ML19259D485

Environ Incident 50-289/74-7:on 740619,excessive Chlorine in River Discharge Water Violated Ets.Confusing Chlorine Regulator Controls Resulted in Personnel Error.Varying River Chlorine Content Contributed to Problem

ML19259D485
Person / Time
Site:	Three Mile Island
Issue date:	06/26/1974
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0110, GQL-110, NUDOCS 7910240752
Download: ML19259D485 (5)

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DATE CF DOC- DATE REC'D LTR TWX RPT OT!ER Metropolitan Edison Company Reading, Pennsylvania 19603 R. C. Arno ld 6-26-74 7-3-74 X TO: ORIG CC OTHER SENT AEC PDR X SENT LOCAL PDR X Mr. O'Re111v 1 d enna CLASS UNCLASS' PROP IIE0 INPlfT NO CYO REC'D DOCKET NO: XXXX 1 50-289 DESCRIPTION: ENCLOSURES: Ltr reporting Enviro Abnormal Occurrence [f]"7##'}.iNsL;;

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_ Bw fpgg l C f/.~ac., PowEn na snoGntss METROPOLITAN EDISON COMPANY PGOT CFFtCE BOX 542 PC?.OING, PENNSYLVANIA 19603 TELEPHONE 215 - 929-3601 June 26, 1974 GQL 0110 b" .: Mr. J. P. O'Reilly, Director p - Regulatory Operations Region 1 U. S. Atcmic Energy Cc= mission 631 Park Avenue King of Prussia, Pennsylvania 19h06

Dear Mr. O'Reilly:

Operating License DPR-50 Docket #50-289 In accordance with the Environmental Technical Specifications for Three Mile Island Nuclear Station, Unit 1, we are reporting the following Environnental Incident : (1) Reporting Numbert E.I. 50-289/Th-T (2a) Report Date: June 26, 1974 (2b) Occurrence Date: June 19, 197h (3) Facility: Three Mile Island Nuclear Generating Station, Unit 1 (h) Identification of Incident: 1459 195 Excessive Free Chlorine Concentratien at the Plant River Dischar_p_ vhich is a violation of Environmental Technical Specifications, paragrapn 2.2.la, and constitutes exceeding a limiting condition for operation. (5) Conditions Prior to Occurrence: Reactor critical, power escala-ticn test at 7"o of rated pcVer in progress with major plant para-meters as follows: . y p\.Y 9 Pcver: Core: Elec: 7". 0% V W CCCEIU g,

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Mr. J. P. O'Reilly June 26, 197h RC Pressure: 2155 psig RC Temperature: 556 F PRZR Level: 1h7 in. 0 FRZR Te=p.: 6h7 F (6) Description of Incident: During a periodic evolution conducted to chlorinate the systems cooled by the mechanical draft cocling tower, the plant river discharge samples taken 30 and 50 minutes after cen=ence=ent of the evolution indicated a free chlorine concentration of .115 and .125 ppm. Because the sample pu=p lost suction pressure, the 10-minute sa=ple was not taken. In that chlorine addition had been terminated about 15 minutes after cc==ence=ent of the evolution, it was determined that there were no additional actions which could be taken to get the reading within the specification limit. (7) Designation of Apparent Cause of Incident:

a. Persennel: Operation of the adjustment knob cn the chlorinator panel which controls the chlorine feed rate is confusing in that a clockwise turn of the knob decreases the feed rate and a counterclockwise turn increases it. This is contrary to most people's experience with such regulating devices, and in the present case it is kncvn that some of the chlorinator operators were unfamiliar with this equipment peculiarity.

Consequently, the chlorine feed rate may have been set higher than was intended.

b. Procedure: As an additional, possibly centributing factor, it should be recognized that there are no guidelines to aid in determining hev the chlorine feed rate should be varied as a function of existing conditions. So=e of the ccnditions which can affect the amount of free chlorine censumed as it passes through the syste=s include:

1. River cooling water transit time from the river cooling water pump discharge to the coolirs tower discharge, which is in turn a function of the number of syste=s anc pu=ps in use, and

2. Various river water conditions such as te=perature , pH, and organic ccmpositien. It is also possible that there is a randem variation in the concentration of chlcrine in the river water. Considering that in the present incident the values for chlorine in the discharge water are only slightly above the li=iting value of .10 ppm, even a 1cv concentration of chlorine in the pre-chlorinated water could be significant.

1459 196

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Mr. J. P. O'Reilly June 26, 1974

c. Material: The emperc=etric titration method used to teasure chlorine in the grab sa=ples is rather insensitive. In this method, the chlorine cencentration is determined directly frc=

the a=ount of titrant added. With the equipment that is available, it is not possible to adu a s=all enough drop of titrant to improve the instrument sensitivity beyond about

                 + .03 ppm. Also, because this analytical method relies en the visual detection of a slight needle fluctuation, it is likely that the actual value vill be exceeded by this amount in most cases. In the present instance, this could explain hev a value within specifications could appear to exceed the speci-fication limit.

(8) Analysis of Incident: It is believed that the level of free chlorine in the discharge water was not high enough and did not exist for a long enough period of time to have caused any enviren= ental damage or to have endangered the health and safety of the public. This belief is based on the following sigaificant points of information:

a. Chlorine addition was secured about 15 minutes before collec-tion of the 30-=inute sample.

b. Total chlorine in the 30- and 50-=inute grab sa=ples was measured as .115 and .125 pp=, respectively. All of these values are well belev the .20 pp= limit given in the Technical Specifications.

(9) Corrective Action: I==ediate corrective action involving ter=ina-tien of chlorine addition was not possible because chlorine addition had already been terminated by the time it was realized the limiting value for free chlorine vould be exceeded, and no other i==ediate actions were taken. The Station Superintendent was notified of the incident. He in turn infor=ed the Vice President-Generation and, to provide for an additional precautionary measure, it was then decided to decrease the chlorination feed rate to less than 150 lbs/ day prior to the next chlorination period. To ensure that those who use the chlorinator are familiar with the operation of the chlorine feed rate adjustment knob, a notice describing its proper use vill be posted in a conspicuous place on the chlorinator unit. Further, it has been decided to initiate sa=pling of the river intake water and the cooling water discharge prior to the cc==ence-

             =enu of the 0900 chlorination cycle, which is the chlorination cycle during which all of the incidents involving free chlorine have cecurred. It is believed that these additional sa=ples vill provide information en whether er not a detectable level of chlorine exists in the river water prior to chlorination.

1459 197

June 26, 197h Mr. J. F. O'Reilly -h-Additional long-term corrective acticns relating to this sane probles were stated in EI 50-289/7h-2 seven-day letter dated June 5, 1974, and EI 50-289/Th-3 seven-day letter dated June 12, 1974, and vill censist of:

a. reviewing a censultant's contract bid proposal submitted to Met-Ed to evaluate

1. if and how chlorine additice rates should be established as a function cf existing conditions, and

2. the reliability of the chlorine =cnitoring apparatus, and

b. utilizing the yet-to-be-established 90-day period referenced in the Environmental Technical Specifications, paragraph 2.2.1.b, to further evaluate (9)a.1. and (9)a.2. above.

(10) Failure Data:

a. Previous Failures: Although actual malfunctioning of the instru-ment used to measure chlorine in the grab samples is not believed to be the cause of this incident, this possibility has been previously noted in EI 50-289/Th-2 seven-day letter dated June 5, 197h; EI 50-289/7h-3 seven-day letter dated June 12, 197h; EI 50-289/Th-h seven-day letter dated June 13, 197h; and EI 50-289/7h-5 seven-day letter dated June 20, 197h.

b. Equip =ent Identification: It vill not be possible to ascertain if the =cnitoring apparatus failed until the additional tech-nical analyses centicned in (9)a. and (9)b. above are cct-pleted; however, en the basis of the information currently available, failure of the equipment is considered to be unlikely.

Sincerely, s - s ss t R. C. Ainold Vice President-Generatien RCA:JFV:sh ec: Directer Directorate of Licensing U. S. Atemic Energy Cc==ission Washington, D. C. 205h5 1459 198 File 20.1.1 7 7 3 11.1}}