ML19249B778
| ML19249B778 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Surry, North Anna, 07200002, 07200055  |
| Issue date: | 08/29/2019 |
| From: | Dominion Energy Nuclear Connecticut, Virginia Electric & Power Co (VEPCO) |
| To: | Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| References | |
| 19-296 | |
| Download: ML19249B778 (2) | |
Text
ENCLOSURE 6 MPS2 COMPARISON MATRIX RCS POT. LOSS A.1 Serial No.: 19-296 Docket No.: 50-336 Dominion Energy Nuclear Connecticut, Inc. (DENC)
Millstone Power Station Unit 2
RCS RCS or SG Tube Leakage P-Loss 1 A. Operation of a standby charging (makeup) pump is required by EITHER of the following:
- 2. SG tube leakage.
OR B. RCS cooldown rate greater than (site-specific pressurized thermal shock criteria/limits defined by site-specific indications).
Serial No.: 19-296 Docket Nos.: 50-336 Page 1 of 1 Table 4 - MPS2 Comparison Matrix Category F: Fission Product Barrier Degradation RCS Pot. 1. UNISOLABLE RCS or The pump capacity of a standby MPS2 positive Loss SG tube leakage > 50 displacement charging pump, started on decreasing A.1 gpm excluding normal pressurizer level, is not indicative of a potential loss of reductions in RCS the RSC barrier. Control room indications are inventory (e.g.
available to provide the operator adequate capability letdown, RCP seal to maintain pressurizer level within specified limits and leakage) identify UNISOLABLE RCS or SG tube leakage> 50 gpm excluding normal reductions in RCS inventory (e.g., letdown, RCP seal leakage).
The design flow of the MPS2 positive displacement charging pumps is 44 gpm. Decreasing pressurizer level would be indicative of a> 50 gpm leak rate with two charging pumps running (88 gpm), a minimum design letdown flow of approximately 28 gpm and assumed RCP bleed off flow of up to 10 gpm. Therefore, continued decreasing level with two charging pumps running would not require operators to make a mass balance calculation. By contrast, two charging pumps running and system level stabilized would likely indicate leakage < 50 gpm and not constitute an inability to maintain pressurizer level within specified limits.
MPS2 has implemented the alternative threshold wording consistent with NEI 99-01, Rev. 6, RCS Potential Loss 1, Developers Notes.