ML15134A359

5/11/2015, Meeting Slide Regarding Pre-Submittal Meeting for Palo Verde Unit 1, 2, and 3 Updated Spent Fuel Pool Criticality Analysis

ML15134A359
Person / Time
Site:	Palo Verde
Issue date:	05/11/2015
From:	Arizona Public Service Co
To:	Lisa Regner Plant Licensing Branch IV
Regner L
References
Download: ML15134A359 (34)

Text

Pre-Submittal Meeting for Palo Verde Unit 1, 2, and 3 Updated Spent Fuel Pool Criticality Analysis May 11, 2015

Purpose

• Present and discuss planned licensing changes

- Update spent fuel pool (SFP) criticality analysis

- Add neutron absorbing inserts to SFP racks 2

Objectives

• Updated criticality analysis will

- Provide basis for replacing non-conservative Technical Specification (TS) caused by missed power uprate impact

- Include Next Generation Fuel (NGF)

• Account for reactivity effects of integral fuel burnable absorber (IFBA)

- Maintain full core offload capability 3

Borated Aluminum Inserts

• Additional reactivity hold down is planned to meet 10 CFR 50.6850 68 and maintain full core offload capability

- Th Thermall h hydraulic, d li seismic, i i structural, t t l and d

pool cooling calculations will be updated as needed

- Add a coupon surveillance program to monitor material performance 4

TS Changes

• TS 3.7.17 - Spent Fuel Assembly Storage

- Incorporate new burnup and enrichment curves

- Display information with the polynomial explicitly stated

- Include diagrams of approved arrays 5

TS Changes

• TS 3.7.15 - Fuel Storage Pool Boron

- Currently 2150 ppm

- May increase in response to accident conditions analysis 6

TS Changes

• TS 4.3 - Fuel Storage

- Incorporate new arrays

- Update boron concentration

- Reduce radially averaged enrichment from 4.8 wt% to 4.65 wt%

7

New TS

• 5.5.21 - Spent Fuel Storage Rack Neutron Absorber Monitoring program

- Will consider upcoming NRC Generic Letter Monitoring of Neutron-Absorbing Monitoring Neutron Absorbing Materials in Spent Fuel Pools

- Recent Dresden OE

- License extension

- Plant decommissioning 8

Implementation

• Prior to NGF implementation in each unit

• Considering installing inserts under 10 CFR 50.59 50 59

• C Considering id i a li license condition diti ffor a specified period of time to transition between TS 9

Methodology

• Based on

- ISG ISG-2010-01, 2010 01 Staff Guidance Regarding the Nuclear Criticality Safety Analysis for Spent Fuel Pools

- NEI 12-16, Guidance for Performing Criticality Analyses of Fuel Storage at Light-Water Reactor Power Plants Plants, Revision 1

- EPRI Depletion Benchmark Reports

- Multiple p NUREGs 10

Recent Licensing Actions

• Methodology similar to:

- Comanche Peak

- Prairie Island

- Turkey Point

• Insert material similar to:

- LaSalle

- Peach P h Bottom B tt

- Quad Cities

• Criticality code usage similar to:

- Millstone 2 11

ISG Item 1 - Fuel Assembly Selection

• Palo Verde will demonstrate that variations in design are adequately accounted for in a single, limiting, fuel assembly design

- CE St Standard d dF Fuell

- CE Value Added Pellet

- Westinghouse NGF (8 LUAs)

- AREVA Advanced CE CE-16 16 HTP (8 LTAs) 12

ISG Item 2 - Depletion Analysis

• Depletion parameters will impact the isotopic inventory of burned fuel

• Major depletion inputs

- Fuel type

- Axial burnup

- Moderator temperature

- Reactor power

- Soluble boron

- Burnable absorbers 13

ISG Item 2.a - Depletion Uncertainty

• The EPRI methodology will be used to demonstrate the 5% depletion uncertainty is conservative for Palo Verde

• Fission product uncertainty explicitly considered 14

ISG Item 2.b - Reactor Parameters

• Limiting axial moderator temperature profiles derived past, past present, present and anticipated profiles

- Same methodology gy employed p y at Comanche Peak

• Analysis performed at 4070 MWth

• Licensee controls include verification of radial power distribution di ib i anddT T-cold ld 15

ISG Item 2.c - Burnable Absorbers

• Palo Verde has used the following integral burnable absorbers

- B4C rods in CE STD Fuel

- Erbia in CE STD Fuel and Value Added Pellet

- Integral Fuel Burnable Absorber (IFBA) in NGF

- Gadolinia in AREVA Fuel

• Analysis will not credit Erbia, Erbia B4C, C or Gadolinia

• NGF fuel modeled with IFBA in all 236 pins for depletion p analysis y onlyy

- Pool model assumes no burnable absorbers 16

ISG Item 2.d - Rodded Operation

• Palo Verde does not operate with control rods inserted

- Guide tube wear program

• End of cycle check will ensure that fuel assemblies experienced an insignificant amount of rodded operation at hot full p

power 17

ISG Item 3 - Criticality Analysis

• SCALE 6.1.2 will be used in the analysis

- KENO V.a solves the eigenvalue (keff ) problem in 3D using the Monte Carlo method

- 238 Group ENDF/B-VII will be used as the library

- Millstone LAR used SCALE 6.0 with the KENO V.a module and 238 Group ENDF/B-VII library 18

ISG Item 3.a - Axial Burnup Profile

• Bounding axial burnup profiles selected from past, past present, present and anticipated profiles

-CCycle l specific ifi li licensee controls t l iinclude l d checks h k on cutback regions (blanket), fuel design, and moderator temperature

- Same methodology used at Comanche Peak and Prairie Island 19

ISG Item 3.b - Rack Model

• Dimensions and tolerance of racks are traceable to design documents

• Borated aluminum insert B-10 B 10 areal density conservatively modeled at quantity less than minimum certified areal density 20

ISG Item 3.c - Interfaces

• All interfaces are evaluated and all interfaces are an acceptable 2x2 array

- Palo Verde has only one rack design

- No gaps modeled between rack modules 21

ISG Item 3.d - Normal Conditions

• Analysis demonstrates that keff 0.95 at less than the TS required boron concentration for:

- Fuel movement

- Fuel inspection and reconstitution

- Foreign Object Search and Retrieval

- Limiting normal condition to initiate accident identified 22

ISG Item 3.e - Accident Conditions

• Analysis demonstrates that keff 0.95 at less than the TS required boron concentration for

- Misloaded or dropped single fresh fuel assembly into, outside of, or on top of spent fuel racks

- Multiple misloaded fuel assemblies

- Loss of SFP cooling

- Seismic events 23

ISG Item 3.e (contd.)

• Limiting dilution event reduces pool boron from 2150 ppm to 1900 ppm

• TRM requires boron concentration to be maintained at 4000 ppm 24

ISG Item 4 - Code Validation

• Will perform criticality code validation in accordance with NUREG/CR-6698

- Data carefully considered to identify trends consistent with NUREG-1475 NUREG 1475

- HTC experiments will be included

• Fission products will be explicitly accounted for

- No lumped fission products will be used 25

Palo Verde Arrays

• 6 arrays will be analyzed

• Palo Verde expects to submit between 3 and 6 of the following arrays for approval

• Fi Finall d designs i specify if llocation ti and d orientation of borated aluminum inserts 26

Palo Verde Arrays

• Infinite array of 2 fresh fuel assemblies (Fr) with two blocked locations and no inserts Fr Fr 27

Palo Verde Arrays

• Infinite array of 2 fresh fuel assemblies (Fr) with two trash cans (TC) and two inserts Fr TC TC Fr 28

Palo Verde Arrays

• Infinite array of 3 low reactivity fuel assemblies (Lo) and 1 high (Hi) reactivity fuel assembly with 2 inserts Lo Lo Hi Lo 29

Palo Verde Arrays

• Infinite array of 2 high reactivity fuel assemblies (Hi) and one low reactivity fuel assembly (Lo) with one blocked cell and one insert Hi Lo Hi 30

Palo Verde Arrays

• Infinite array of 4 low reactivity fuel assemblies (Lo) with one insert L

Lo L Lo Lo Lo 31

Palo Verde Arrays

• Infinite array of 4 depleted fuel assemblies (De) with no inserts De De De De 32

Margin Maintenance

• Palo Verde will monitor the margin identified in the analysis

• Cycle specific checks of key input parameters

• 0.005 k additional margin reserved by Palo Verde

- Burnup and enrichment curves will be for keff = 0.99 33

Conclusion

• Palo Verde is proposing an acceptable methodology gy for performing p g SFP criticality y

analysis

• Permanently l installed ll d b borated d aluminum l

inserts will be credited in the analysis

• Submit LAR by Nov 2015

• Request NRC approval in 18 - 24 months 34