ML14203A313
| ML14203A313 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 07/22/2014 |
| From: | Joel Wiebe Division of Operating Reactor Licensing |
| To: | Demetrius Murray Exelon Generation Co |
| References | |
| Download: ML14203A313 (3) | |
Text
1 NRR-PMDAPEm Resource From:
Wiebe, Joel Sent:
Tuesday, July 22, 2014 9:50 AM To:
'Dwi Murray' Cc:
Subject:
Request for Additional Information Regarding Braidwood/Byron LAR Regarding Auxiliary Feedwater Cross-tie In reviewing the Exelon Generation Companys (Exelons) submittal dated January 31, 2012, related to Auxiliary Feedwater Cross-tie, for the Braidwood Station (Braidwood), Units 1 and 2 and Byron Station (Byron),
Unit Nos. 1 and 2, the NRC staff has determined that the following information is needed in order to complete its review:
- 1. Exelon states in its January 31, 2012, submittal that, The AF Train A unit cross-tie can be initiated before more severe conditions develop in the RCS that necessitate a bleed and feed strategy, thereby reducing the potential for fuel damage. The NRC staff needs additional information to evaluate this statement.
Provide the basis for this statement such as timed procedure walkthroughs and simulator runs that show core thermocouple temperatures for feed and bleed compared to AF cross-tie use. Include a discussion of the time to:
Close the unit 2 isolation valves Close the unit 2 isolation valves (via air isolation) - field operations Clear red tags on 1AF036, 2AF036 - field operations Unlock 1AF036, 2AF036 - field operations Start Opposite units Auxiliary Feedwater pump Describe if time validations were performed on the Auxiliary Feedwater crossties in the simulators that support the proposed actions to implement the crosstie versus feed and bleed.
- 2. Attachment 3 of the January 31, 2012, submittal provided an example procedure that directs the operators to initiate the AF cross-tie. The NRC needs additional information to understand the use of the AF cross-tie in relation to feed and bleed.
Provide a discussion or additional procedures that clarify the use of the cross tie in relation to feed and bleed. For example, is feed and bleed initiated in parallel with the AF cross-tie, after, or before?
- 3. The January 31, 2012, submittal proposed UFSAR changes that authorize use of the AF cross-tie in the event of a beyond design basis accident in a unit. The changes recognize that the AF pump used to supply water through the cross-tie is inoperable for the non-accident unit and proposes to use the current technical specification (TS) limiting condition for operation (LCO) to limit operation of the non-accident unit. Exelon states that this is a temporary relaxation of the single failure criterion for the non-accident unit. The NRC staffs preliminary determination is that use of the TS LCO in this manner is not acceptable and cannot be approved. The use of the TS LCO is for those instances which are inadvertent (equipment failure) or are intended to improve the reliability or risk (corrective or preventive maintenance) to the unit the equipment is designed to support. The fact that a temporary relaxation of the single failure criteria is necessary indicates that the equipment is not designed to support the other unit.
Provide additional information or supplement the submittal to provide an acceptable resolution.
- 4. The January 31, 2012, submittal provided an evaluation that the AF systems can be shared between units and meets GDC 5 because an orderly shutdown and cooldown of the non-accident unit could be
2 accomplished using the main feedwater system. GDC 5 states, Structures, systems, and components important to safety shall not be shared between nuclear power units unless it is shown that their ability to perform their functions, including, in the event of an accident in one unit, an orderly shutdown and cooldown of the remaining units, is not significantly impaired by the sharing." Elsewhere in the submittal the licensee states that. The AF system is designed with suitable redundancy to offset the consequences of any single failure, with one exception during AF Train A unit cross-tie use. The NRC staffs preliminary determination is that the loss of single failure capability for the non-accident unit is inconsistent with the GDC 5 requirement that the sharing not result in significant impairment of function.
Provide additional information or supplement the submittal to provide an acceptable resolution.
Hearing Identifier:
NRR_PMDA Email Number:
1438 Mail Envelope Properties (2C5246E2C48F77418DF2EE22F3C7DE973158EFB412)
Subject:
Request for Additional Information Regarding Braidwood/Byron LAR Regarding Auxiliary Feedwater Cross-tie Sent Date:
7/22/2014 9:49:49 AM Received Date:
7/22/2014 9:49:00 AM From:
Wiebe, Joel Created By:
Joel.Wiebe@nrc.gov Recipients:
"'David Gullott'" <David.Gullott@ExelonCorp.com>
Tracking Status: None
"'Dwi Murray'" <Putri.Kusumawatimurray@exeloncorp.com>
Tracking Status: None Post Office:
HQCLSTR02.nrc.gov Files Size Date & Time MESSAGE 4126 7/22/2014 9:49:00 AM Options Priority:
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