ML20085N281
| ML20085N281 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 06/23/1995 |
| From: | Saccomando D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9506300131 | |
| Download: ML20085N281 (5) | |
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' Commonwealth IAimn Company 1400 Opus Place Dou.ncrs Grove. IL 60515 June 23, 1995 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn:
Document Control Desk
Subject:
Additional Information Regarding Supplement to Technical Specification Amendment Request for Section 3.4.9.3 Braidwood Unit 1 and 2 NRC Docket Numbers 50-456 and 50-457
Reference:
D. Saccomando letter to the Nuclear Regulatory Commission (NRC) dated June 8, 1995, transmitting Supplement to Technical Specification Section 3.4.9.3 The Reference letter transmitted Commonwealth Edison Company's (Comed's) supplement to the Technical Specification amendment request for Section 3.4.9.3.
In that letter, pages 22-25 were inadvertently not transmitted and therefore are included in this correspondence.
If you have any questions concerning this please contact this office.
I cerely,
,.,N
-,wN Denise M.
Sa mando Nuclear Licensing Administrator Attachment cc:
R. Assa, Braidwood Project Manager-NRR S. Dupont, Senior Resident Inspector-Braidwood J. Martin, Re Ional Administrator-RIII Office of Nuclear Safety-IDNS EDPOP.i 9506300131 950623 PDR ADOCK 05000456 P
PDR f
A rniconon>mpany
The recommended enable' temperature for the 16 EFPY Appendix G values for Braidwood Unit 1 is based *on the following relationship in'accordance with Branch Technical Position RSB 5-2 of Standard Review Plan 5.2.2:
RT, + 9 0 F + max ( AT,,ta )
Where:
RTmn is either the 1/4-t Adjusted Reference Temperature (ART)
(105.20F) or 3/4-t ART (83.9 F)
AT,,ta is the temperature difference between RCS water and either the 1/4-t (30.2930F) or 3/4-t (63. 042)F) metal temperature at the controlling location.
Performing these-calculations produces a bounding value of 220 F.
The actual enabling temperature for the LTOP system at Braidwood is then conservatively (LTOP enables sooner on plant cooldown) set 130 F higher at 350 F.
6.
What provisions in the TS would limit the start of an idle Reactor Coolant Pump (RCP) with a maximum temperature difference between the steam Generator (SG) and the RCS of no more than 50'F.
" Reactor Coolant System - Hot Shutdown,"
limits the start of an idle RCP when the maximum temperature difference between the SG and the RCS exceeds 500F.
This specification refers to a footnote which reads':
"A reactor coolant pump shall not'be started with one or more of the Reactor Coolant System cold leg temperatures less than or equal to 350 F unless the secondary water temperature of each steam generator is less than 50 F above each of the Reactor Coolant System cold leg temperatures."
TS 3.4.1.4.1,
" Reactor Coolant System - Cold Shutdown - Loops Filled," limits the start of an idle RCP when the maximum temperature difference between the SG and the RCS exceeds 500F.
This specification also refers to a footnote which reads identically to the footnote for TS 3.4.1.3.
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7.
Discuss the limitations in anergency Core Cooling system (ECCS) TS which could support the assumption used in the mass addition transient for LTOP design.
The Braidwood Unit 1 LTOP nominal PORV setp' int values were based o
on a mass addition event involving a single ~ centrifugal charging pump' operating with the charging line flow control valve fully open and the letdown line flow control valve in the Chemical and Volume Control System failed closed.
Also, LTOP analysis assumes a water solid RCS.
To ensure the LTOP analysis and mass' addition transient assumptions are met, Specification 3.5.3, "ECCS Subsystems - T,y
< 350 F," limits operable ECCS subsystems to one subsystem consisting of an operable centrifugal charging. pump, an operable Residual Heat Removal (RHR). System Heat Exchanger, an operable RHR pump and an operable water source for these pumps.
Further, TS 3.5.3 requires that:
" A maximum of one charging pump shall be OPERABLE and that pump shall be a centrifugal charging pump, whenever the_ temperature of one or more of the RCS cold legs is less than or equal to 330 F."
This requirement is contained in a footnote referenced in the body of the Specification.
Surveillance requirement 4.5.3.2 of Specification 3.5.3 states:
"All charging pumps and Safety Injection pumps, except the'above allowed OPERABLE pumps shall be demonstrated inoperable by verifying that the motor circuit breakers' are secured in the open position at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> whenever the temperature of one or more of the RCS cold legs is less than or equal to 330 F. "
Although Specification 3.5.3 leaves a RHR pump operable, the mass addition transient associated with one centrifugal charging pump remains the most limiting event due to the very low shut-off head (approximately 200 pounds per square inch gauge (psig)) of the RHR pumps as compared to the shut-off head of the centrifugal charging pumps (approximately 2600 psig).
In Modes 5 and 6 with Pressurizer (PZR) level greater than 5%,
Specification 3.5.4.1, "ECCS Subsystems -
T,,,, Less than or Equal to 200 F - Pressurizer Level Greater than 5%, " requires that all Safety Injection Pumps be inoperable.
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s In addition to Specifications 3.5.3 and 3.5.4.1,. Specifications 3.1.2.1, "Boration Systems Flow Path'- Shutdown" and-3.1.2.3, i
" Charging Pump - Shutdown," require that:
" A maximum of one charging pump shall be OPERABLE and that pump shall be a centrifugal charging pump, whenever the temperature of J
one or more of the RCS cold legs is less than or equal to-3300 F."
3 This requirement is contained in a footnote referenced in the j
body of the Specifications.
4 8.
Discuss the TS limitations that could assure no more than one RCP operating when the RCS temperature is less than 120'F.
There are no TS limitations on starting more than one RCP when the RCS temperature is less than 120 F.
This limitation is contained in Braidwo'od Operating. Procedure (BwOP)RC-1, "Startup of a Reactor Coolant Pump," Braidwood Unit 1 General Operating Procedure (1BwGP) 100-1, " Plant Heatup" and 1BwGP 100-5, " Plant Cooldown" These procedures contain Limitation and Action steps that. state i
in part; j
"No more than 2ng RCP shall be running when the RCS temperature is s120 F and the PZR is solid. "
This particular step is identified as a commitment step in these procedures and thus cannot be removed from the procedure unless the commitment it is based on is cancell'ed.
Since Braidwood Station requires verbatim procedure compliance, these procedural steps are considered adequate to ensure no more than one RCP is running when RCS temperature is less than or equal to 120 F.
9.
Confirm that the transient analysis performed in developing PORV setpoints assumes water solid conditions in RCS.
1 The transient analysis used for the determination of PORV setpoints for LTOP at Braidwood assumes that the pressurizer and the remainder of the RCS is in a water solid condition.
This is consistent with the design basis for LTOP as defined in WCAP 14040, " Methodology used to develop Cold Overpressure Mitigating System Setpoints and RCS Heatup and Cooldown Limit Curves."
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10.
Discuss the reasons for the highest PORV setpoint at the RCS l
temperature of 200'F.
l For the proposed Figure 3.4-4a associated with this submittal,-
the peak occurred at 2500F.
J The LTOPS setpoint limit curve is based on protecting the Reactor Vessel from non-ductile failure in the event of a postulated mass injection event or a postulated heat injection event.
At the low end of the LTOPS temperature range, the mass injection event is the most limiting.
At the high end of the LTOPS range, the heat' injection event becomes most limiting.
Also, at the high end of the range, the LTOPS limiting setpoint is based on not exceeding the constant 800 psig PORV discharge piping limit.
In the region where the heat injection event becomes significantly more limiting, the combination of the shift in limiting event, PORV pressure overshoots and the constant 800 psig PORV discharge piping limit result in a reduction in the allowable LTOPS maximum setpoint, hence a peak in the curve occurs.
11.
Provide a tabulation of the data obtained in your analysis for the limiting pressure in Appendir G, the limiting pressure allowed by ASME Code Case N-514, the PORV setpoint with instrument uncertainties, the incr===nt of pressure during the limiting transient, and the peak transient RCS pressure at 70'F, 15 0 *F, 2 0 0'F, 3 0 0'F, and 3 5 0'F.
See Table 2 in this attachment.
12.
Confirm that the PORV setpoints will prevent overpressurization of the RHR' System.
The PORV setpoints selected as part of the LTOP analysis do not specifically consider protection of the RHR system from overpressurization.
The issue of potential RHR system overpressurization during an LTOP event was addressed by Commonwealth Edison'in 1990 as a response to a notification by Westinghouse of RHR system concerns.
The three concerns identified by Westinghouse in this notification are discussed below.
1.
RCS LTOP events may exceed the capabilities of the RHR relief valves.
The most severe credible transient considered in the design of the Braidwood RHR relief valves is a mass input event in which one centrifugal charging pump is discharging into the RCS in an unthrottled condition while RCS letdown is isolated.
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