ML22024A056

Breakout Questions - Trps 142.1 and 149.13 - Fluence

ML22024A056
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Site:	Oconee
Issue date:	01/19/2022
From:	Angela Wu NRC/NRR/DNRL/NLRP
To:
Wu A, 301-415-2995
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Oconee (Units 1, 2, and 3) SLRA: Breakout Questions SLRA Section 4.2.1: Neutron Fluence Projections TRP 142.1: Neutron Fluence Question SLRA SLRA Background / Issue Discussion Question / Request Number Section Page (As applicable/needed) 1 4.2.1 4-22 *

Background:

Section 2.3 of ANP-3898P Please, explain why there is discusses the dpa adjustment methodology confidence in the dpa at the for the extended beltline that is mentioned location of interest in the in the SLRA. extended beltline and not in the fluence. In other words,

Purpose:

To better understand the dpa why is a multiplier needed for adjustment methodology employed for the dpa and not fluence, if dpa is extended beltline. typically calculated with fluence as an input. That is to say that elementary displacement theory states that the dpa is typically a product of the fluence, the scattering cross section, and the number of displacements produced per primary knock-on atom (PKA).

2 4.2.1 4-22 *

Background:

The dpa adjustment method Please explain the basis of described in Section 2.3 of ANP-3898P is this relationship and whether stating that the following relationship is differences in the neutron applicable spectrum from the beltline to

(. ) ( ) the extended beltline would

= affect the validity.

(. ) ( )

Purpose:

To better understand the dpa adjustment methodology employed for the extended beltline.

3 4.2.1 4-23 *

Background:

On page 4-23 of the SLRA it is Please explain how the stated that in the equivalent margins fluence of 1.5E18 n/cm2 was

analysis of the Linde 80 reactor pressure calculated for the RPV vessel nozzle welds reported in BAW-2192, nozzles welds in BAW-2192, Revision 0, Supplement 1P-A, Revision 0 Revision 0 Supplement 1P-A,

[Reference 4.2-13] and BAW-2178, Revision 0 and BAW-2178, Revision 0, Supplement 1P-A, Revision 0 Revision 0, Supplement 1P-A,

[Reference 4.2-14]) utilized an inside wetted Revision 0 and why that surface fluence of 1.5E+18 n/cm2. This is method was not employed for significantly higher than the 72 EFPY inside the SLRA.

wetted surface fluence values for the reactor pressure vessel nozzle welds reported in Table 4.2.1-1, Table 4.2.1-2, and Table 4.2.1-3 (highest at 3.50E+17 n/cm2).

Purpose:

To understand why there are differences in fluence calculations and methodologies used in the SLRA and BAW-2192, Revision 0 Supplement 1P-A, Revision 0 and BAW-2178, Revision 0, Supplement 1P-A, Revision 0.

SLRA Section 4.7.1.3: Reactor Vessel Internals Irradiation Embrittlement TRP 149.13: Reactor Vessel Internals Irradiation Embrittlement Question SLRA SLRA Background / Issue Discussion Question / Request Number Section Page (As applicable/needed) 1 4.7.1.3 B-64 *

Background:

Section B2.1.7 of the SLRA Please clarify and explain and states that As discussed in MRP-189, whether the fluence values B2.1.7 Revision 3, Sections 3.2, Item C and 3.3, from MRP-189 Rev. 3 that are Item B, neutron exposures are best- used in the Reactor Vessel estimate values in units of displacements Internals TLAA are best-per atom at the end of 80 calendar years estimate or conservative.

of operation, which are projected from existing 60-year documentation. In most instances, displacements per atom values

reported in MRP-189, Revision 3, are obtained from a conservative extrapolation of discrete ordinate transport 60-year best estimate analyses to 80-years to bound the B&W fleet. The 60-year discrete ordinate transport displacements per atom values were obtained using methods that comply with Regulatory Guide 1.190 for the reactor vessel as reported in BAW-2241NP-A, Revision 2.

Purpose:

To better understand the fluence values used for the reactor vessel internals TLAA.

2 4.7.1.3 4-119 *

Background:

Section 4.7.1.3 of the SLRA Please explain why there is states that The projected 72 EFPY such a large difference fluence values developed for the update between the fluence values of BAW-10008, Part 1, Revision 1 used to support the Reactor (Section 4.7-1) are TLAA and are Vessel Internals TLAA and the obtained from Reference 4.7-20. These ONS-specific MCNP/DORT-fluence inputs were developed based on calculated fluence values if the extrapolation of 60-year reactor vessel TLAA also used a BAW-internals transport calculations that were 2241P-A methodology.

developed using the RG 1.190 compliant methodology (i.e., deterministic discrete ordinates transport 3-D synthesis methods) developed for the reactor vessel as described in BAW- 2241PA, Revision 2, and are consistent with the fluence estimates reported in MRP-189, Revision 3 [Reference 4.7-19]. Since the BAW-2241PA, Revision 2 methodology is mainly concerned with reactor vessel fluence, some specific modeling

enhancements were required in order to accurately represent the reactor vessel internals components.

Additionally, Section 5.6 of ANP-3899NP states that The fluence/dpa used for the Oconee gap analysis (GALL SLR XI.M16A), which is based on MRP-189 Revision 3 and was developed to bound the B&W fleet of reactors, is reported in Table 5-2.

Furthermore, Table 5-3 of ANP-3899P compares the fluence values used to support TLAA and the ONS-specific MCNP and DORT-calculated fluence values.

Purpose:

To better understand the fluence values used as input to the TLAA and the ONS-specific MCNP/DORT-calculated fluence values.