ML13171A163
| ML13171A163 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/13/2013 |
| From: | Bailey J EnergySolutions, ZionSolutions |
| To: | John Hickman NRC/FSME/DWMEP/DURLD/RDB |
| References | |
| Download: ML13171A163 (2) | |
Text
From: Jack N. Bailey <jnbailey@energysolutions.com>
Sent: Thursday, June 13, 2013 12:29 PM To: Hickman, John Cc: Karl A. Axelson; Don Beckman; Patrick S. Thurman
Subject:
Response to Reviewer's Comments on the Heavy Loads Amendment Attachments: NRC Page Markup.pdf Follow Up Flag: Follow up Flag Status: Flagged John I have documented the responses to the questions discussed earlier this week between NRC and ZS personnel below.
Call with questions.
Jack
Background
The two question sets raised by the reviewer relate to Zion Stations (ZS) licensing basis for a Design Basis Earthquake (DBE). Zion DSAR section 3.7.1.1 identifies that The DBE is selected to be the largest potential ground motion based on site seismic and geological factors and uncertainties. The DSAR does not identify any other seismic events to be analyzed. The DBE is equivalent to the Safe Shutdown Earthquake (SSE) as previously described in the Zion UFSAR (which also included the Operating Basis Earthquake (OBE), which is now omitted from the DSAR). The ZS contractor has provided results for both the SSE (which is equivalent to our current, NRC accepted licensing basis DBE requirement) and the OBE (which is no longer applicable to Zion and is not a ZS licensing basis) in the request for Amendment for Heavy Loads, to be consistent with industry norms. However, performance of the OBE evaluation is not required to satisfy the ZS licensing basis.
Question from Reviewer On page 19 of 53 of your May 16, 2013, supplement (ZS-2013-0194) you state: The Zion DSAR requires allowable stresses for OBE to be in accordance with the AISC specification. A 1/3 allowable stress increase is permitted for earthquake forces per the specification. Can you please provide a specific reference to where this statement is in the DSAR.
Response
There is no specific statement in the DSAR that allows increasing the allowable stress by 1/3 per AISC for the OBE load case. The sentence in the Amendment Request was intended to refer to the AISC specification, not the DSAR as the source of the 1/3 increase. As stated above, the Zion DSAR no longer contains any reference to an Operating Basis Earthquake. The OBE calculations performed in our FHB evaluation, as stated above, were not necessarily required, but performed
by our contractor as part of its normal analysis approach and were not directed otherwise by ZS prior to the start of the project. Using the 1/3 increase in the allowable stress for the OBE load case would seem to be allowed by the ZION DSAR because there is no statement in the DSAR to the contrary and such a reduction is allowed by the AISC code. The DSAR refers to using AISC design criteria and this criteria is consistent with the original ZION UFSAR.
Question from Reviewer Based on the Table on Page 24 of 53 (attached):
- 1) the relationship in between shear wall column P7, P4, etc. to the SFP column 17 to 23 and P to W?
(Yellow Highlight),
Response
The contractors calculation ZION001-CALC-002 refers to particular shear wall sections as P2 through P11 and are provided in this table to aid ZS in validation against the referenced calculation. They are not directly related to column lines and can only be interpreted using the referenced calculation.
(2) missing Value (Green Highlight),
Response
For these two rows (Maximum In-Plane Shear Stress and Maximum In-Plane Moment), for all shear walls the SSE calculated value was less than the OBE allowable. Since this represents a bounding case, the individual SSE and OBE calculations were not required.
(3) below Table, foot note *SSE Max. Moment (IR = 1.111). This interaction ratio (IR) is unacceptable (need to see a conservative reanalysis [method] that has an IR below unity.
Response
The original bounding load case of SSE moment vs. OBE allowable had the IR of 1.111. When the contractor recalculated the SSE load case using the SSE allowable, the resulting IR for the SSE load case was 0.45. The contractor thus judged that the OBE calculation was not required based on the relationship between SSE and OBE loads. Since OBE calculations are not technically required for Zion, use of engineering judgment in this case is considered acceptable.