Information Notice 1988-63, High Radiation Hazards from Irradiated Incore Detectors and Cables

High Radiation Hazards from Irradiated Incore Detectors and Cables

ML031150198
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, 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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	08/15/1988
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-88-063, NUDOCS 8808090264
Download: ML031150198 (12)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 August 15, 1988 NRC INFORMATION NOTICE NO. 88-63: HIGH RADIATION HAZARDS FROM IRRADIATED

INCORE DETECTORS AND CABLES

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors, research reactors and test reactors.

Purpose

This information notice is being provided to alert addressees to the recent

high exposure event at Surry Unit 2 resulting from the failure to adequately

evaluate the radiation hazards present during work involving irradiated incore

neutron detectors. Similar events have occurred at other facilities and are

summarized in Attachment 3. 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 do not constitute NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

On March 3, 1988, with Unit 2 at 100-percent power and the containment at

subatmospheric pressure, two instrument and control (I&C) technicians and one

health physics (HP) technician entered the Surry Unit 2 containment to free a

stuck incore detector and drive cable, transfer it to a storage location, and

replace the detector and associated drive cable with new equipment (see

Figure 1). According to the licensee's event investigation report, the "A"

detector cable became mechanically bound In the "B" 10-path transfer device

(the incore detector system was being operated in the "Emergency" mode at the

time because the "B" incore detector was inoperable). This resulted in the "A"

detector and cable being lodged in the core. The binding was a result of the

10-path transfer device becoming misaligned when the 10-path transfer device

attempted to rotate to the next core thimble position while the cable was still

inserted in the previous core thimble location. The bound cable could not be

electrically retracted from the core.

During efforts to dislodge the detector, about 100 feet of the cable attached

to the detector were manually pulled into the Seal Table Room, through the

polar crane wall, and taken up on the "A"-drive-unit reel assembly in the outer

annulus area. As the incore detector was pulled Lip to the penetration through

890264 Z

IN 88-63 August 15, 1988 the crane wall (see Figure 2), the HP technician noted rapidly

radiation levels near the transfer tube which soon exceeded increasing

reading of his survey meter (1000 R/hr). He then ordered the the maximum onscale

work stopped and

the work platform evacuated. Dose estimates performed by

the licensee

that whole body coses for the three workers ranged from approximately show

mrem. The worker who held and pulled the cable received a 700-1000

his hand. The beta dose contribution to the workers was smalldose of 800 mrem to

stainless steel tube casing through which the activated drive because the

inserted effectively attenuated the beta radiation. cable was

Subsequent licensee and NRC regional review of the event

revealed several key

factors that contributed to the incident.

1. Failure To Adequately Evaluate the Radiation Hazards Present

on an Incore Detector During Work

Licensee personnel had freed stuck detectors several times

Radiation levels associated with the detector typically ranged in the past.

and 35 R/hr; the drive cable had never exhibited significant between 5 activity. The principal radionuclide of concern in the drive induced

at Surry is manganese-56, which has a half-life of 2.56 hours6.481481e-4 days <br />0.0156 hours <br />9.259259e-5 weeks <br />2.1308e-5 months <br /> cables used

accounts for 99 percent of the dose rate once it has reached and which

in the core. (NOTE: the principal radionuclide of concern equilibrium

depending on drive cable composition and core irradiation/decay may vary

The reason for the typically low activity levels of the drive time.)

past at Surry is that either the cable had resided in the cable in the

short time or that it was allowed to decay to background core for only a

levels between

the time it was removed from the core and the time it was withdrawn

the Seal Table Room. However, in this event, the drive cable into

been in the core at 100-percent power for 26 days) had decayed (which had

minutes before being withdrawn through the Seal Table Room for only 15 annulus area and, therefore, was highly radioactive. The into the outer

to evaluate the radiation hazards from the drive cable and licensee failed

several feet of

activated cable were manually pulled into the outer annulus

the HP technician halted work and ordered all personnel out area before

Survey meter readings of more than 1000 R/hr were measured of the area.

12 inches from

the cable.

2. Use of Inadequate Procedures With Insufficient Radiological

Controls

Because no special procedure was available for freeing the

detector, the licensee wrote a temporary change to the normal stuck incore

for replacing the detector to cover this operation. This procedure

did not offer any precautions about assessing the detector's procedure change

stay time (irradiation time) in the core or the resultant location and

detector or

cable radiation levels. It also did not contain any stop-work

based on measured radiation levels or steps to permit withdrawallimitations

detector through the Seal Table Room and up to the polar of the

crane wall.

IN 88-63 August 15, 1988 Finally, this procedure did not have any requirements for using extremity

dosimeters while manually retracting the drive cable. If this procedure

had been formally reviewed (as is required by the licensee's Technical

Specifications when the purpose of the procedure is changed), the radio- logical controls described above might have been included.

3. Lack of Communication Among Individuals and Work Groups

Performance of this job under a Standing Radiation Work Permit (RWP)

instead of under a Special RWP allowed the job to be carried out without

prior review by Health Physics personnel or establishment of special

radiological controls. The HP technician covering the job did not receive

an adequate pre-job briefing and was not provided with sound-powered

headphones to communicate with the control room during the job, as were

the other two technicians performing the work. Therefore, he was not

aware of the detector's location as it was being withdrawn. In addition, dil three individuals performing the work were wearing respirators (be- cause of reduced oxygen in the subatmospheric containment), further

hindering communications among the members of the work party.

As a result of this event, the licensee has initiated certain corrective

actions which include the following:

(a) Revision of the procedure to replace incore detectors to include steps to

free stuck detectors. Performance of this procedure will require the

approval of the HP Shift Supervisor, the use of a Special RWP, limitations

on manual withdrawal of the detector drive cable, and an evaluation of

radiological hazards and detector location.

(b) Revision of appropriate training programs and procedures to incorporate

the lessons learned from this event.

(c) Informing appropriate station personnel of the key points and lessons

learned from this event.

Discussion:

Irradiated components, such as incore flux detectors and attached drive cables, can create radiation fields in which permissible occupational dose standards

can be exceeded in less than a few seconds and acute exposures, sufficient to

cause serious radiation injury, are possible with just several minutes of

exposure. The event at Surry and a similar incident involving the manual

freeing of a stuck incore detector at Indian Point 3 in 1980 were both the

result of the licensee's failure to evaluate the radiation hazard from the

neutron activation of the incore flux detector drive cable. In both cases, the

irradiated drive cable itself, which had not been allowed to decay sufficiently

after being removed from the core, was the contributing factor to the high

exposures at Surry and the overexposures at Indian Point.

IN 88-63 August 15, 1988 The Surry event is just one in a series of overexposures or near overexposures

in which a lack of management oversight led to inadequate radiological assess- ment and a resultant lack of proper control over work activities involving

irradiated components. Several NRC and Institute of Nuclear Power Operations

(INPO) generic communications have been issued over the last several years

informing licensees of the dangers involved with entry into high radiation

areas (see Attachment 4). On June 13, 1988, the NRC issued a Notice of Viola- tion and Proposed Imposition of Civil Penalty in the amount of $100,000 for the

Surry event to emphasize the importance of using proper radiological procedures

in high radiation areas.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate

regional office.

~harlesE. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles S. Hinson, NRR

(301) 492-3148 Craig Bassett, RII

(404) 242-5570

Attachments:

1. Figure 1, Typical Westinghouse Incore Neutron Monitoring System

2. Figure 2, Relative Positions of Individuals During Incident

3. Related Event Summaries

4. Past Related Correspondence

5. List of Recently Issued NRC Information Notices

Attachment 1 IN 88-63 FIGURE 1 August 15, 1988 TYPICAL WESTINGHOUSE INCORE NEUTRON MONITORING SYSTEM Page I of I

Safety SwOtches r-I Drive

~ Units

Limit Switches _

Incore Neutron, Reactor Detector Cable

Vessel .nsfers

Incore Neutron

Thimble Tube Inq Detector Inside.

Fuel Assembl,: Thimble Tube

Guide Tube

Seals

High-Pressure

Conduits *

ts'

Thimble Tubes Inside ,

High-Pressure Conduits

Detector

Drive -

Cable Incore

Neutron

10-Path {,Detector

Transfer

Device

Mechanical Seal Table

Seal .

Reacto

Vessel High- Pressure Conduit RCS Pressure

Thimble Tube Boundary

RCS Pressure

ort/ /

L

_

)

.

1)

Nu

J

IfA

_

mp.

-

//

I. I

Relative Positions of Individuals During Incident

Fve-Path Drive Unit

Transfer

Dw~ce

(

\etecor

a,,

C)

Withdrawn Umit

Switch

Crane Wag Actated portion of cable Is shown by the hash nwv

It D~1--

to C z

>

OQ OQ

M C 00

(Taken from the Virginia Power handout presented at the NRC Enforcement Conference. April 21, 1988, CO CD n

_ rt ,I

for the March 3, 1988 incident at Surry Power Station Unit 2)

oro

CO

ao

ld

Attachment 3 IN 88-63 August 15, 1988 Related Event Summaries

Overexposure of Workers Retrieving Stuck Incore Neutron Detector

(Indian Point 3, PWR)

Inspection

Report No.: 50-286/80-09 Event Date: 6/24/80

Event Cause: Lack of Maintenance Procedure

Abstract: When a problem developed with retrieval of a neutron flux

detector, two instrument and control (I&C) personnel and a

health physics (HP) technician entered the containment to

inspect and repair the moveable detector system. When it was

discovered that the drive cable was severed, the workers decided

to retract the cable by hand (without benefit of approved

procedural guidance). After withdrawing, cutting, and bagging

approximately 90 percent of the cable, the remaining 8-10 feet

of cable were extracted. The detector was cut off and put in a

shielded container; the remaining cable was bagged and set

between one of the I&C workers and the HP technician. When the

HP technician noticed that the dose rate above the bagged end

cable section was nearly 200 R/hr, he evacuated the area. This

incident resulted in quarterly exposures to the two I&C workers

of 4.2 and 4.1 rem whole body, 7.1 and 8.2 rem skin, and 43.7 and 17.1 rem extremity, respectively. One of the corrective

actions taken by the licensee to prevent a recurrence of this

event was the preparation of a procedure for removing and

replacing incore detectors.

Traversing Incore Probe (TIP) Room Entry (Vermont Yankee, BWR)

Inspection

Report No.: 50-271/85-21 INPO SER 50-85 Event Date: 8/8/85 Event Cause: Inexperienced HP Technician

Abstract: After a TIP probe had remained in the core at 90 percent power

for more than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> (because of a TIP drive power loss from a

shorted TIP ball valve solenoid), the probe was manually cranked

into its storage area inside the TIP room. Since a radiation

wfork permit (RWP) was required in order to enter the room to

Attachment 3 IN 88-63 August 15, 1988 repair the ball valve solenoid, a backshift HP technician

prepared to survey the area to gather information to fill out

the RWP. After notifying the shift supervisor, the HP techni- cian and an auxiliary operator entered the room. Using a

hand-held ionization chamber, the HP technician measured dose

rates near the door of 200 R/hr. The HP technician then pro- ceeded further into the room and measurea dose rates of

1000 R/hr near the core probes using a teletector. After the HP

technician noticed that his 0-500 mR dosimeter was offscale, the

two individuals left the room. The HP technician received 1.3 rem; the auxiliary operator received 270 mrem. The radiation

hazards of an activated TIP and cable were inadequately evaluat- ed because the HP technician had little experience on what

precautionary actions to take upon encountering the high expo- sure rates that existed in the TIP room. Among the corrective

actions taken by the licensee to prevent recurrence of this

event were issuance of procedures for TIP room entrance (includ- ing an RWP requirement for all entries), HP training on the

lessons learned from this incident, and installation of a TIP

room remote area radiation monitor.

Attachment 4 TN 88-63 August 15, 1988 Past Related Correspondence:

INPO Significant Event Report (SER) 6-88, "Uncontrolled Radiation Exposure,"

March 9, 1988.

IE Information Notice No. 86-44, "Failure To Follow Procedures When Working in

High Radiation Areas," June 10, 1986.

INPO Significant Event Report (SER) 50-85, "Uncontrolled Personnel Radiation

Exposure," November 4, 1985 (discusses two events).

INPO Significant Operating Experience Report (SOER) 85-3, "Excessive Personnel

Radiation Exposures," April 30, 1985.

Attachment 5 IN 88-63 August 15, 1988 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

88-62 Recent Findings Concerning 8/12/88 All holders of NRC

Implementation of Quality quality assurance

Assurance Programs by program approval

Suppliers of Transport for radioactive

Packages material packages.

88-61 Control Room Habitability - 8/11/88 All holders of OLs

Recent Reviews of Operating or CPs for nuclear

Experience power reactors.

88-60 Inadequate Design and 8/11/88 All holders of OLs

Installation of Watertight or CPs for nuclear

Penetration Seals power reactors.

88-04, Inadequate Qualification 8/9/88 All holders of OLs

Supplement 1 and Documentation of Fire or CPs for nuclear

Barrier Penetration Seals power reactors.

88-59 Main Steam Isolation Valve 8/9/88 All holders of OLs

Guide Rail Failure at or CPs for nuclear

Waterford Unit 3 power reactors.

88-58 Potential Problems with 8/8/88 All holders of OLs

ASEA Brown Boveri ITE-51L or CPs for nuclear

Time-Overcurrent Relays power reactors.

88-57 Potential Loss of Safe 8/8/88 All holders of OLs

Shutdown Equipment Due to or CPs for nuclear

Premature Silicon Controlled power reactors.

Rectifier Failure

88-56 Potential Problems with 8/4/88 All holders of OLs

Silicone Foam Fire Barrier or CPs for nuclear

Penetration Seals power reactors.

88-55 Potential Problems Caused 8/3/88 All holders of OLs

by Single Failure of an or CPs for nuclear

Engineered Safety Feature power reactors.

Swing Bus

OL = Operating License

CP = Construction Permit

IN 88-63 August 15, 1988 The Surry event is just one in a series of overexposures or near overexposures

in which a lack of management oversight led to inadequate radiological assess- ment and a resultant lack of proper control over work activities involving

irradiated components. Several NRC and Institute of Nuclear Power Operations

(INPO) generic communications have been issued over the last several years

informing licensees of the dangers involved with entry into high radiation

areas (see Attachment 4). On June 13, 1988, the NRC issued a Notice of Viola- tion and Proposed Imposition of Civil Penalty in the amount of $100,000 for the

Surry event to emphasize the importance of using proper radiological procedures

in high radiation areas.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles S. Hinson, NRR

(301) 492-3148 Craig Bassett, RII

(404) 242-5570

Attachments:

1. Figure 1, Typical Westinghouse Incore Neutron Monitoring System

2. Figure 2, Relative Positions of Individuals During Incident

3. Related Event Summaries

4. Past Related Correspondence

5. List of Recently Issued NRC Information Notices

• Transmitted by memo to C. H. Berlinger from L. J. Cunningham dated

June 30, 1988.

• SEE PREVIOUS CONCURRENCES

l *C/OGCB:DOEA:NRR

zIE~g~ti7LCH Berlinger

08A7 /88 08/09/88

• RPB:DREP:NRR *SC/RPB:DREP:NRR *C/RPB:DREP:NRR *PP B:ARM *OGCB:DOEA:NRR

CSHinson JEWigginton LJCunningham RFSanders PCWen

06/30/88 06/30/88 06/30/88 06/27/88 07/13/88

IN 88-XX

July xx, 1988 The Surry event is just one in a series of overexposures or near overexposures

in which a lack of management oversight led to inadequate radiological assess- ment and a resultant lack of proper control over work activities involving

irradiated components. Several NRC and Institute of Nuclear Power Operations

(INPO) generic communications have been issued over the last several years

informing licensees of the dangers involved with entry into high radiation

areas (see Attachment 4). On June 13, 1988, NRC issued a Notice of Violation

and Proposed Imposition of Civil Penalty in the amount of $100,000 for the

Surry event to emphasize the importance of using proper radiological procedures

in high radiation areas.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the regional administrator of the appropriate

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles S. Hinson, NRR

(301) 492-3148 Craig Bassett, RIu

(404) 242-5570

Attachments:

1. Figure 1

2. Figure 2

3. Related Event Summarles

4. Past Related Correspondence

5. List of Recently Issued NRC Information Notices

• Transmitted by memo to C. H. Berlinger from L. J. Cunningham dated

June 30, 1988.

• SEE PREVIOUS CONCURRENCES D/DOEA:NRR C/OGCYZA:NRR

DE:R D/88A-R

07 Cg/QG7/88 -N

k CERossi CHBerlinger

• RPB:DREP:NRI

e /07/ /88 Q08/1t88 A\*SC :uDREP:NRR RE:R *PPMB:ARM OGCB:DOEA:NqR

CSHinson Wigginton L ningham RSaeLde.> PCWen 1}%NJ

06/30/88 06/30/88 06/30/88 06/27/88 07/13/88