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Progress of the Zinc Injection in Tsuruga NPP Unit 2

Nobuaki NAGATA, Hideaki ICHIGE, Eiichi KADOI. Progress of the Zinc Injection in Tsuruga NPP Unit 2. October 12, 2006. THE JAPAN ATOMIC POWER COMPANY. HOKKAIDO ELECTRIC POWER CO., INC. Yoshifumi WATANABE. THE KANSAI ELECTRIC POWER CO., INC. Hideya IKOMA. SHIKOKU ELECTRIC POWER CO., INC.

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Progress of the Zinc Injection in Tsuruga NPP Unit 2

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  1. Nobuaki NAGATA, Hideaki ICHIGE, Eiichi KADOI Progress of the Zinc Injection in Tsuruga NPP Unit 2 October 12, 2006 THE JAPAN ATOMIC POWER COMPANY HOKKAIDO ELECTRIC POWER CO., INC. Yoshifumi WATANABE THE KANSAI ELECTRIC POWER CO., INC. Hideya IKOMA SHIKOKU ELECTRIC POWER CO., INC. Tsuyoshi SEMBA SHIKOKU RESEARCH INSTITUTE INC. Toshiaki HAMAGUCHI

  2. Objectives To evaluate followings of the zinc injection for Japanese PWR plants by using Tsuruga-2 • Effect of water chemistry during zinc injection • Effect of decreasing dose equivalent rate on primary equipment and pipes after zinc injection • Evaluation of the fuel performance by observing the external appearance and thickness of oxide film on the fuel installed in core during zinc injection

  3. Outer layer （Ferrite） ： NiFe2O4 Inner layer （Chromite:CoCr2O4 ） :Zinc : Oxygen :Co,（Ni） : Cr General idea for dose reduction by application of Zn injection Primary Water Redeposition 58Co, 60Co Zn 58Co, 60Co Pipe Pipe Deposition Accumulation Zn Co Fuel Radioactivation Ni （ ） Zn Zn Accumulation and radioactivation of the corrosion products Suppression of the dissolution of corrosion products Suppression of redeposition Isotope Abundance (%) Radio Isotope Radioactive Half-life Zn-64 48.6 Zn-65 244 D Zn-66 27.9 － － Isotope Abundance(%) Zn-67 4.1 － － Zn-68 18.8 Zn-69 56 M Zn-69m 13.8 H Natural Zn Depleted Zn Zn-70 0.6 Zn-70m 4 H Depleted Zn : Suppression of dose increase due to reducing the abundance of Zn-64 below 1%

  4. The Application Study Schedule of Zn Injection FY 2006 FY 2004 FY 2005 22/4～22/5 15/12～25/2 Outage (Tsuruga-2) # 14 # 15 Depleted Zn Purchase Zn Injection Equipment designing, manufacturing, setting Planning and Pre-adjustment Start of Zn Injection(10/8) ▼ Zn Injection Evaluation Water Chemistry Dose equivalent rate Fuel Performance

  5. Steam generator (SG) Pressurizer Sampling rack Zinc acetate tank Demineralizer ※ Sample Water Return Injection Pump Zn injection equipment ※ Volume control tank (VCT) Reactor vessel Charging pump Primary Loop Chemical Volume Control System Sampling Room for Primary Water Zinc Injection System in Tsuruga-2 Tsuruga-2 4 loops PWRStart Operation : Feb. 1987 Electric Power : 1160 MWe

  6. Connection Point Zn Injection Equipment Equipment Configuration ・Chemical Tanks : 2 (10 little) ・Concentration of Zinc Acetate : about 5～12（g/little） Safety Precaution ・Chemical tank : low level detection ・injection pressure : high detection ・Leakage : detection ・check valve in sampling sink Automatic stop Chemical Tanks Drain Line Zn Injection Equipment Sampling Sink Zn Injection Equipment Zn injection equipment was downsized with making consideration to safety precaution, and was connected to the sampling return line.

  7. 10 Outage #15 9 8 About 7 ppb Start of Zn Injection 7 6 About 5 ppb 5 4 3 2 1 Detection Limit : １ｐｐｂ 0 May, 2005 Jul., 2005 Aug., 2005 Nov., 2005 Jan., 2006 Mar., 2006 May, 2006 Zn Injection Plan Zi Concentration in Primary Water (ppb) Incubation Period ※ Zn injection had been performed in Tsuruga-2 for eight months within a range of 5-7 ppb based on the European experience. (Upper limit : 10 ppb) ※Because most of the Zinc is incorporated in the oxide layers on primary equipment and piping , zinc concentration of primary water is not detected in a early stage of Zn injection.

  8. Start of Zn Injection Electric Power (Mwe) #14 Operation cycle #15 Operation cycle Zinc Ion Concentration (ppb) pH Conductivity pH (-) Cond. (μS/cm2) Co-58 Ion Concentration (Bq/ml) Co-60 Ion Primary Water Chemistry during the Zn Injection Although concentration of the radioactive Co was increased by a factor of ten with Zn injection than before, the increase was expected based on the European experience. RCS purity, pH and conductivity, was not affected.

  9. Measurement of the Radioactive Zinc(Verification of the depleted Zinc) 100 #14 Operation Cycle #15 Operation Cycle 10 Start of Zn Injection 1 Activity Concentration (Bq/ml) 0.1 0.01 Zn- 65 Crud Zn- 69m Crud Zn- 65 Ion Zn- 69m Ion 0.001 14/1/04 13/4/04 12/7/04 10/10/04 8/1/05 8/4/05 7/7/05 5/10/05 3/1/06 3/4/06 The increase in Zn-65 was not found due to using depleted zinc.

  10. Regenerative heat exchanger (0.3) Steam generator (SG) Hot leg (0.73) Nonregenerative heat exchanger (1.1) Sampling Rack Zinc Acetate Tank Demineralizer ＊ SG channel head (0.64 - 0.78) Volume control Tank (VCT) Sample water return Injection Pump ＊ Zn injection equipment Crossover leg (0.69) Reactor Vessel Charging pump RCS pump (0.86) Cold leg (0.81) : Dose rate measuring points (Ratio from the previous outage） Relative dose equivalent rate on the primary equipment and pipes The zinc injection reduced the dose rate of primary equipment and pipes to 70-80 % than that of previous outage. This effect of dose reduction is higher than expectation based on the foregoing plants. However, low temperature nonregenerater had no effect due to zinc injection.

  11. Behavior of dose equivalent rate in SG Channel head Zn Injection 100 SG channel head (Hot) 90 SG channel head (Cold) 80 70 ※ 60 50 Dose equivalent rate (mSv/h) 40 30 20 10 ※：Radiation source decay due to unscheduled plant shutdown when dose rate was measured 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Outage # Dose equivalent rate in SG channel head had increased with age, but was reduced to its about 20-30% thanks to the application of zinc injection.

  12. R P N M L K J H G F E D C B A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Evaluation of the Fuel Cladding- Visual Inspection of the fuel external appearance- Fuel experienced Zn injection Fuel experienced no Zn injection #13 Operation Cycle Fuel Burn-up : 13202MWd/t Specific Power ratio : 0.84 #13 Operation Cycle (Zn Injection) Fuel Burn-up : 46365MWd/t Specific Power ratio : 1.00 #14 Operation Cycle Fuel Burn-up : 31265MWd/t Specific Power ratio : 1.15 # R 08(46365MWd/t) # P 02 (46560MWd/t) Fuel surface showed no significant differences with or without zinc injection. (The region looked white on the figure due to difference of growth of the oxide film (thickness, crystal structure) does not show an abnormality for the fuel performance.)

  13. 160 * ( ) 11 財 原子力発電技術機構、平成 年度 軽水炉改良技術確証試験 Past Data ※ 12 3 （高燃焼度等燃料に関するもの）に関する報告書、平成 年 月 従来ｽｽﾞｼﾞﾙｶﾛｲｰ4 ** ( ) 10 財 原子力発電技術機構、平成 年度 軽水炉改良技術確証試験 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (先行照射) 140 11 3 （高燃焼度等燃料に関するもの）に関する報告書、平成 年 月 Past database ※ 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (Vandellos 2) * 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (North Anna 1) 120 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (高浜３号機) ** 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (敦賀２号機；亜鉛経験なし) 100 低ｽｽﾞｼﾞﾙｶﾛｲ-4 (敦賀２号機；亜鉛経験あり) : Zircaloy-4 (No Zn injection) Thickness of oxide film (μm) 80 : Zircaloy-4 (Zn injection) 60 40 20 ：Slightly rough surface 0 10 20 0 30 40 50 60 70 0 Average of fuel burn-up(GWd/t) ※Sendo et al. AESJ, 2003，Mitsubishi Heavy Industrial,LTD, NHI-NES-1012 Evaluation of the Fuel Cladding- Measured thickness of oxide film - In the result of the evaluation, it was not considered that zinc injection would affect corrosion on fuel cladding because the measured thickness of oxide film was included in past database.

  14. Summary Water Chemistry ・Concentration of zinc in primary water was controlled well within the target value (5-7 ppb). ・ Although concentration of the radioactive Co was increased by a factor of 10 with Zn injection than before, the increase was included within the expectation based on the European experience. ・ The increase in Zn-65 was not found due to using depleted zinc. Dose equivalent rate ・ The zinc injection reduced the dose equivalent rate of primary equipment and pipes to 70-80 % than that of previous outage. Fuel Performance ・ It was not considered that zinc injection (eight months) would affect corrosion on fuel cladding by observing the fuel external appearance and thickness of oxide film on the fuel cladding. Zinc injection in Tsuruga-2 will continue to be performed. Influence of long-term zinc injection on the plant and fuel performances will be estimated.

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