ML20078C226
| ML20078C226 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 10/21/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078C225 | List: |
| References | |
| NUDOCS 9410310012 | |
| Download: ML20078C226 (5) | |
Text
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NUCLEAR REGULATORY COMMISSION j
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WASHINGTON, D.C. 20555-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 65 TO FACILITY OPERATING LICENSE NO. NPF-37, AMENDMENT N0.
65 TO FACILITY OPERATING LICENSE NO. NPF-66, AMENDMENT NO.
56 TO FACILITY OPERATING LICENSE N0 NPF-72, AND AMENDMENT NO. 55 TO FACILITY OPERATING LICENSE NO. NPF-77 COMMONWEALTH EDIS0N COMPANY BYRON STATION. UNIT NOS. 1 AND 2 BRAIDWOOD STATION. UNIT NOS. 1 AND 2 DOCKET N05. STN 50-454. STN 50-455. STN 50-456 AND STN 50-457
1.0 INTRODUCTION
Commonwealth Edison Company (Comed, the licensee), in a letter of March 23, 1994, as supplemented on July 26, 1994, proposed changes to the technical specifications (TS) for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2.
These changes involve TS requirements for a positive moderator temperature coefficient (PMTC) of up to +7 pcm per 'C; and a reduction in the minimum core flow.
As a consequence of these changes, TS changes are also proposed for the safety limit curves, safety system settings, boron concentration in various systems, and the Bases related to these TS, and to pH and departure from nucleate boiling (DNB).
The proposed changes were to apply to the units as they enter their respective refueling outages beginning with Byron, Unit 1, which is scheduled to restart from its current refueling outage in November 1994.
int March 23, 1994, submittal included two reports:
Commonwealth Edison Company Byron and Braidwood Units 1 and 2 Increased SGTP/ Reduced TOF/PMTC Analysis Program Engineering / Licensing Report (WCAP 13964, Revision 1); and Operating Parameter Uncertainties for the Byron /Braidwood Revised Thermal Design Procedure, Revision 0.
The staff requested additional information on July 26, 1994, regarding the proposed changes to the MTC and received a response from the licensee dated August 16, 1994.
The issues regarding approval of a PMTC are still under review by the staff.
Consequently, this Safety Evaluation will address only the o
" requests included in the March 23, 1994, submittal.
9410310012 941021 PDR ADOCK 05000454 P
e J 2.0 EVALUATION The Westinghouse Electric Corporation's (M) SGTP/TDF/PMTC report provided M analyses and evaluations for Byron and Braidwood on:
(1) the power capability parameters, (2) nuclear steam supply systems (NSSS), (3) NSSS design transients, (4) NSSS components, and (5) the relevant updated Final Safety Analysis Report (UFSAR) Chapter 15 events. Standard approval M procedures and methods applicable to the UFSAR were used. Complementary to that analysis is the uncertainty analysis that was also submitted.
It followed the M Revised Thermal Design Procedure, that is standard M methodology and had been used in previous licensee analyses approved by the staff.
I I
As indicated above, the proposed PMTC TS are still under review. However, ar.alyses for future plant operations presented in the submittal include the possible use of the maximum proposed PMTC. This includes all transients and accidents and the determination of requirements for various boron i
concentrations in the accumulators and in the refueling water storage tank to accommodate reactivity changes associated with the requested PMTC.
The boron requirements were increased in order to provide adequate shutdown margin throughout the cycle.
The need for change would arise from potential increased cycle energy design with the PMTC. The requirements for shutdown margin and the necessary increased boron was included in the safety analyses j
performed by M.
Thus, TS boron concentration values are generally increased l
from 2000 to up to 2300 ppm and the boration capability of systems increased.
There are also changes to the TS Bases on pH values for relevant systems.
Specific values and TS changes are discussed later.
Calculations were done to verify post-LOCA conditions, involving pH and dose levels with maximum boron i
levels.
The calculations and results for these shutdown margin and boron increase analyses follow normal procedures and are acceptable.
l The current flow rate requirement included in the TS for Byron and Braidwood l
(390,400 gpm) is based on a minimum measured loop flow of 97,600 gpm. This is used in the thermal design procedure presented in the UFSARs.
The licensee has proposed to lower the TS flow requirement to 371,400 gpm to provide a greater margin to actual flow, in anticipation of future steam generator tube plugging (SGTP). Associated with this change are proposed changes to TS for safety limits, safety system settings, flow rate requirements and the safety limit bases providing valves for departure from nucleate boiling ratio (DNBR) limits.
The M analysis program demonstrated that the steam generator tubes could be plugged to a maximum of 15 percent in any generator or to a reduction level of loop flow rate to the thermal design flow (TDF) limit of 89,700 gpm.
The H analyses included related phenomena such as loop flow asymmetry of 5 percent, along with the proposed PMTC and boron increases. The analyses were based on previously approved T(hot) reduction programs for Byron and Braidwood.
The core thermal limits were revised to include the use of the proposed flow changes and the use of the revised thermal design procedure. All systems affected by the change in core flow, plugging and associated parameters were reviewed and assessed by M for operation at the revised conditions.
The
e
. protection system setpoints were evaluated with the new reactor parameters and changed appropriately, and the transient and accident evaluations included these changes.
Standard, approved )! methods were used for these analyses, reviews and assessments. The results are acceptable.
Technical Specifications The following TS and Bases changes were proposed for Byron and Braidwood. All changes followed from or were justified by the analyses presented in the submittal.
Changes (2), (3) and (4), below, affecting the safety limit lines, the DNBR safety limit and trip system setpoint parameters, have occurred primarily because of the results of the uncertainty analysis of the Revised Thermal Design Procedure and the change in the core flow limit. The decreased flow limit (7) was proposed to provide more margin to the limit from actual flow rates to provide for future steam generator tube plugging.
The proposed baron pH changes of (6), (8), (9), (10) and (11), which were included in the safety analyses, were made to accommodate increased cycle energy possible with cycle designs with the proposed PMTC. Without approval of the PMTC (5) at this time, the increased boron changes are conservative.
With the exception of the PMTC change, the staff review determined that all proposed changes are acceptable.
In the July 26, 1994, supplement to the original submittal, the licensee proposed additional footnotes to several of the changed TSs to address implementation of the changes on a unit and cycle specific basis.
The original and supplemental footnotes, and indicated implementations are acceptable.
The changes to TS and Bases for both Byron and Braidwood from the original submittal are as follows:
1.
Table of contents; Figure 3.1-0 added.
2.
Figure 2.1-1, Reactor Core Safety Limits - Four Loops; limit lines changed.
3.
Bases 2.1.1, Reactor Core; changed to provide new DNBR safety limits for i
0FA and VANTAGE 5 fuel.
i 4.
Table 2.2-1, Reactor Trip System Instrumentation; flow limit and over temperature and over pressure delta T setpoints changed. Unit and cycle 1
implementation r, ": J.
5.
TS 3.1.2.5 and 6, Borated Water Source-Shutdown and Operating; boron concentration changed to between 2,300 and 2,500 ppm, and implementation
{
footnotes added, l
6.
TS 3.2.3, RCS Flow Rate; RCS total flowrate changed to 371,400 gpm.
7.
TS 3.5.1, Accumulators; boron concentration changed to between 2200 and 2400 ppm and implementation footnote added.
e i 8.
TS 3.5.5, Refueling Water Storage Tank; boron concentration changed to between 2300 and 2500 ppm and implementation footnotes added.
9.
TS 3.9.1, Refueling Operations / Boron Concentration; boron concentration changed to 2300 ppm.
10.
' Bases for the TS with flow or boron changes are changed to reflect the new values.
Bases 3/4.6.22, Spray Additive System, has the lower pH limit changed from 8.5 to 8.0.
3.0 CONCLUSION
S The staff has reviewed the information submitted by the licensee for Byron and Braidwood to justify proposed TS changes which provide for changes to the requirements or limits for the core flow as affected by steam generation tube plugging, and for associated changes to boron concentrations and pH level, safety system setpoints and DNBR safety limit values.
Based on this review, the staff concludes that appropriate information was submitted and the proposed changes to the TS are acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluent that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The i
Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public i
comment on such finding (59 FR 41802). Accordingly, the amendments meet the l
eligibility criteria for categorical exclusion set forth in 10 CFR l
51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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- s 6.0 00f4CLUSION The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
H. Richings Date: October 21, 1994
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