Information Notice 1996-69, Operator Actions Affecting Reactivity

Operator Actions Affecting Reactivity

ML031050475
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/20/1996
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-96-069, NUDOCS 9612160118
Download: ML031050475 (8)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 December 20, 1996 NRC INFORMATION NOTICE 96-69: OPERATOR ACTIONS AFFECTING REACTIVITY

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to operating events that have affected reactivity. It is expected that recipients will

review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not

NRC requirements; therefore, no specific action or written response is required.

Background

Generic Letter 85-05, "Inadvertent Boron Dilution Events," dated January 31, 1985, was used

to indicate the staffs position that resulted from the evaluation of Generic Issue 22,

"Inadvertent Boron Dilution Events." The generic letter considers an unmitigated boron

dilution event as a serious breakdown in the licensee's ability to control its plant and strongly

urges each licensee to assure itself that adequate protection against boron dilution events

exists in its plants. However, the consequences are not severe enough to warrant backfitting

requirements for boron dilution events at operating reactors.

In the past several years, this year in particular, there have been numerous events where

operator actions inappropriately affected reactivity. This information notice highlights several

recent events in which poor command and control during reactivity evolutions have led to

unanticipated conditions.

Description of Circumstances

Byron Unit I

On June 12, 1996, the licensee made four dilutions of the reactor coolant system. Only the

first dilution was calculated in advance. At the time, Byron Unit I was in cold shutdown for a

refueling outage. Fuel had been reloaded into the core, and the reactor head was in

position. The reactor coolant loops were isolated to support steam generator tube inspection

and repair. The reactor coolant system (RCS) boron concentration was 1,984 parts per

million (ppm). The RCS silica concentration was elevated at 4 ppm.

96121601 18 '\\

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IN 96-69 December 20, 1996 A series of dilutions was planned to reduce silica levels and bring the RCS boron

concentration closer to the 1,600 ppm starting point for the planned dilution to criticality. The

target RCS boron concentration was 1,700 ppm.

The operations staff added approximately 7,600 liters [2,000 gallons] of pure, unborated

water from the primary water storage tank through a feed-and-bleed dilution. A reactor

operator calculated the expected boron concentration after this dilution to be no less than

1,837 ppm. The subsequent chemistry sample results indicated a boron concentration of

1,942 ppm.

On the basis of the chemistry sample result, the reactor operators performed a second

dilution of 7,600 liters [2,000 gallons] without conducting formal calculations expecting to

achieve a boron concentration of around 1,800 ppm. The chemistry sample after the second

dilution indicated a boron concentration of 1,877 ppm. Based on this and a subsequent

chemistry sample, but without formal calculations, the reactor operators made two additional

dilutions of 15,200 liters [4,000 gallons] each, expecting a final boron concentration of greater

than 1,700 ppm. The chemistry sample results after the fourth dilution indicated a boron

concentration of 1,521 ppm. The reactor operators added borated water to increase the

boron concentration to about 1,585 ppm to ensure adequate shutdown margin. The

licensee's Technical Specifications require a 1.3-percent shutdown margin, which the

licensee indicated was about 1,164 ppm boron.

The licensee determined that the sample line was not adequately purged before the first

three samples were obtained. However, the sample valve was left open for about 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />

before the fourth sample was taken, which allowed the line to be adequately purged; thus a

representative sample was obtained.

Washington Nuclear Project No. 2

On June 27, 19°6, the reactor achieved criticality at Step 8-3 in the rod pull sequence.

Criticality was expected at Step 12-18 of the rod pull sequence, with an acceptable range of

achieving criticality (+/- 10 my,) between Steps 11-12 and 14-20. Achieving criticality at

Step 8-3 was outside the licensee's self-imposed acceptable range of values and was

approximately 16 mk,,,,,before the calculated estimated critical position. In accordance

with plant procedures, operators manually inserted control rods-to shut-down the reactor.

The estimated critical position calculated for the startup was performed using an

inappropriate parameter for the plant conditions. The nuclear engineer selected an incorrect

parameter for xenon dependence. The reactor was shutdown for a short period of time and

xenon did not completely decay and was incorrectly accounted for in the calculation.

During the approach to criticality, members of the control room staff were involved with

activities related to shift turnover, this may have distracted personnel involved with the

startup.

KY 11 IN 96-69 December 20, 1996 St. Lucie Unit 1 On January 22, 1996, while performing a routine manual boron dilution of the reactor coolant

system, the board reactor controls operator (RCO) was distracted leading to an over dilution

with reactor power reaching 101 percent. During the evolution the RCO responded to a

secondary plant annunciator and lost track of the routine dilution. He then requested to be

relieved by the desk RCO while he prepared his lunch. During the turnover, there was no

discussion of the dilution in progress which continued for seven minutes until the board RCO

returned and realized his error. The operators took prompt corrective action of stopping the

dilution and initiating manual boration.

Discussion

At Byron, an inadequate sampling procedure and inadequate calculations of boron

concentration led to an unexpected dilution of 179 ppm below the target boron concentration

of 1,700 ppm. The licensee determined the chemistry sample procedure to be deficient.

This deficiency was originally noted during review of procedures for post-accident sampling;

however, the chemistry staff failed to recognize the implications on routine sampling. The

licensee's dilution procedure was deficient, also, In that It did not have provisions for dilutions

with the loop stop isolation valves closed. The operators calculated the reduced volume for

the dilution calculations and attributed the differences in expected and sample boron

concentrations to the conservative reactor coolant system volume used in the calculation.

The reactor operators continued with successive dilutions based on the original calculation

and the sample concentrations but failed to adequately question the higher than expected

sample values and to perform acceptable calculations between dilutions in order to determine

the additional dilution amounts.

At Washington Nuclear Project No. 2, Shift Nuclear Engineers, because of inadequate

training on a recent software modification, incorrectly selected a parameter which resulted in

the wrong estimated critical position. These engineers and operators suspected a problem

with the estimated critical position but did not effectively resolve their concerns or express

them to higher management. The engineers did perform an independent verification which

confirmed the estimated value; however, they used the same software and input parameters.

During the startup, the control room staff realized that the reactor would go critical outside

their self-imposed +/- 10 mk,,,,. reactivity band; however, they continued the startup

because of their interpretation of a poorly written startup procedure. The likelihood of

achieving early criticality was not communicated to upper management, either. When

criticality was achieved, operators then acted conservatively and manually shut down the

reactor.

At St. Lucie Unit 1, the board RCO exhibited inattentiveness to a routine evolution affecting

reactivity. The RCO initiated the dilution without notifying other control room personnel and

failed to discuss the evolution in progress with his temporary replacement prior to exiting the

IN 96-69 December 20, 1996 control room. As a result, the senior reactor operator and the other operators were unaware

that a reactivity addition was taking place. Upon returning to the control room, the RCO

noted an alarm which was due to increasing reactor coolant system pressure, realized his

error, and took prompt corrective actions.

Both the Byron and the Washington Nuclear Project events involved a lack of questioning

attitude that would have allowed the operators to suspend the ongoing evolutions affecting

reactivity until they had an understanding of the unexpected plant indications. Furthermore, all three events contained inappropriate command and control over activities associated with

reactivity manipulations.

Additional details of these events can be found in the following inspection reports: Byron

Unit I IR 50-454/96-05; 50-455/96-05 dated July 31, 1996 [9608120029]; Washington

Nuclear Project No. 2 IR 50-397/96-16 dated September 12, 1996 [96091902751; and

St. Lucie IR 50-247/96-03 dated February 22, 1996 [96071502941.

This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

/Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: N. D. Hilton, Rill M. S. Miller, Ril

(815) 234-5451 (407) 464-7822 E-mail: ndh@nrc.gov E-mail: msm@nrc.gov

R. C. Barr, RIV S. S. Koenick, NRR

(509) 377-2627 (301) 415-2841 E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments: List of Recently Issued NRC Information Notices

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IN 96-69 December 20, 1996 control room. As a result, the senior reactor operator and the other operators were unaware

that a reactivity addition was taking place. Upon returning to the control room, the RCO

noted an alarm which was due to increasing reactor coolant system pressure, realized his

error, and took prompt corrective actions.

Both the Byron and the Washington Nuclear Project events involved a lack of questioning

attitude that would have allowed the operators to suspend the ongoing evolutions affecting

reactivity until they had an understanding of the unexpected plant indications. Furthermore, all three events contained inappropriate command and control over activities associated with

reactivity manipulations.

Additional details of these events can be found in the following inspection reports: Byron

Unit I IR 50-454/96-05; 50-455/96-05 dated July 31, 1996 [9608120029]; Washington

Nuclear Project No. 2 IR 50-397/96-16 dated September 12, 1996 [9609190275]; and

St. Lucie IR 50-247/96-03 dated February 22, 1996 [9607150294].

This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

original signed by D.B. Matthews

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: N. D. Hilton, Rill M. S. Miller, RII

(815) 234-5451 (407) 464-7822 E-mail: ndhenrc.gov E-mail: msm@nrc.gov

R. C. Barr, RIV S. S. Koenick, NRR

(509) 377-2627 (301) 415-2841 E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments: List of Recently Issued NRC Information Notices

Tech Editor has reviewed and concurred on 9/24/96 i

OFC TECH D:DRCH C:PECB:DRPM D:

CONTACT

S _AJ

NAME BABoger AEChaffee* a WI-

DATE 09/24/96 11/15196 12/12/96 1243,96 fi- - - - -. -p- k kis

[UMIC-NAL KtVUUKU WJTj

DOCUMENT NAME: 96-69.1N

IN 96- December , 1996 At St. Lucie Unit 1, the board RCO exhibited inattentiveness to a routine

evolution affecting reactivity. The RCO initiated the dilution without

notifying other control room personnel and failed to discuss the evolution in

progress with his temporary replacement prior to exiting the control room. As

a result, the senior reactor operator and the other operators were unaware

that a reactivity addition was taking place. Upon returning to the control

room, the RCO noted an alarm which was due to increasing reactor coolant

system pressure, realized his error, and took prompt corrective actions.

Both the Byron and the Washington Nuclear Project events involved a lack of

questioning attitude that would have allowed the operators to suspend the

ongoing evolutions affecting reactivity until they had an understanding of the

unexpected plant indications. Furthermore, all three events contained

inappropriate command and control over activities associated with reactivity

manipulations.

Additional details of these events can be found in the following inspection

reports: Byron Unit 1 IR 50-454/96-05; 50-455/96-05 dated July 31, 1996

[9608120029]: Washington Nuclear Project No. 2 IR 50-397/96-16 dated September

12, 1996 [9609190275]; and St. Lucie IR 50-247/96-03 dated February 22. 1996

[9607150294].

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: N. D. Hilton, RIII M. S. Miller, RII

(815) 234-5451 (407) 464-7822 E-mail: ndh@nrc.gov E-mail: msm@nrc.gov

R. C. Barr, RIV S. S. Koenick. NRR

(509) 377-2627 (301) 415-2841 E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments: List of Recently Issued NRC Information Notices

OFC TECH

CONTACT

S D:DRCH C:PECB:DRPM D:DR

NAME * BABoger* AEChaffee TMa rtin

DATE 09/24/96 11/15/96 t296 &s,

1fi S;iJ /-V96 LUFFICIAL RLLURU LUWYJ

DOCUMENT NAME: G:\SSK2\REACTIVE.RV3

~ i~ IN 96- December , 1996 This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: N. D. Hilton, Rill M. S. Miller, Ril

(815) 234-5451 (407) 464-7822 E-mail: ndh@nrc.gov E-mail: msmenrc.gov

R. C. Barr, RIV S. S. Koenick, NRR

(509) 377-2627 (301) 415-2841 E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments: List of Recently Issued NRC Information Noticed

) '/4/x

OFC TECH D:DRCH C:PECB:DRPM D:DRPM

CONTACT

S

NAME __ _ _ BABoger t AEChaffee TTMartin

DATE /R/96 -- F/ I/96 / /96 I //96

[OFFICIAL RECORD COPY)

DOCUMENT NAME: G:\SSK2\REACTIVE.RV3

. I,. . I .

Attachment

IN 96-69 December 20, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-68 Incorrect Effective Diaphragm 12/19/96 All holders of OLs

Area Values in Vendor Manual or CPs for nuclear

Result in Potential Failure power reactors

of Pneumatic Diaphragm

Actuators

96-67 Vulnerability of Emergency 12/19/96 All holders of OLs

Diesel Generators to Fuel or CPs for nuclear

Oil/Lubricating Oil Incom- power reactors

patibility

96-66 Recent Misadministrations 12/13/96 All U.S. Nuclear

Caused by Incorrect Cali- Regulatory Commission

brations of Strontium-90 Medical Use Licensees

Eye Applicators authorized to use

strontium-90 (Sr-90)

eye applicators

96-65 Undetected Accumulation 12/11/96 All holders of OLs

of Gas in Reactor Coolant or CPs for nuclear

System and Inaccurate power reactors

Reactor Water Level

Indication During Shutdown

96-64 Modifications to Con- 12/10/96 All holders of OLs

tainment Blowout Panels or CPs for nuclear

Without Appropriate reactors

Design Controls

OL = Operating License

CP = Construction Permit