ML20030D171
| ML20030D171 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/20/1981 |
| From: | Hovey G METROPOLITAN EDISON CO. |
| To: | Barrett L Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20030D172 | List: |
| References | |
| LL2-81-0198, LL2-81-198, NUDOCS 8108310473 | |
| Download: ML20030D171 (3) | |
Text
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,-eq-Metropolitan Edison Company -
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LI Middletown, Pennsylvania 17057 Writer's Direct Dial Number August 20, 1981 LL2-81-0198 s
TMI Program Office y
Attn:
Mr. L. H. Barrett, Deputy Program Director g
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U. S. Nuclear Regulatory Commission P
O c/o Three Mile Island Nuclear Station d
Middletown, Pennsylvania 17057 g
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Dear Sir:
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g 50 Three Mile Island Nuclear Station, Unit 2 (TMI-2) 3 E
Operating License No. DPR-73 Docket No. 50-320 Recovery Operations Plan Change Request No. 8 Reactor Coolant System Dissolved Hydrogen Level Enclosed please find the subject document. The submittal is made to request lowering the limit for dissolved hydrogen in the Reactor Coolant Sytem (RCS). This change will provide additional operational flexibility without having
...y adverse effect on the integrity of the RCS.
Sincerely,
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G. K. Hovey Vice-President and Director, TMI-2 GKH:RBS:djb
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Dr. B. J. Snyder, Program Director, TMI Program Office j,
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Operating License No. DPR-73 Docket No. 50-320 1.
Recovery Operations Plan Change Request No. 8 The licensee requests that the attached page 4.4-1 be substituted for the existing page 4.4-1 in the TML-II Recovery Operations Plan.
II.
Reason for Change This change is requested based on recent analyses of dissolved hydrogen levels in the RCS (Reactor Coolant System). The analyses have shown that the total dissolved hydrogen in the RCS has been decreasing.
Recent readings have averaged around 6 to 7 cc/kg dissolved hydrogen, with the long term trend showing a decrease to the 5 cch g limit.
Since the plant is basically in a stagnant condition with no reasonable means of adequately mixing chemistry control throughout the RCS, the 5 cc/kg dissolved hydrogen limit may become unachievable.
III.
Safety Evaluation Justifying Change Dissolved hydrogen is maintained in the RCS for control of corrosion via control of dissolved oxygen.
Studies were made with the MAKSIMA-CHEMIST computer program using input data shown in Table I that simulates the present plant conditions.
Equilibrium conditions were reached in 1200 seconds and the initial hydrogen concentration of I cc/kg declined slightly to an equilibrium concentration of 0.87 cc/kg. This means that a hydrogen residual of about 1 cc/kg is sufficient to control the oxygen with the present plant conditions and anticipated future plant conditions (i.e., as the core flux continues to decrease with time) as long as the oxygen in the fresh makeup is also controlled and a hydrazine residual is maintained in the fresh makeup. Makeup water is routinely controlled to less than 0.1 ppm by means of hydrazine addition. Test done weekly on RCS water indicate a dissolved oxygen content consistantly below 0.1 ppm.
The limit of 2 cc/kg dissolved hydrogen provides sufficient margin to ensure control of dissolved oxygen and thus corrosion.
Since the dissolved hydrogen limit is intended for oxygen control and since the proposed change h's been analyzed to show adequate control of dissolved a
oxygen, the licensee feels the proposed change has no safety significance.
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TABLE I MAKSIMA-CHEMIST INITIAL INPUT PARAMETERS.
Parameter Initial Oxygen Concentration, ppm 0.1 Initial Hydrogen Concentration, cc/kgm 1
pH 7.8 Makeup Flow, gpm 0.1 0xygen Concentration in Makeup, 6.63E-14(I}
Mole / Liter /Sec Hydrogen Concentration in Makeup, 3.31E-12(2)
Mole / Liter /Sec Dose Rate, eV/ Liter Sec 2.14E17 (I)Equivalet to 0.1 ppm 0 in Makeup Water 2
l-(2) Equivalent to 5 ppm N H in Makeup Water 24 l
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