IR 05000327/1988060

Insp Repts 50-327/88-60 & 50-328/88-60 on 881222-23 & 890222.Major Areas Inspected:Review Licensee Resolution of Differences Between Measured & Predicted Critical Boron Concentrations Observed During Restart Testing

ML20246P703
Person / Time
Site:	Sequoyah
Issue date:	03/01/1989
From:	Long A, Linda Watson NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20246P690	List: IR 05000327/1988060 ML20246P685 ML20246P699
References
50-327-88-60, NUDOCS 8903280294
Download: ML20246P703 (10)

Text

-

" "

.

UNITED STATES

[pn Arag%,#

8\, '

NUCLEAR REGULATORY COMMISSION q REGION 11  !

k* % ,,

"t 101 MARIETTA STREET.N.W,.

ATLANTA, G EORGI A 30323

\ . . .> . /

.

q

Report Nos.* 50-327/88-60, 50-328/88-60 Licensee:' Tennessee. Valley Authority 6N 38A Lookout Place 1101 Market Square Chattanooga,.TN 37402-2801-Docket Nos.: 50-3'27 and 50-328 License Nos.: DPR-77 and DPR-79 Facility Name: Sequoyah Units 1 and 2

'

Inspection Conducted: December 22' and 23,1988,' anci February 22, 1989-

-

Inspectors: O R Lcw I//[hP >

'

A. R. Long, Pro'fect Engineer Date' Signed i !

's

.

-

1,. -q . . ,

Approved by: O/)

L. Vatd/on, Chief, Project Section 1

/

Dafe 6igned'

'

e

.

'

TVA Projects Division .- .

,

-

X ,

, .

-

, , .

['

?

'

Summary - +

.t .

Scope: This special, unannounced inspection was conducted to revie'w licensee resolution of the differences between measured and predicted critical'

boron concentrations observed during restart testing" of ~both . units,-

and to review methods being used to predict critical condition Results: One violation was identified during . the . inspection, with three - '

examples. The licensee failed to promptly initiate .the established corrective action process 1) when the licensee identified'in approx-

'imately May 1988 that the percentage of the- boron-10 isotope. in the reactor coolant system boron differed from receipt specifications, 2) when the licensee identified in November 1988 that the percentage:

of boron-10 differed from the value assumed in'the nuclear design:and'

safety analysis, and 3) when the licensee identified in December 1988 '

that a quality control inspector' had violated procedures- in April 1988 (VIO 327,328/88-60-01 - paragraph 2)..

Licensee actions to ' resolve the critical boron concentration discrepancies were otherwise acceptabl I i

Q32$?$$kb o

e

i

_ - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_ _

.

.

.

Two unresolved items" were identified during the inspectio The licensee identified that a quality control inspector had violated procedures by accepting bcric acid which did not conform to receipt specifications (URI 327,328/88-60-02 - paragraph 2). The licensee also identified that boric acid appeared to have been released from power stores prior to quality control inspection (URI 327,328/88-60-03- paragraph 2). These items remained unresolved pending additional NRC revie One licensee-identified violation was identified involving minor deficiencies in completed procedures. Adequate and timely corrective action was taken by the licensee and, per the provisions of the NRC enforcement policy, the violation was not cited (LIV 327,328/88-60-04 paragraph 2).

Licensee methods for predicting critical conditions were considered acceptabl The licensee centinued to demonstrate an ability to perform acceptably in the reactor engineering are Marked improvement in the control of nuclear engineering computer codes was observed relative to previous NRC inspection * Unresolved items are matters about which more information is required to determine whether they are acceptable or may involve violations or deviation _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _-

.

.

REPORT DETAILS Licensee Employees Contacted

• D, Adams, Supervisor, Chemical Technical Support

• ~Byrd, Manager, Projects Control and Financial Services

1. • M. Cooper, Manager, Compliance Licensing

• Fortenberry, Superintendent, Technical Support G. Gault, Supervisor, Reactor Engineering

• Johnson, Reactor Engineer T. Keys, Superviscr, PWR Core Design

'

T. Moffett, Systems Analyst, Nuclear Methods Development

• T. Pannell, Nuclear Quality Assurance J. Patrick, Superintendent, Operations

• Riden, Engineering Assurance Engineer

• R. Rogers, Superintendent, Plant Support

• S. Spencer, Nuclear Engineer, Licensing S. Stevens, Nuclear Chemist

• Attended exit interview on December 23, 1988

1. Participated in telephone call on February 22, 1989 NOTE: Acronyms used in this report are listed in the last paragrap . Followup on Previous Inspector Followup Items (92701,61707,72700)

(OPEN) IFI 327,328/88-53-02: Resolution of Issues Identified during Unit 1 Restart Test Program Inspector Followup Item 327,328/88-53-02 was initiated, in part, to track licensee resolution of the failure to meet the 50 ppm acceptance criterion on the agreement between measured and predicted HZP critical boron concentration during Unit I restart testing in November 1988. The measured HZP BOC critical boron concentration for Unit 1 was less than the predicted value by approximately 61 ppm. For the May 13, 1988, Unit 2 startup, the measured critical boron concentration was less than the prediction by 49 ppm, approaching the acceptance criterion but not exceeding i Although the critical boron measurements for both units were well within the 1000 pcm Technical Specification limit on overall core reactivity balance, measured and predicted critical boron concentrations typically agree within 20 to 30 pp NRC Inspection Report 327,328/88-53 documented the inspector's review of open CAQR CHS880067, which documented initial licensee actions to investigate the cause and impact of the Unit I critical boron concentra-tion discrepancy. The safety evaluation concluded that operation of the core with an actual excess reactivity the equivalent of 61 ppm less than the design value had no adverse effect on safet During Inspection 327,328/88-53, licensee engineers informed the inspector that a difference between the actual boron-10 isotopic concentration in

___ - _ _ - _ _ _ - _ _ _ _ _

. . . . .

.

.

'

. 2 the RCS boron and the value assumed in the nuclear design. and safety analysis contributed to the differences between the measured and predicted HZP critical boron concentrations for both unit During this inspection, the inspector reviewed licensee actions in response to the B-10 concentration issue, and reviewed licensee methodologies for predicting critical condition Boron-10 Isotopic Concentration The percentage of B-10 in natural boron varies. The General Electric Chart of the Nuclides,13th. edition,1984, documents a natural B-10 variation of 19.1 to 20.3 atom. percen The Sequoyah Nuclear -

Parameters and Operations Package (NUPOP) documented that a B-10 isotopic concentration of 19.8 atom percent was assumed by Westinghouse in the nuclear design and safety analysi Procedure SQA 159, " Standards and Guides for - Quality Assurance Level III Items", Appendix C, specified as a purchasing . requirement' for boric'

acid that the undepleted B-10 isotopic concentration be 1 .3 atom percent. However, the report of the independent. chemical and -

isotopic analysis-of the boron provided under contract 88NDA-47787A, dated March 1,1988, showed the actual B-10 concentrations to range from 20.05 to 20.08 atom percent. At the time of the NRC inspection, the licensee had not performed either a measurement or a detailed accounting to determine the actual isotopic composition of the. boron in the RCS. Licensee personnel stated to the inspector that the-percentage of B-10 in the RCS boron was' presumed .to be 20.06 atom percen .

The established licensee corrective action process was described in'

AI-12, " Adverse Conditions and Corrective Actions". This procedure required that a CAQR be initiated promptly upon the. identification of a condition adverse to qualit As of the beginning of this inspection, the B-10 concentration had not been addressed in a CAQ Therefore, no formal evaluation of possible safety impacts or unreviewed safety question determination had been performed, even though the boric acid was being used'in bot'. unit .

In each of the specific instances described below, licensee personnel identified conditions adverse to quality but failed to promptly-initiate the corrective action process required by AI-1 ) According to Chemical Technical Support. personnel, prior to the Unit 2 startup on May 13, 1988, personnel in the Waste Water Processing group. informed . CTS that the boric . acid B-10 concentration was not within the specifications of SQA 159, and questioned whether the boric acid was acceptable for use. .The-chemistry personnel concluded that the boric acid was acceptable chemically, but did not consider . the impact on neutron absorption and core rea::tivit The chemists considered changing the receipt specifications in SQA 159 _to match the as-received concentration, but this was not pursue _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ - _ _ _ . . _ _ _ _ _ . - -- _ _ _ _ _ - - - _ _ - _ - _ _ - _ _-

-

.

2) As previously discussed, prior to the conclusion of NRC Inspection 327,328/88-53 on November 12, 1988, licensee '

engineers informed the inspector that the B-10 concentration in boron being used in Unit I differed from the design value, and that this discrepancy indicated a problem with the quality control of material receip )

3) On December 6.,1988, documentation of improper QC acceptance of boric acid was found by the licensee. Although the composition analysis for the boron received under contract 88NDA-47787A clearly showed the contrary, the (AI 11) material and receiving report had been erroneously signed by a QC inspector on April 7, ,

'

1988, certifying that the B-10 concentrations were within the specifications of SQA 15 The failures to initiate the established corrective action process when it was identified that B-10 concentrations were not within specifications were identified as examples 1 and 2 of Violation 327,328/88-53-0 The QC acceptance in April 1988 of boric acid which did not conform to receipt specifications appeared to be a failure to adhere to the procedures applicable to the inspection and acceptance of quality controlled materials. This violation of procedures was identified by the licensee, and will be tracked as Unresolved Item 327,328/88-60-02 pending additional NRC review of the issue and the relevant procedural requirements. The failure to promptly implement the corrective action process established by AI 12 when the procedure violation was identified is example 3 of Violation 327,328/88-53-0 Although a CAQR on the B-10 concentration had not been initiated prior to the NRC inspection, the issue was being informally pursue The inspector noted that AI 12 required a CAQR to be promptly initiated when a condition adverse to quality is identified, but the procedure did not specify a time limit for CAQR initiatio The procedure did specify time limits for each step in the investigation, review, and approval process once a CAQR has been initiated. The inspector discussed with licensee management whether the lack of a time limit for initiating CAQRs represented a potential weakness in the corrective action program, in that CAQR initiation could be delayed in order to gain extra time for investigating a problem prior to bringing the AI 12 time limits into effect. The position of the licensee was that the three examples of Violation 327,328/88-60-01  !

were isolated cases of failing to implement AI 12 as intended, and did not indicate a weakness in the CAQR procedure or progra Licensee management agreed to address the basis for this position in additional detail in the response to the violatio Licensee personnel stated that the boric acid of contract 88NDA-47787A was possibly released from power stores prior to QC inspection, indicating a possible violation of material control procedure This issue was identified as Unresolved Item 327,328/88-60-03 pending confirmation and review.

- - _ _ _ _ _ _ _ - _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _

_ . _ _ _ _ _ _ _ _ _

.

.

b. Adequacy of Methods for Calculating Critical Conditions Effects of the difference between the presumed actual B-10 concen-tration and the value assumed in the nuclear design analysis would account for approximately 25 ppm of the observed critical boron concentration discrepancy on Unit 1, bringing the measured value well within the acceptance criterio The presumed B-10 concentration difference would account for about 10 ppm of the observed discrepancy during the Unit 2 restar Subsequent to the Unit 2 startup, Westinghouse had provided a refined HZP BOC critical boron calcula-tion, using a 3-dimensional model to account for the reactivity effects of axial burnup 51 story, which agreed with the measurement to within 5 pp Therefore, with the probable effects of the B-10 concentration taken into account, no significant core modeling errors were apparent in the HZP predictions for either uni Similarly, no significant modeling errors were apparent in the HFP critical boron concentration data for Unit 2 operation (attached).

The inspector discussed with the licensee how the measured and predicted curves were derived, and what factors were include The agreement between the measured'and predicted data was acceptable, and the observed effects of the extended shutdown on the agreement between measured and predicted boron concentrations were consistent with industry experienc Technical Specification 4.1.1.2 required a comparison of the overall core reactivity balance to predicted values at least once per 31 EFPD to demonstrate agreement within 1 percent delta k/k. The inspector reviewed the core reactivity balance calculations for the current cycle of Unit 2, performed per SI 120, "Overall Reactivity Balance."

The surveillance were adequately performed at the required intervals, with acceptable results, and no problems were identified with the methodology. The inspector confirmed that the licensee was including a correction for the reactivity effects of the extended shutdown in the SI 120 calculation The inspector reviewed the Unit 2 ECP calculations performed sub-sequent to the Unit 2 restart on May 13, 1988. All were calculated relative to the May 13, critical conditions. The reactivity differences between the measured and predicted critical conditions were approximated by the inspector in units of ppm of boron, using data from the NUPOP, and the results are tabulated belo Insufficient data was available to compile a similar comparison for Unit UNIT 2 REACTIVITY STARTUP MEASURED PREDICTED DIFFERENCE DATE CBC BANK D CBC BANK D PCM PPM 5/20/88 773 101 773 159 229 27 5/24/88 733 95 733 139 55 6

-

- .

.

UNIT 2 REACTIVITY STARTUP MEASURED PREDICTE DIFFERENCE DATE CBC BANK D CBC BANK D PCM PPM 6/7/88 696 119 697 167 16 I 6/8/88 827 145 827 118 99 11 i l

6/19/88 928 179 928 175 31- 4 The calculations which were reviewed encompassed a range of xenon conditions, and the inspector considered the data sufficiently representative to demonstrate the acceptability of the ECP methodology with respect to supporting the upcoming Unit l'startu To account for reasonable modeling uncertainties, TS 4.1.1.2. requires that predicted core reactivity values shall be normalized to correspond to the actual core conditions prior to exceeding a_ fuel burnup of 60_EFPD after each fuel loading. Similarly, by basing ECB/ECP calculations on previous actual critical conditions, the effects of modeling uncertainties and the B-10 difference are implicitly accounted for in the calculation During the inspection of the Unit 2 ECP calculations, a licensee reactor engineer identified a number of minor deficiencies in the -

completed procedure These included - di screp.ancies between - values for the same parameter recorded in different sections of the-procedures, examples of data not being recorded, and a suspect xenon value in the May 20, 1988, ECP calculation. None of the identified deficiencies appeared to invalidate the outcome of the procedure being performed. The reactor engineer promptly initiated corrective actions, including reporting to his management that the discrepancies possibly indicated inadequate reviews of the completed procedure At the time of the . inspection, procedure revisions were already in place to reduce such errors by requiring additional data to be recorded, and by providing more guidance. Due to the minimal actual safety significance of tne identified deficiencies, and the corrective action already taken by the_. licensee, per the provisions of the NRC enforcement policy this violation was not cited and will be tracked as LIV 327,328/88-60-04. No response to this item is required and the item is considered close The inspector discussed with licensee personnel the administrative 'f controls for computer programs being used to perform ECPs and other reactivity calculations. NQAM Part I Section 2.2.1, addressing - QA software, was implemented in part by Nuclear Fuels Procedure 8,

" Digital Computer Methods Control", and Methods Branch Instruction MBI 02, " Development or Modification and Release of Class.A and: Class B Computer Programs". The inspector noted marked improvement' in the licensee's control of nuclear engineering computer codes' relative' to previous inspections in this are ______ ---_ _ __ _

m

. .

.

.

The positive working relationship between licensee'and vendor nuclear engineering personnel noted by the NRC during the Unit I startup'wa also observed during this inspectio Biweekly phone conversations on core performance issues were being conducted, and included site, j corporate, and Westinghouse personnel.

l The . inspector concluded that the methods being used to predict ,

l critical boron concentrations were acceptable. The restart critical l boron discrepancies on both units appeared to1have resulted from a combination of . normal model . uncertainties, increased model uncertainties due to extended shutdown effects, and differences between the actual B-10 isotopic concentration and the value assumed in the nuclear design analysi IFI 327,328/88-53-02 remains open pending the resolution of other portions of the IFI which were not addressed in this report, Exit Interview (30703)

The inspection scope and findings were summarized on December 23, 1988, and on February 22, 1989, with those persons indicated in paragraph' The inspector described the areas inspected, and. discussed in detail'the inspection findings listed belo The' licensee acknowledged the inspection finding Proprietary material was ' reviewed during. the inspection, but was not retained by the inspecto Inspection Findings:

(0 pen)VIO 327,328/88-60-01: Failure to Promptly Identify and Initiate Adequate Corrective' Action for Conditions Adverse to Quality - Three Examples (Paragraph 2)

(0 pen)URI 327,328/88-60-02: QC Acceptance of Boric Acid which did not Conform to Receipt Specifications (Paragraph 2)

(0 pen)URI 327,328/88-60-03: Release ,of Boric Acid from Power Stores Prior to QC Inspection (Paragraph 2)

(Closed) LIV 327,328/88-60-04: Licensee-Identified Discrepancies in Completed ECP Procedures (Paragraph 2)

(0 pen)IFI 327,328/88-53-02: Followup on Issues Identified during Unit 1 Restart . Initial Criticalit (Paragraph 2) l List of Acronyms AI -

Administrative Instruction B -

Boron i BOC -

Beginning of Cycle i i

!

!

- _ _ - _ _ - _ __ - _ _ -

a

.__ _ _ _

.

.

CAQR - Conditions Adverse to Quality Report CBC - Critical Boron Concentration CFR -

Code of Federal Regulations CTS - Chemical Technical Support ECB -

Estimated Critical Boron (Concentration)

ECP -

Estimated Critical (Control Rod) Position EFPD - Effective Full Power Days HFP -

Hot Full Power HZP - Hot Zero Power IFI - (NRC) Inspector Followup Item NOV - N,tice of Violation NQAM - v' clear Quality Assurance Manual NRC - Nuclear Regulatory Commission NUPOP- Nuclear Parameters Operations Package OSP -

Office of Special Projects PCM -

Percent millitho PPM -

Parts per million QA -

Quality Assurance QC

-

Quality Control I RCS - Reactor Coolant System SI -

Surveillance Instruction TS -

Technical Specifications TVA - Tennessee Valley Authority l

'

URI - (NRC) I!nresolved Item VIO -

(NRC) Violation i

i

_____ - __ _ _______ __________ ( a- .

.

.

,

>4 !

.

_

_

_

_

,

1

1

-

x

-

_

.

._

4 .

_

1 _

_

_

-

)

-

U 2 T

N s 1 -_

_

O

.

/ D ' -

N

_

.

-

t (

-

..

P U

M

%~3 0

.

_

R 6 )

U 6 U B 9 g~

T -

1 1 E t

/

L 3 C 2 -

0. H D Y ' t

C C T

( -

S E U D P

.

' U S . _

R I N _

.

E R _

.

V R _

F . 0. BU -

N 6 O

R O

r k ,

B p N D 6 _

_

E a R

U  %&T .

S -

.

.

_

_

.

.

R E

F

_

s fa N -

-

_

_

_

_

.

_

g,- 2

_

a

.

.

ui ak-A_

i i .

o _ ~

- . o

-

i ROP" q8g mi8 c 9$ R$ 98 9a e @- - 5 $ d 5 a z 0 '"

E l .llt