05000456/FIN-2013002-04
From kanterella
Jump to navigation
Jump to search
Finding | |
|---|---|
| Title | Boric Acid Transfer Pump Electrical Power Supply Not Safety-Grade |
| Description | Branch Technical Position RSB 5-1, Design Requirements of the Residual Heat Removal System, includes the following relevant Functional Requirements (Reference: BTP 5-1, Revision 2, July 1981, Page 5.4.7-13): 1. The design shall be such that the reactor can be taken from normal operating conditions to cold shutdown using only safety-grade systems. These systems shall satisfy General Design Criteria 1 through 5. 2. The system(s) shall be capable of bringing the reactor to cold shutdown conditions, with only offsite or onsite power available, within a reasonable period of time following shutdown, assuming the most limiting single failure. Per BTP 5-1, the processes involved in cooldown are heat removal, depressurization, flow circulation, and reactivity control. The cold shutdown condition, as described in the Standard TSs for a pressurized water reactor, refers to a subcritical reactor with a reactor coolant temperature no greater than 200 degrees Fahrenheit. The licensees CLB discussed that since the Instrument Air system is not a safety-grade (i.e. safety-related) system, it was not considered available for the purpose of the analysis. One consequence of losing instrument air is a CVCS letdown isolation since numerous air-operated valves fail to their closed position. Since letdown is isolated, the available RCS volume available for boration is limited and accommodated by the usable volume within the PZR both prior to the cooldown and following the cooldown. To accomplish shutdown boration, the station utilizes the highly concentrated boric acid storage tanks (BASTs) [~7000 parts per million (ppm) boron] relative to the less concentrated refueling water storage tank [~2000 ppm boron]. The Braidwood design required the use of the boric acid transfer pumps to pump water from the BASTs to the suction of the CVCS CCPs as part of the required flow path. Therefore, the BAST boric acid transfer pumps are credited in the licensees CLB and supporting analysis for achieving the necessary RCS boric acid concentration to reach cold shutdown conditions. The BAST boric acid transfer pumps were discussed in the approved Safety Evaluation Report. The licensee stated that the BAST boric acid transfer pumps (and CCPs) are train-oriented and can be powered from the EDGs. The licensee also stated that the BAST boric acid transfer pumps are not powered from engineered safety feature (ESF) buses. The inspectors questioned the apparent conflict between the two statements and subsequently determined that both statements are, in fact, correct. The BAST boric acid transfer pumps can be powered by the EDGs through the safety-related 4 kilovolt (kV) vital bus via a cross-tie breaker to a nonsafety-related 4 kV bus, cross-tied to a nonsafety-related 4 kV to 480 Volt (V) transformer, cross-tied to a nonsafety-related 480V bus and associated conductors and breakers. Braidwood Station was licensed as a Class 2 plant with regard to BTP RSB 5-1, which allows for a deviation from full compliance if it can be demonstrated that correction for single failure by manual actions inside or outside of containment or return to hot standby until manual actions (or repairs) were found to be acceptable for the individual plant. Therefore, the inspectors identified that the licensee was taking credit for nonsafety-related equipment, which appeared to be an apparent conflict with the CLB BTP RSB 5-1 functional requirements. The inspectors reviewed numerous CLB documents and could not identify any discussion on the acceptability of crediting manual action or repairs as discussed in the preceding paragraph. At the end of the inspection period, a detailed review of the CLB was in progress. This URI will remain open pending the completion of this review and determination of whether the current plant design is in conformance with NRC regulations. |
| Site: | Braidwood  |
|---|---|
| Report | IR 05000456/2013002 Section 1R04 |
| Date counted | Mar 31, 2013 (2013Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.04 |
| Inspectors (proximate) | A Garmoe E Duncan J Benjamin J Corujo Sandin J Laughlin J Neurauter J Steffes M Perry N Feliz Adorno R Ng T Goa Garmoee Duncan J Benjamin M Holmberg M Perry R Jickling R Ng T Daun |
| INPO aspect | |
| ' | |
Finding - Braidwood - IR 05000456/2013002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Finding List (Braidwood) @ 2013Q1
Self-Identified List (Braidwood)
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||