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1750 Cheetant street Tower II

January 9, 1981

tir. J.*ess P. O'Emilly, DirectorU.S. iiuelear 2ngulatory Co-f amionOffice of Inepection and Enforcement |2egion II101 Marietta Street, Suite 3100Atlanta, Georgia 30303i

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Dear Mr. O'Reilly:

TAMESSEE VALLET AllIbORITY - SEQU0YAH WCLEAR PIET UNIT 1 - D0CIITNO. 50-327 - FACILITY OPEAATING LICCSE DPR-77 - SPECIAL 2EPORT do-6

The enclosed special report provides information concerning an inaavertantinjectics of Sodim-24 into the Sequoyah turbine ' uilding sump. Ihisoreport is suseitted in accordance with 10 CF2 20.405.

Very truly yours,

TEXWESSEE VALLZY AUTHORITY

H. J. GreenDirector of Maalaar Power

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Eaclaeureca (Easleemst):

Director (3)Office of Management Information and Program ControlU.S. Muelaar Assulatory Camelmaios'Jashington, D.C. 20555

Director (40)Offias of Inspectism and InforcementU.S. keelear Regulatory CommissismWash 4 -* . n.c. 20553 _/

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Mr. Bill Lavalleeihnelaar Safety Analysis Cantar agPale Alto, Califeraia 94303

NaC Inspector, Sequoyah

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REPORT ON DISCHARGE OF SODIUM-24 ,

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FROM SEQUOYAH NUCLEAR PLANT -l|

DECEMBER 1-2, 1980

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Report Prepared by - Douglas A. Fraser, Chemical Engineer

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J Date December 31, 1980 ,

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Summiary

This report discusses events which led up to the inadvertent, uncontrolleddischarge of a quantity of the radioactive tracer, sodium-24, during n teston December 1 and 2, 1980, and the action taken to mitigate the effectsof the discharge. The release was caused by inadequate test instructionsand poor communications between the radiochemical laboratory personnel ar.dthe test directors. No personnel received a measurable dose due to therelease, and no detectable radioactivity was released to the Tennesaae River.

Introductfen *

This report discusses the circumstances including the inadvert ent ar.d un-.

planned release of a quantity of radioactive sodium-24 from Sequoyah Juclear .

Plant during a plant steam generator carryover test conducted on Decembir 1and 2, 1980. The efforts made to mitigate the environmental effects of therelease are also presented.

Discussion

Sodium-24 is used as a radioactive tracer during steam generator moisturecarryover tests performed at various power icvels. A known concentrationof the element is injected into the steam generator feedwater, and the con-densate is monitored .'or the pre ence of sodium-24. By measuring the concen-tration of sodium-24 present in the condensate, the rate of moisture carryoverin the steam is calculated. It was during preparations for the carryover tectat 75% power that the sodium-24 was released from the plant.

Figure 1 is a simplified flow diagram of the system used for injection ofsodium-24 into the steam generator feedwater. A feed tank is connected bc3 weenthe sample line from feedwater heater IC-1 and the sample line from the fled-water header downstream of the feedwater isolation valve. The motive forcefar injecting the sodium-24 into the feedwater header is derived from thepressure drop across the feedwater faniscion valve.

During the injection process, valves VS-2, VS-3, VS-4, VS-6, and VC-2 areclosed. Valves VC-1, VS-1, and VS-5 are opened. The sodium-24 is depositedin the feed tank and valve VS-5 is closed. By opening valves VS-2 and VS-3,the pressure differential across the system causes the sodium-24 solution toficw into the feedwater header. The injection is verified by monitoring theradiation field around the feed tank.

Once the sodium-24 has been injected, valves VS-1, VS-2, and VS-3 are closed,and VS-6 is opened to drain the feed tank. Valvt VC-2 is then opened to allow

| the sample line from feedwater heater IC-1 to fl..sh. Val *es VA-1, VA-2, VB-1,| and VB-2 are also opened to flush the sample lines from feedwater heaters 1A-1| and 1B-1, respectively. Samples are then taken periodically from the feedwater- heaters 1A-1, IB-1, and IC-1 and analyzed to monitor levels of sodium-24 in the

water which has completed the thermal cycle.

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At approximately 2:30 p.m. , chemical laboratory personnel opened valves VA-1,VA-2, VB-1, VB-2, VC-1, and VC-2 to flush sample lines to obtain representa-tive samples in preparation for the test. The laboratory personnel werebriefed by the Nuclear Results Section personnel a't 4:30 p.m. to inform themof the sampling and analyses for which the laboratory would be responsible.This briefing did not include information on system design and flow paths tobe used during the test.

At approximately 5:30 p.m., the sodium-24 was received onsite (activity at4:30 p.m. was 0.96 Ci). The Nuclear Results Section personnel proceeded tosetup the system for injection of the sodium-24 solution. Personnel wereunaware that valve VC-2 was open (having been opened during the sample lineflushing operation) during the injection process. Valve VC-2 positioning

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did not appear in the step by step instructions but in a prerequisite state-*

ment. This resulted in the oversight of re-checking VC-2 position prior tothe eedium injection as the prerequisite was performed before laboratorypersonnel re-opened VC-2. The lack of a rpecific check-off for VC-2 and

was the cause of the incident.proper instructions to the laboratory personnel

When designated valves were opened at approxicately 8:15 p.m. (activity at,

8:15 p.m. was 0.798 Ci) to inject the sodium-24 frem the feed tank to thefeedwater header, the pressure from the header forced the sodium-24 solutionback through valves VS-2, 75-1, and VC-2 to the saeple sink, which drainedto the turbine building sump. The station sump pumps actuated on high waterlevel at approximately 10:55 p.m. , and the sodium-24 present caused theeffluent radiation monitor (0-RE-90-212) to alarm. The discharge lasted

approximately ten minutes and was routed to the yard drainage pond. Theyard drainage pond contents eventually reae.h the Tennessee River through .

the plant diffuser pond.

At 11:10 p.m., the discharge from the turbine buildit a surp was rerouted tothe unlined chemical cleaning pond for retention. All further sump dischargeswere routed to the unlined chemical cleaning pond.

Table 1 lists the calculated amount of sodium-24 discharged to the yard drainagepond and unlined chemical cleaning pond during the incident. Table II lists theconcentration of sodium-24 observed following the release. Attachment 1 providesa discussion of doses incurred as a result of this incident. Figure 2 shows therelationship between the turbine building sump, yard drainage pond, unlined pend,plant diffuser pond and the Tennessee River.

Conclusion.

This incident resulted directly f rom inadequate test instructions and impropercommunications between the test directors arm laboratory personnel. No personnelreceived measurable exposure as a result of this incident, and no detectableradioactivity was released to the Tennessee River. The test instructions havebeen clarified to avoid any similar misunderstanding of the instructions onfuture carryover tests.

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TABLE I

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ACTIVITY DISCHARGED TO PONDS *

Puspout Time Began, Time Ended Volume Curios _ Pond *

1 2255 2305 16000 gal 0.297 Ci . YDP

2 2345 0005 30000 gal 0.37 Ci UCP

3 0110 0120 11000 gal 0.068 Ci UCP -

4 0215 0247 22400 gal 6.93x10-3Ci UCP'

*YDP - Yard Drainage PondUCP - Unlined Chemical Cleaning Pond

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TABLE II*

SODIUM-24 CONCENTRATIONS FOLLOWING RELEASE. .

DATE TIME LOCATION SODIUM-24, uCi/ml

12/1/80 2320 TBS 3.27x10-32400 YPI 1.44x10-6

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2400 YPO ND

12/2/80 0215 YPI 8.71x10-70215 YPO ND

0315 YPI ND -

0315 YPO 1.71x10-50415 YPI ND

3.07x10-50415 YPO

0515 YPI ND

0515 YPO 4.36x10-50515 DF0 ND

0615 YPO 3.62x10-50615 YPO (West Bank) ND

0615 DP0 ND

0720 TBS 2.70x10-00745 YPO 3.20x10-50745 YPO (West Bank) ND

0745 DP0 ND50845 YPO 3.52x10 6

0845 YPO (West Bank 1.10x10-0845 DP0 ND

0945 YPO ND

0945 YPO (West Bank) 3.21x10-50945 DP0 ND1045 YPO (West Bank) ND

1045 DP0 ND

1145 YPO 1.75x10-51145 YPO (West Bank) 1.30x10-51145 DP0 ND

12/3/80 0600 TBS ND

0600 YPO ND0600 DP0 ND

0600 DP0 (West of YPO) ND

1000 UCP (East) 2.18x10-61000 UCP (South west) 2.66x10-61100 UCP (West) 2.63x10-6

12/4/80 0835 UCP ND

Key - TBS-Turbine Building SucpYPI-Yard Drainage Pond InletYPO-Yard Drainage Fond Outlet

| DPO-Diffuser Pond OutletUCP-Unlined Chemical Cleaning PondND-None Detected

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ATTACHMENT 1 |I

HP DATA DURING 24Na INJECTION AND FOLLOWUP |i

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At approximately 1730 hours on 12-1-80 a zone was erected on the north end of24Na source prior to injec-El 685 TB (TB = Turbine Building) to contain the

tion. This zone was posted as high radiation and contamination area.

Entry to the El 662.5 TB, U1 main steam valve rooms and the steam generatorblowdown tank / monitor area was prohibited by barricades. .

All source handling was performed behind a lead brick wall by personnel usingremote handling tools and extremity TLDs. All personnel involved wore thenormal TLD badge and self-reading dosimeter. .

Readings at the time of the injection were: 9R/hr y @l8", 4R/hry @3', no centactreading was made.

The injection pathway was conitored with no increase in levels indicated.During the inicial steam generator blowdcwn, continuous coverage was providedby HP with no radiaticn increase indicated.

At 2255 hrs, operations notified HP of an alarm on T.B. sump effluent radiationmonitor (0-RE-90-212). Investigation found 1 mrem /hr y G.A. around the sump and -

monitor. At 2310 hrs. HP escorted a chem lab analyst to sample the T.B. sumpwater. The one aiter sample read 0.5 mrem /hr y @ contact. A dose rate measure-mentwasmadeatthesumpwateryevel, indicating 10 mrem /hry. Chemistry'sanalysis showed 3.27E-3 pCi/ml Na, .

At 2340 hrs operations notified HP that the sump water was being pumped intothe unlined pond. HP supervision was notified.

roximately 0015 hrs, 12-2-80, HP initiated a survey tracing the path ofAtapgNafromtheinjectionpointtotheT.B. sump.the Z A 20' section of drai-

24trough below the chemiccl station El 685 up to the Na injection zone indicatedreadings of 1.0 to 1.C nten/hr y on the grating = 1' above water level. 3.0mrem /hr y was indicated at water level. The trough was zoned at this time. Waterwas flowing continuously in this area, going directly into the T.B. sump.

The path from the sump :o the pond was traced with the following results:

Pipe at sump 2.0 mrem /hr yPipe on El 685 2.0 mrem /hr yPipe leaving UII to ponds 1.0 mrem /hr yStorm drain at UII wall 3.0 mrem /hr yPipe at unlined pond during pumping 0.2 mrem /hr yWater in unlined pond = 60' from inlet pipe showed indications of low levelradiation with an RM 14 survey meter.

The storm drain was immediately zoned as a regulated area.

) At 0130 hrs the El 662.5 T.B. was cleared except for the sump area itself. The| steam generator blowdown area El 685 was cleared.

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At approximately 0700 hrs a followup survey from the sump was performed.

Pipe at sump 0.1 mrem /hr yPipe on El 685 < 0.1 mrem /hr yPipe leaving UII wall to ponds < 0.1 mram/hr yStorm drain to ponds 0.2 mrem /hr yPipe at unlined pond 0.15 mrem /hr y .

Water in unlined pond showed no detectable activity with an RM 14.

The storm drain was cleared at this time..

Per Title 10 Code of Federal Regulations - Part 20.405 a written report isrequired when radiation levels in a restricted area exceed any applicablelimit or when radiation levels in an unrestricted area exceed by ten timesany' applicable limit set forth. These levels were not exceeded.

Per 10CFR20.105 (B) the radiation level limits for an unrestricted areawere met or exceeded on the UII pipe, the storm drain and the pipe outsideUII going to the ponds. The UII piping read 2.0 mrem /hr at contact but islocated near the ceiling off El 685 and is not rer 'ily accessible. Readings3 foot above floor level were 0.3 mrem /hr y.

The storm drain read 3.0 mrem /hr y at contact with the water level in thebottom. This drain was posted immediately.

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The piping outside UII going to the ponds read 2.0 mrem /hr y at contact.

These areas existed for a total period of less than 8 hours (2255 hrs., 12-1-80/0700 hrs. ,12-2-80) . During this time there were no personnel present and noindividual received exposure. Public safety personnel were stationed at the

24holdup pond to prevent unauthorized entry of personnel in the area until the Nahad decayed to non detectable limits.

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NRC FQRM 366 U. S. NUCLEAR REGULATORY COMMISSION

(7 77)LICENSEE EVENT REPORT-

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' CONTROL BLOCK: | | | | | | | (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)1 6

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h1012| | |

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PERSONNEL EXPOSURESNOV8ER TYPE DESCRIPTION

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LOSS OF OR DAMAGE TO FACILITY gTYPE DESCRIPTION \

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NAME OF PREPARER PHONE: $'