ML20137T859

Suppl 4 to Plant Transient Analysis for Hb Robinson Unit 2 at 2,300 Mwt W/Increased Fn Delta H:Inadvertent Loading & Operation of Fuel Assembly in Improper Position

ML20137T859
Person / Time
Site:	Robinson
Issue date:	11/01/1985
From:	Adams F, Holm J, Stone I SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER
To:
Shared Package
ML14192A714	List: ML20137T859
References
XN-NF-84-74, XN-NF-84-74-S04, XN-NF-84-74-S4, NUDOCS 8512090144
Download: ML20137T859 (13)

Text

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_3 I _ A. . ..: XN -NF 74 SUPPLEMENT 4 PLANT TRANSIENT ANALYSIS FOR H.B. ROBINSON UNIT 2 AT 2300 MWt WITH INCREASED F)H SUPPLEMENT 4 Inadvertent Loading arid Operation of a Fuel Assembly in an Improper Position NOVEMBER 1985 RICHLAND,WA 99352 EXXON NUC_ AR COV 3ANY NC.

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' XN-NF-84-74 -

Supplement 4 Issue Date 11/1/85 PLANT TRANSIENT ANALYSIS FOR H. 8. ROBINSON UNIT 2 at2,300MWtWITHINCREASEDFNH Supplement 4 Inadvertent Loading and Operation of a Fuel Assembly In An Improper Position

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Prepared by: . J - }'/t, % U I.Z. Stone,fngineer PWR Ne troni.s Prepared by: , , /A, i ' J C F4 T. Adams', . Le'ad Engineer PWR Safety Analysis Reviewed by: I bw

1. )5.'Holm, Manager I /fff PWR Safety Analysis Reviewed by: 2, r% .- /acw sc E B. Skogen/} Tanager PWR Neutronics" Reviewed by: M R. A'. Copeland rdfs-PWR Reload Licensin Approve: I f H.E.Williampn, Manager f it. / / fl u s'3 Licensing S'afety Engineering Approve: Y( i /Am:A :

T. W. P~atten, Manager /

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< G. L. Ritter, Manager l Fuel En ineering & Technical Services Concur:

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Customer Services Engineering

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CUSTOMER DISCLAIMER

' IMPORTANT NOTICE REGAADING CONTENTS ANO USE OF THl3 OOCUMENT PLEASE READ CAREPULLY Eamon Nussear Company's warrantime and representnoons consomme me ashpast mester of eie doesment are those set for1h in me .^,__.. :

heeussen Eamon Numiser Company, Inc. and the Cuesomer purement to which this desummet is issued. AesonHngly, esempt as oeermee emprouly provided in such Agreement, nesther Eamon Nealear Company, Inc. not any person asting on its behalf mehes muy warranty or representsoon, empressed or isnatied, wee respost to the assuresy, eenspieneness, or usefulness of the issforneseien eenemmed in this documest, or that the uns of any informenon, apparamas, metod or presses dienteesd in thes document wil not infrings prtwesely owned rights; or aumanes any liehetenes wee resseet to the use of any issformoeon, apparsass, meshed or prosess diestened in eis document.

The infermoeien cosnemed herein is for the soie use of Cussemer In order to esoid imperment of riglets of Emaon Numiser Company, Inc.

in poennes or inwonoons which may be instuded in the informenon contemed in eie desument, the resspeent, try its assentense of this doesment ayees not to pashiteh or rneke puidie use (in the poesnt use of the term) of such infermoeon unel se authorteed in wrmng by Eamon Nuc6 ear Company, Inc.

or unal after sia (4) months follounng . or espersoon of the sferessed Ayeoment and any entensson theseof, unies otherweso expreesty prended in the ? _ ._ No rights or liseness in or to any poesnte se imposed try the fumieheng of this doesment.

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1. 0 I NTR000CT I ON . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

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2.0 SUMARY..................................................... 2

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3. 0 GE NERAL DESCR IPT ION . . . . . . . . . . . . ... . ' . . . . . . . . . . . . . . . . . . . . . . . . . 3 L

g 4.0 ANALYTICAL' METHODOLOGY...................................... 4

(? 'S'.0 INADVERTENT FUEL' ASSEMBLY-L0ADING........................... 5

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~~6 . 0 l R E F E R E N CE S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 r

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.m .1 XN-NF-84-74 Supplement 4

. 1^.0 INTRODUCTION pThis report presents the results of the analysis of the Inadvertent Loading

-and'0peration of a Fuel Assembly in an Improper Position for-Cycle 10 in

H.B. Robinson Unit 2. These specific calculational results are being provided in addition to the administrative procedures previously outlined in Reference'1'.

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.'The ' analysis of the inadvertant loading of a fuel assembly has considered a'.s'pectrum of fuel assembly misloadings which also include the effects of

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'gadolinia depletion;and the misloading of a Part Length Shielding Assembly

'(PLSAs),t ' The analysis assumes that hot full power is equal to 2,300 MWt._

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2.0 . SLHMARY Fuel assembly loading errors are prevented by administrative procedures

. implemented during core . loading. These ' administrative procedures make it extremely unlikely that.an assembly . sill be misloaded.

For the unlikely ev5nt that a fuel loading error would occur, the analysis

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to determine the effect on power peaking considers two (2) categories of misloadings;' detectable and undetectable. To determine whether or not a

.particular misloading is detectable, the deviation from incore detector-readings for the correctely loaded core is calculated. Misloading events that result in deviations of 20% or more from the incore detector readings

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for the correctly loaded core are assumed to be detectable. Loading errors in the-. detectable category will be found prior to exceeding 30% of rated power. Analysis shows that the Cycle 10 power peaking associated with

' detectable misloadings can be tolerated at 30% of rated core power, without

. penetrating the ONB SAFDL'.

'For those cases - which are assumed to be undetectable, the maximum calculated value of FaH is 1.81 at full power. As was demonstrated in the

. analysis of the Static Misalignment of a Single Full Length RCCA (Event 15.4.3)(2), an FaH Of.l.94 can be tolerated during full power steady-state -

- operation without penetration of the DNBR SAFDL. The misloading event for-

Cycle.10 will not, by itself, result in penetration of the DNBR.SAFDL.

- Should an independent Condition II event occur with the core in a misloaded

' configuration, some fuel may experience boiling transition. The extent of

-fuel- failure' and -potential for radiological release would be conserva-tively bounded by the result reported in Reference 2 for the Single Control

- Rod -. Withdrawal. event, which considered an FaH of 2.096. Thus, the misloaded assembly event will not result in a violation of any radiological criteria.

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-3.0 . GENERAL DESCRIPTION

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.'. METHODOLOGY -

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1The neutronics analytical methods'used in this analysis,are discussed in

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5.0 INADVERTENT FUEL ASSEMBLY LOADING l

l 15.4.7 INADVERTENT LOADING AND OPERATION OF A FUEL ASSEMBLY IN AN TRFROPER POSITION 15.4.7.1 Identification of Causes and Event Description Core loading errors arise from the loading of one or more fuel assemblies into improper core locations. This can result in changes in the power distribution and increases in local power density which may go undetect-able by incore instrumentation.

Reactor protection for the misloaded fuel assembly event depends on administrative plant procedures. To reduce the probability of core loading errors, each fuel assembly is marked with an identification number nnd loaded in accordance with a fuel loading or shuffle procedure to achieve the design core loading plan, Reference 1. The location of each assembly is verified prior to replacing the upper internals.

Incore instrumentation is used to determine the core power distribution and can also be used to monitor for possible misloaded assemblies. The instrumentation includes 48 incore thimble tubes to accommodate incore neutron flux probes. Incore flux maps are taken at cycle startup and during initial power ascension at power levels of 30%, 70%, 90%, and 100%

of rated thermal power, and at monthly surveillance intervals thereaf ter.

In the unlikely event that a loading error occur.s, the power distribution will be changed by an amount proportional to the change in reactivity of the misloaded assembly. Large changes in the measured power distribution relative to the projected power distribution will be readily detectable by the incore instrumentation system at startup and during initial power ascension. However, small changes in the measured power distribution may

6 XN-NF-84-74 Supplement 4 go undetected by startup power ascension flux maps and continued operation at rated power can resuit in an increase in the radial peaking factor primarily for the case where the misloaded assemblies are the fresh gadolinia-bearing assemblies. If power operation persists with radial peaking f actors in excess of Technical Specification limits due to an undetected misloading event, the DNBR SAFDL may be penetrated.

15.4.7.2 Analysis Method A spectrum of misloading events has been analyred with the XTGPWR code for the Cycle 10 core loading plan in H. B. Robinson Unit 2. Initial calculations of the steady-state power distribution were all performed for beginning-of-life at 2,300 MWt (HFP) conditions using a full core 3-dimensional twenty-four (24) axial node model. Full core power distri-butions were calculated for the correctly loaded core and for a spectrum of misloading configurations. A misloading that resulted in a greater than or equal to 20% increase in the misloaded assembly power was considered to be detectable. The 30% power level map can be used as an early detection of a misloaded assembly since the power distribution changes only slightly during power escalation.

For undetectable misloading cases, the analysis focuses on core power peaking limits. If power peaking values for the misloaded core are calculated not to exceed Technical Specification limits (including un-certainties), no further evaluation is necessary as DNB will not be exceeded. If calculations indicate that Technical Specification peaking limits could be exceeded, additional analysis is necessary. The ad-ditional analysis includes a DNBR determination. 'If penetration of the XNB critical heat flux correlation safety limit has occurred, then a deter-mination of the fraction of the fuel to experience boiling. transition is made and the radiological consequences of such failures is assessed.

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7 XN-NF-84-74 Supplement 4 15.4.7.3!-Definition of Events Analyzed and Bounding Input i A spectrum of misloading. cases was analyzed. These cases represent the  !

- misloading of assemblies into core locations which are-designated to be

occupied by exposed or fresh fuel with different assembly reactivity char-acteristics.

- For those cases'which are found to be undetectable at begining-of-cycle, a

- cycle depletion calculation was performed to determine the power history '

'asla function of cycle exposure. From the results of the depletion calculation, the ' peak - Fan can be assessed relative to the Technical Specificatior. limit. Since plant procedures require that measured power

' distributions be -taken at monthly intervals, some of the undetectable events;at'BOL will be prevented from exceeding the Technical Specification ilimit by this periodic' assessment. For tnose misloading events that remain undetectable, a DNB ' analysis is performed to determine the potential

' impact on the core.

15.417.4' Analysis of Results The fuel misloading analysis determined the maximum value of Fag which can

be. expected to go undetected. The events analyzed can be categorized as the replacement of: -

_ 1), Exposed fuel with exposed fuel,

2) ' Exposed fuel with fresh fuel,

'3)- Fresh fuel with fresh gadolinia fuel; and ,

4) PLSAs with fuel.

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8 XN-NF-84-74 Supplement 4 Results of the calculations indicated that category (1) events are generally undetectable but never approached a power peaking configuration 1 in the core that would cause penetration of the DNBR SAFDL.

' The worst. undetectable misloading case occurred in category (2). Here, a l once-burnt assembly was interchanged with a fresh assembly containing 12 pins of gadolinia-bearing fuel pins. At the start of the cycle the Fay is 1.63 and with cycle depletion, the radial peaking factor Fag reaches a peak value of 1.81 at mid-cycle for the misloaded configuration.

The maximum FaH calculated to result from an undetected misloading error at

.fullf power is less than the 1.94 Fay considered in the MDNBR determination-for. the Static Misalignment of a Single Full Length RCCA reported in Reference 2. For that event, the calculated MDNBR is ' above the ~ XNB critical heat ~ flux correlation safety limit of 1.17., Therefore, the misloaded: assembly event (undetected case) is tolerable at full power

steady-state. operation without fuel failures.

_Should a limiting Condition II event occur with the core in a misloaded configuration, some fuel may experience boiling transition. In such an event, the numtrr of fuel failures and the potential radiological release are bounded by that reported in Reference 2 for the single control rod withdrawal event. That event considered an F4H of 2.096, well in excess of

'those calculated to - occur for the misloaded assembly event. The

. radiological consequences of a limiting Condition II event occurring with the' core in a misloaded configuration are acceptable.

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. REFERENCES' 1.' . - XN-NF.-83-72, Revision 2, Supplement 1, "H. B. Robinson Unit 2, Cycle 10 Safety Analysis Report, Revision 2 Disposition of Chapter 15 Events, Exxon Nuclear Company,~ July 1984.

'2. !XN-NF-84-74, Supplement 1, Plant Transient Analsyis. for H. ' B.

Robinson Unit -2 at'~2,300 MWt with Increased - Fgy, Supplement 1,

" Analysis of' Control Rod Misoperation Events (RCCA Misalignments)",

Exxon Nuclear Company, July 1984.

3. .

XN-NF-83-72, Revision 2,- H. B. Robinson Unit 2, Cycle 10 Safety

- Analysis Report, Exxon Nuclear Company, July 1984. '

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