For those cases as well, the setpoint methodology documented in NEDC-31336 is applied to calculate allowable values and setpoints.
NUMAC-PRNM equipment performance specifications are described in NEDC-32410P-A. The NRC
. accepted NEDC-32410P for referencing in license applications in an SER transmitted by letter from B.
Boger (NRC) to D. Reigel dated September 5,1995.
Some setpoints do not have any analytical bases (i.e., the APRM Simulated Thermal Power (STP) - High Alarm and STP-High Trip setpoints and Rod Block Monitor (RBM) Downscale setpoints), but it is still necessqry to establish both a setpoint and an Allowable Value. For these cases, the methodology used was to establish a " design basis' limit (equivalent to the analytical limit) and then apply the same setpoint methodology to calculate allowable values and setpoints. Since there is no analytical limit for these setpoints, it is necessary to establish the design bases via some altemate method. That was done using engineering judgment with consideration of operating experience at plants with equivalent functions,.
relationships to setpoints with an analytical limit, and operational margins. The STP-High Alarm design basis value was selected based on plant experience and the goal of providing adequate waming to the operator when the normal plant operating region has been exited while preventing premature alarms due to riormal plant evolutions. The STP-High Trip setpoint was chosen to provide similar scram margin as the existing APRM system yet still be below the High Flux Scram setting which does have an analytical
. basis.. The RBM Downscale setpoint is discussed in the response to the next question below.
T8 Table 3.3.2.1-1 Chances:
Question f1)
RBM Downscale trip is not deleted in the topical report. PECO's basis for removing this trip is stated to be NUMAC OPRN's capability to eliminate the types of failures that are detected by this trip function.
Since NUMAC-OPRN specifically does not support deletion of this trip, provide the technical basis to justify the proposed change.
Response (1)
The pre-ARTS RBM operated such that each channel's flux average was gained up to equal the value of the reference APRM power at that point in time. Its trip setpoints were flow biased similar to the APRM's.~ Since the reference APRM value to which the RBM was " gain adjusted" to was variable over a wide range of power (theoretically 3% (downscale) to 100%), the RBM downscale setting was set to nominally 3%.
With the introduction of ARTS at PBAPS in 1994, the RBM flux average ' gain adjustment" or " null
- logic was changed to always gain adjust the RBM flux average to a value of 100% prior to rod withdrawal. All setpoints were calculated from an initial starting point of 100%. Since the RBM always " nulled' to 100%,
GE's originally proposed RBM downscale setpoint was nominally 90% which PBAPS initially implemented. The 90% downscale setpoint; however, caused excessive operator nuisance alarms
. during scram time testing and fast power reduction events where the local flux surrounding the control rod was reduced to below the setpoint during rod insertion. Following evaluation by both GE and PBAPS, the RBM downscale setpoint was reduced to a value consistent with the pre-ARTS setpoint.
This revised setting was applicable in identifying conditions within the RBM that prevented it from gaining
. the RBM average up to 100% by providing a downscale rod block.
The NUMAC RBM has self test capabilities built into the firmware of the device to detect abnormal operating conditions (such as failure to gain to 100%) and provide an inop alarm and associated rod j
block signal. No failure modes have been identified which would result in the RBM flux value being reduced to near zero without other alarms. This feature reduces the value of the RBM downscale
. setpoint to that of a potential " diagnostic aid" in troubleshooting certain inop conditions which have already been indicated by self-test. This reduced significance, coupled with the fact that no credit was given to the downscale function in any ARTS analyses by GE, lead PBAPS to conclude that the function is not necessary for inclusion into the Technical Specifications, i
l Our submittal dated March 1,1999 provided 'information on page 15 of Attachment 3 in response to NUMAC LTR paragraph 8.5.1.4. It includes additional discussion of the differences between the original l
analog processing hardware and the replacement digital processing equipment.
. Table 3.3.2.1 1 and associated Bases pages that reflect the Downscale Function are provided in if NRC staff determine that the Downscale Function is required.
I
Questiofl.f21 Topical Report has conditions (d) and (e) applicable to RBM-Inop trip function. PECO added conditions a, b, c and deleted condition e. This change is not discussed in the submittal. Also, the operability range of RBM under conditions a, b, and c are retained in the topical and changed by PECO to be "one-sided" to reduce the risk of non-compliance. This change will affect the RBM trip operability requirements as follows-(1) Low power range-upscale will have to be operable beyond 63.3% RTP (current operability range is 28.4% to 63.3% RTP).
(2) Intermediate power range-upscale will have to be operable beyond 83.3% RTP (current operability range is 63.3% to 83.3% RTP).
(3) High power range-upscale will have to be operable below and above 90% RTP (No upper and lower limit-current low limit is 83.3% RTP).
(4) Inop will have to be operable at or above 28.4% of RTP as per a, beyond 33.3% of RTP as per b, and below and above 90% RTP (no limit) as per item 3 above.
Explain how conditions a, b, and c, which are different, shall be simultaneously applicable to Inop in item 4.
Response (2)
The not effect of deleting condition (e) and adding conditions (a), (b) and (c) as applicable to the Inop Function is a more restrictive change to require the Inop Function to be operable when RTP is at least 28.4% as opposed to 64% in condition (e). To clarify the condition at which the Inop Function is required to be operable, conditions (b), (c) and (d) have been deleted and condition (a) retained. A similar situation occurs for the High Power Range-Upscale Function. As marked in the submittal, the High Power Range-Upscale Function is required to be operable above 83.3% and below 90% by condition (c),
and at or above 90% by condition (d), unchanged from the current requirement. However, to simplify the operability statement, the High Power Range-Upscale Function operability requirements have been clarified to require operability when RTP is at least 83.4% by deleting condition (d) and retaining condition (c) while deleting the criterion 'and < 90%" from condition (c).
The change in ' operability range" requirements for the Low Power Range-Upscale and Intermediate Power Range-Upscale appears to be a more restrictive requirement. However, because the Intermediate Power Range-Upscale setpoint is actually more restrictive than the Low Power Range-Upscale setpoint, and since the trip function is accomplished by common hardware, satisfying the
- perability requirement for the intermediate Power Range-Upscale Function also satisfies the operability o
requirement for the Low Power Range-Upscale Function. Similarly, satisfying the operability requirement for the High Power Range-Upscale Function also satisfies the operability requirement for the
' intermediate Power Range-Upscale Function and the Low Power Range-Upscale setpoint. The purpose of this change in the statement of the requirement is to eliminate the implication that the threshold point must be at exactly the value between each of the two ranges (63.3% and 83.3%) when the actual limits used as the basis for the setpoint analysis is one sided.
A revised Table 3.3.2.1-1 containing the clarifications is provided in Attachment 2.
1 ATTACHMENT 2