ML19341A022

RO 80-6 on 801201 & 02:Na-24 Was Inadvertently Injected Into Turbine Bldg Sump.Caused by Inadequate Test Instructions & Poor Communications Between Test Directors & Radiochemical Lab Personnel

ML19341A022
Person / Time
Site:	Sequoyah
Issue date:	01/09/1981
From:	Fraser D, Green H TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
RO-80-6, NUDOCS 8101210466
Download: ML19341A022 (10)

Text

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. -: s ~~ - :t 1 1750 Cheetant street Tower II January 9, 1981 tir. J.*ess P. O'Emilly, Director U.S. iiuelear 2ngulatory Co-f amion Office of Inepection and Enforcement l 2egion II 101 Marietta Street, Suite 3100 i

Atlanta, Georgia 30303

Dear Mr. O'Reilly:

TAMESSEE VALLET AllIbORITY - SEQU0YAH WCLEAR PIET UNIT 1 - D0CIIT NO. 50-327 - FACILITY OPEAATING LICCSE DPR SPECIAL 2EPORT do-6 The enclosed special report provides information concerning an inaavertant injectics of Sodim-24 into the Sequoyah turbineo' uilding sump. Ihis report is suseitted in accordance with 10 CF2 20.405.

Very truly yours, TEXWESSEE VALLZY AUTHORITY H. J. Green Director of Maalaar Power l

Eaclaeure ca (Easleemst):

Director (3)

Office of Management Information and Program Control U.S. Muelaar Assulatory Camelmaios

'Jashington, D.C. 20555 Director (40)

Offias of Inspectism and Inforcement U.S. keelear Regulatory Commissism Wash 4 -* . n.c. 20553 _/i I

Mr. Bill Lavallee ihnelaar Safety Analysis Cantar ag Pale Alto, Califeraia 94303 NaC Inspector, Sequoyah 820moqn .- .. . , .

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l I REPORT ON DISCHARGE OF SODIUM-24 ,

9 FROM SEQUOYAH NUCLEAR PLANT -

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Report Prepared by - Douglas A. Fraser, Chemical Engineer l

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Date December 31, 1980 ,

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Summiary This report discusses events which led up to the inadvertent, uncontrolled discharge of a quantity of the radioactive tracer, sodium-24, during n test on December 1 and 2, 1980, and the action taken to mitigate the effects of the discharge. The release was caused by inadequate test instructions and poor communications between the radiochemical laboratory personnel ar.d the test directors. No personnel received a measurable dose due to the release, 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 1 and 2, 1980. The efforts made to mitigate the environmental effects of the release are also presented.

Discussion Sodium-24 is used as a radioactive tracer during steam generator moisture carryover tests performed at various power icvels. A known concentration of 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 carryover in the steam is calculated. It was during preparations for the carryover tect at 75% power that the sodium-24 was released from the plant.

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

During the injection process, valves VS-2, VS-3, VS-4, VS-6, and VC-2 are closed. Valves VC-1, VS-1, and VS-5 are opened. The sodium-24 is deposited in 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 to ficw into the feedwater header. The injection is verified by monitoring the radiation 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 l the sample line from feedwater heater IC-1 to fl..sh. Val *es VA-1, VA-2, VB-1, l and VB-2 are also opened to flush the sample lines from feedwater heaters 1A-1 l 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 were briefed by the Nuclear Results Section personnel a't 4:30 p.m. to inform them of the sampling and analyses for which the laboratory would be responsible.

This briefing did not include information on system design and flow paths to be used during the test.

At approximately 5:30 p.m., the sodium-24 was received onsite (activity at 4:30 p.m. was 0.96 Ci). The Nuclear Results Section personnel proceeded to setup the system for injection of the sodium-24 solution. Personnel were unaware that valve VC-2 was open (having been opened during the sample line flushing operation) during the injection process. Valve VC-2 positioning 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 to the eedium injection as the prerequisite was performed before laboratory personnel re-opened VC-2. The lack of a rpecific check-off for VC-2 and proper instructions to the laboratory personnel was the cause of the incident.

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 the feedwater header, the pressure from the header forced the sodium-24 solution back through valves VS-2, 75-1, and VC-2 to the saeple sink, which drained to the turbine building sump. The station sump pumps actuated on high water level at approximately 10:55 p.m. , and the sodium-24 present caused the effluent radiation monitor (0-RE-90-212) to alarm. The discharge lasted approximately ten minutes and was routed to the yard drainage pond. The yard 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 to the unlined chemical cleaning pond for retention. All further sump discharges were routed to the unlined chemical cleaning pond.

Table 1 lists the calculated amount of sodium-24 discharged to the yard drainage pond and unlined chemical cleaning pond during the incident. Table II lists the concentration of sodium-24 observed following the release. Attachment 1 provides a discussion of doses incurred as a result of this incident. Figure 2 shows the relationship 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 improper communications between the test directors arm laboratory personnel. No personnel received measurable exposure as a result of this incident, and no detectable radioactivity was released to the Tennessee River. The test instructions have been clarified to avoid any similar misunderstanding of the instructions on future carryover tests.

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TABLE I ACTIVITY DISCHARGED TO PONDS

• Time Ended Volume Curios _ Pond

• Puspout Time Began, 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 Pond UCP - Unlined Chemical Cleaning Pond

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i TABLE II SODIUM-24 CONCENTRATIONS FOLLOWING RELEASE DATE TIME LOCATION SODIUM-24, uCi/ml 12/1/80 2320 TBS 3.27x10-3 2400 YPI 1.44x10-6

• 2400 YPO ND 12/2/80 0215 YPI 8.71x10-7 0215 YPO ND 0315 YPI ND -

0315 YPO 1.71x10-5 0415 YPI ND 0415 YPO 3.07x10-5 0515 YPI ND 0515 YPO 4.36x10-5 0515 DF0 ND 0615 YPO 3.62x10-5 0615 YPO (West Bank) ND 0615 DP0 ND 0720 TBS 2.70x10-0 0745 YPO 3.20x10-5 0745 YPO (West Bank) ND 0745 DP0 ND 5

0845 YPO 3.52x10 1.10x10-6 0845 YPO (West Bank 0845 DP0 ND 0945 YPO ND 0945 YPO (West Bank) 3.21x10-5 0945 DP0 ND 1045 YPO (West Bank) ND 1045 DP0 ND 1145 YPO 1.75x10-5 1145 YPO (West Bank) 1.30x10-5 1145 DP0 ND 12/3/80 0600 TBS ND 0600 YPO ND 0600 DP0 ND 0600 DP0 (West of YPO) ND 1000 UCP (East) 2.18x10-6 1000 UCP (South west) 2.66x10-6 1100 UCP (West) 2.63x10-6 12/4/80 0835 UCP ND Key - TBS-Turbine Building Sucp YPI-Yard Drainage Pond Inlet YPO-Yard Drainage Fond Outlet l DPO-Diffuser Pond Outlet UCP-Unlined Chemical Cleaning Pond ND-None Detected I

I ATTACHMENT 1 l I

HP DATA DURING 24Na INJECTION AND FOLLOWUP l i

At approximately 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> on 12-1-80 a zone was erected on the north end of El 685 TB (TB = Turbine Building) to contain the 24Na source prior to injec-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 generator blowdown tank / monitor area was prohibited by barricades. .

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

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

The injection pathway was conitored with no increase in levels indicated.

During the inicial steam generator blowdcwn, continuous coverage was provided by HP with no radiaticn increase indicated.

At 2255 hrs, operations notified HP of an alarm on T.B. sump effluent radiation monitor (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. sump water. The one aiter sample read 0.5 mrem /hr y @ contact. A dose rate measure-mentwasmadeatthesumpwateryevel, indicating 10 mrem /hry. Chemistry's analysis showed 3.27E-3 pCi/ml Na, .

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

roximately 0015 hrs, 12-2-80, HP initiated a survey tracing the path of AtapgNafromtheinjectionpointtotheT.B.

the Z sump. A 20' section of drai-trough below the chemiccl station El 685 up to the 24 Na injection zone indicated readings of 1.0 to 1.C nten/hr y on the grating = 1' above water level. 3.0 mrem /hr y was indicated at water level. The trough was zoned at this time. Water was 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 y Pipe on El 685 2.0 mrem /hr y Pipe leaving UII to ponds 1.0 mrem /hr y Storm drain at UII wall 3.0 mrem /hr y Pipe at unlined pond during pumping 0.2 mrem /hr y Water in unlined pond = 60' from inlet pipe showed indications of low level radiation 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 l 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 y Pipe on El 685 < 0.1 mrem /hr y Pipe leaving UII wall to ponds < 0.1 mram/hr y Storm drain to ponds 0.2 mrem /hr y Pipe 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 is required when radiation levels in a restricted area exceed any applicable limit or when radiation levels in an unrestricted area exceed by ten times any' applicable limit set forth. These levels were not exceeded.

Per 10CFR20.105 (B) the radiation level limits for an unrestricted area were met or exceeded on the UII pipe, the storm drain and the pipe outside UII going to the ponds. The UII piping read 2.0 mrem /hr at contact but is located near the ceiling off El 685 and is not rer 'ily accessible. Readings 3 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 the bottom. This drain was posted immediately.

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 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> (2255 hrs., 12-1-80/

0700 hrs. ,12-2-80) . During this time there were no personnel present and no individual received exposure. Public safety personnel were stationed at the holdup pond to prevent unauthorized entry of personnel in the area until the Na 24 had decayed to non detectable limits.

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