The Three Mile Island Accident - American Chemical Society

6 Water Chemistry 1

2

Κ. J. Hofstetter and V. F. Baston 1

GPU Nuclear Corporation, Middletown, PA 17057 Physical Sciences Inc., Sun Valley, ID 83353

Downloaded by GEORGETOWN UNIV on February 5, 2017 | http://pubs.acs.org Publication Date: December 23, 1986 | doi: 10.1021/bk-1986-0293.ch006

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Prior to the accident, the coolants in the primary and secondary systems were within normal chemistry specifi cations for an operating pressurized water reactor with once-through steam generators. During and immediately after the accident, additional boric acid and sodium hydroxide were added to the primary coolant for control of criticality and radioiodine solubility. A primary to secondary leak developed contaminating the water in one steam generator. For about 5 years after the accident, the primary coolant was maintained at 3800 ± 100 ppm boron and 1000 ± 100 ppm sodium concentrations. Dis solved oxygen was maintained 7.5, corrosion caused by increased dissolved oxygen levels (up to 8 ppm) and higher chloride ion content (up to 5 ppm) is minimized. Chemical control of dissolved oxygen was discontinued and the coolant was processed. Prior to removal of the reactor vessel head, the boron concentration in the coolant was increased to ≡ 5000 ppm to support future defueling operations. Decontamination of the accident generated water is described in terms of contaminated water management. In addition, the decontamination and chemical lay-up conditions for the secondary system are presented along with an overview of chemical management at TMI-2. The accident at Three Mile Island Unit-2 (TMI-2) resulted in the release of large quantities of fission products to various reactor systems and components. These fission products contaminated liquids in many tanks which in turn produced flooding in the reactor containment building and associated auxiliary buildings. As a result, water decontamination ( i . e . , the removal of radionuclides) has been a major effort in the recovery of TMI-2 (1-5). Because of the large quantity of "accident generated" water which s t i l l contains tritium 0097-6156/86/0293-0108$06.00/0 © 1986 American Chemical Society

Toth et al.; The Three Mile Island Accident ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

6.

HOFSTETTER AND Β ASTON

Water Chemistry

109


( p r e s e n t i n v e n t o r y 1,9 m i l l i o n g a l l o n s ) , t h e l i m i t e d p o s t - a c c i d e n t water storage c a p a c i t y (2,2 m i l l i o n g a l l o n s ) , and e x i s t i n g r e g u l a t o r y a g r e e m e n t s p e r m i t t i n g n o d i s c h a r g e , s o u n d management o f c o n t a m inated water required t h ere-use o f previously decontaminated water. I n many c a s e s , c h e m i c a l a d d i t i o n s w e r e r e q u i r e d t o t h e p o s t - d e c o n tamination water p r i o r t o i t s use i n various systems. This paper d i s c u s s e s t h e c h e m i c a l p r o p e r t i e s o f w a t e r s b o t h p r e - and p o s t - d e contamination, t h e chemical adjustments required p r i o r t o re-use and the status o f systems. I t a l s o d i s c u s s e s t h e e v a l u a t i o n methods f o r the use o f chemicals i n t h edecontamination andd e f u e l i n g a c t i v i ties. History The r e a c t o r c o o l a n t r e c e i v e d t h e b u l k o f t h e f i s s i o n p r o d u c t s released from the f u e l . In t u r n , leaking coolant contaminated other systems. A l lp o r t i o n s o f t h ecoolant p u r i f i c a t i o n system accumulat ed h i g h c o n c e n t r a t i o n s o f f i s s i o n p r o d u c t s . A coolant leak contam i n a t e d t h e secondary ( n o r m a l l y c l e a n ) s i d e o f one steam g e n e r a t o r . Leakage o f c o o l a n t from t h e r e a c t o r system r e s u l t e d i n = 650,000 g a l l o n s o f h i g h l y c o n t a m i n a t e d w a t e r c o l l e c t i n g i n t h ebasement o f the r e a c t o r b u i l d i n g . T r a n s f e r s from t h e r e a c t o r b u i l d i n g basement a l s o contaminated large areas o f a u x i l i a r y b u i l d i n g s , as tanks and sumps o v e r f l o w e d . One m o n t h a f t e r t h e a c c i d e n t , t h e r e e x i s t e d = 1 m i l l i o n g a l l o n s o f contaminated water c o n t a i n i n g about o n e - h a l f o f the core inventory o f Cs (=360,000 C i ) . W h i l e numerous s o l u t i o n s w i t h w i d e l y d i f f e r i n g c h e m i c a l c o m p o s i t i o n s were encountered d u r i n g t h e d e c o n t a m i n a t i o n o f t h i s a c c i d e n t g e n e r a t e d w a t e r , some c o m m o n a l i t y w a s e v i d e n t ; n a m e l y , t h e m a j o r s o l u t e s were b o r i c a c i d and sodium h y d r o x i d e i n v a r y i n g p r o p o r t i o n s . The b u l k p r o p e r t i e s o f t h e s o l u t i o n s w e r e d e t e r m i n e d a n d c o r r e l a t e d by a few s i m p l e a n a l y s e s , i . e . , p H , c o n d u c t i v i t y , b o r o n and sodium concentrations. These c h e m i c a l a n a l y s e s were p e r f o r m e d , as a minimum, on a l l i n f l u e n t and e f f l u e n t samples t a k e n d u r i n g l i q u i d decontamination. Specialized analyses f o r i o n i c species present i n t r a c e amounts ( e . g . , c h l o r i d e , s u l f a t e , e t c . ) were a l s o p e r f o r m e d o n s e l e c t e d samples. R a d i o n u c l i d e d e t e r m i n a t i o n s w e r e made b y a v a r i e t y o f r a d i o c h e m i c a l methods i n c l u d i n g gamma-ray s p e c t r o s c o p y , radiochemical separations, l i q u i d s c i n t i l l a t i o n spectrometry and proportional counting. These a n a l y s e s and t h e l a b o r a t o r y f a c i l i t i e s a t TMI-2 r e q u i r e d t o support d e c o n t a m i n a t i o n a c t i v i t i e s a r e d i s c u s s e d i n r e f e r e n c e 1. The f o l l o w i n g d i s c u s s i o n i s o r g a n i z e d i n c h r o n o l o g i c a l o r d e r o f major l i q u i d cleanup operations. Decontamination o f general areas i s i n c l u d e d i n t h e d i s c u s s i o n o f each a r e a . Chemical adjustments required f o r d e f u e l i n g a r e presented as they apply t o t h e i n d i v i d u a l systems. Auxiliary

andFuel Handling

Buildings

As a r e s u l t o f a c t i o n s t a k e n t o r e c o v e r f r o m t h e l o s s - o f - c o o l a n t a c c i d e n t , t h e R e a c t o r C o o l a n t B l e e d h o l d u p T a n k s (RCBT) w e r e n e a r l y f i l l e d w i t h contaminated coolant. Other tanks i n t h e a u x i l i a r y


THE THREE MILE ISLAND ACCIDENT

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b u i l d i n g s were a l s o near c a p a c i t y . I n order t o reduce t h e contam inated water inventory and a l s o gain access t o lower e l e v a t i o n s i n the a u x i l i a r y b u i l d i n g s , a c o m m e r c i a l vendor (EPICOR, I n c . ) was contracted s h o r t l y a f t e r t h e accident t o decontaminate t h i s water. A w a t e r d e c o n t a m i n a t i o n system was q u i c k l y i n s t a l l e d i n an e x i s t i n g b u i l d i n g and c o n s i s t e d o f t h r e e i o n exchange p r o c e s s i n g vessels, operated i n s e r i e s , i n t e r p o s e d between two s t a g i n g tanks. Using the v e n d o r ' s p r o p r i e t a r y r e s i n m i x e s , a p p r o x i m a t e l y 550,000 g a l l o n s o f w a t e r f r o m v a r i o u s t a n k s a n d sumps i n t h e a u x i l i a r y b u i l d i n g s w e r e " p r o c e s s e d " d u r i n g t h e p e r i o d f r o m November 1979 t o A u g u s t 1 9 8 0 . A summary o f t h e c h e m i c a l c o m p o s i t i o n o f t h e w a t e r p r o c e s s e d a n d t h e concentrations o f t h emajor l o n g - l i v e d r a d i o n u c l i d e s i s given i n T a b l e I. M o s t c a t i o n s a n d some a n i o n s w e r e r e m o v e d f r o m t h e l i q u i d s during decontamination. The c h e m i c a l and r a d i o c h e m i c a l p r o p e r t i e s of t h e e f f l u e n t s o l u t i o n s a r e a l s o summarized i n T a b l e 1 and i l l u s trate thehigh decontamination factor achieved f o r the demineralization process.

T A B L E I.

A Summary o f C h e m i c a l P r o p e r t i e s o f W a t e r i n A u x i l i a r y B u i l d i n g s P r e - and P o s t - Decontamination Using EPICOR,Inc. Resins

Analysis

Before

After

pH Β (ppm) Na (ppm) C I (ppm) S0 (ppm)

8 1000 300 15 150

6 860 20

4

Ifcs (yCi/mL) Sr

(yCi/mL)

17 1

200 >10% >1000 15000 1620 3550 11.2 490

Demineralizer Resin

>200 >10% >1000 10000 2420 4600 4.57

-

Controls on Use of Chemicals Because the decontamination of systems and areas i s e s s e n t i a l l y a chemical problem, a procedural review and approval system was devel oped to control the use of chemicals at TMI-2. Prior to use, each chemical must be formally evaluated against multiple c r i t e r i a . A methodology was developed to evaluate the safety of chemicals with the goal of preventing harm to personnel, property and the environ ment during chemical transport, use, storage and disposal. Chemi cals are evaluated with emphasis on i n d u s t r i a l safety, material and chemical compatibility, corrosion, r e a c t i v i t y , radioactive and hazardous waste management, and c r i t i c a l i t y . "Chemical coders" review the proposed use of chemicals and designate hazard types and levels from chemical evaluations, vendor data, OSHA Material Safety Data Sheets and other references. These chemical evaluations become part of any work instructions where chemicals are to be used. Any special l i m i t s and precautions are annotated. Approval to use the chemicals i s made only after a comprehensive examination of benefits and r i s k s .


THE THREE MILE ISLAND ACCIDENT

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Examples of chemicals that have been approved for use at TMI-2 i n clude: concentrated 3 ^ FREON for the electropolishing decon tamination of small tools and components ( l i q u i d waste i s s o l i d i f i e d p r i o r to disposal); TRITON X-100, a surfactant used i n l o c a l i z e d decontamination (limited to 0.1% solution for disposal i n l i q u i d radwaste system); sulfamic acid for the decontamination of concrete surfaces (localized use with s o l i d i f i c a t i o n of l i q u i d waste); e t c . Future large scale decontamination chemical use w i l l be evaluated by these same c r i t e r i a . H

P 0

a

n

d


Summary The chemical conditions of water used to support defueling and decontamination of TMI-2 w i l l continue to be monitored and changed as required. Presently, boric acid and sodium hydroxide are being added to =350,000 gallons of previously decontaminated water i n order to f i l l the f u e l transfer canal and f u e l storage pool i n support of defueling.

The management of contaminated water i s a high p r i o r i t y e f f o r t i n the recovery of TMI-2. To date, nearly 3.3 m i l l i o n gallons of water have been processed through SDS and EPICOR I I . Of the present 1.9 m i l l i o n gallons of accident generated water inventory, approximately 80% has been processed i n a once-through mode. The remaining water i s continually being re-used and re-processed to support decontam ination and defueling a c t i v i t i e s resulting i n a considerable cost savings and minimizing the increase of contaminated water inventory. Planning i s underway to explore chemical reagents for internal systems decontamination. The use of chemicals w i l l be t i g h t l y controlled to prevent injury to personnel and to prevent damage to systems. Analysis methods for chemical species w i l l be developed to support these operations as defueling and decontamination operations require.

Literature Cited 1. K. J. Hofstetter, C. G. Hitz, K. L. Harner, P. S. Stoner, G. Chevalier, H. E. Collins, P. Grahn and W. F. Pitka, "Chemistry Support For Submerged Demineralizer System Operation at Three Mile Island", Analytical Chemistry in Energy Technology, ed. by W. S. Lyon, Ann Arbor Science, p. 301 ff, (1982). 2. K. J. Hofstetter, C. G. Hitz, T. D. Lookabill and S. J. Eichfeld, "Submerged Demineralizer System Design, Operation and Results", Proceedings of ANS-CNA Joint Topical Meeting on Decontamination of Nuclear Facilities, Niagra Falls, Vol. 2, p 5-81 (1982). 3. Κ. J. Hofstetter and C. G. Hitz, "Processing of the TMI-2 Reactor Building Sump and Reactor Coolant System", Proceedings of 1982 ANS Winter Meeting, Washington, DC, Vol. 43, p 146 (1982).


6. HOFSTETTER AND BASTON

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4. K. J. Hofstetter and C. G. Hitz, "The Use of the Submerged Demineralizer System at Three Mile Island", Separation Science and Technology, 18 (14 & 15), p 1747-1764 (1983). 5. H. F. Sanchez and G. J. Quinn, "Submerged Demineralizer System Processing of TMI-2 Accident Waste Water", US Department of Energy Report GEND-031 (February 1983).


6. C. V. McIsaac and D. G. Keefer, "TMI-2 Reactor Building Source Term Measurements: Surface and Basement Water and Sediment", US Department of Energy Report GEND-042 (October 1984). 7. D. O. Campbell, E. D. Collins, L. J. King and J. B. Knauer, "Evaluation of the Submerged Demineralizer System (SDS) Flowsheet for Decontamination of High-Activity-Level Water at the Three Mile Island Unit Nuclear Power Station", Oak Ridge National Laboratory Report ORNL/TM-7448 (July 1980). 8. "Reactor Building Radiological Characterization" Vol. I and II, TMI-2 Technical Planning Department/GPU Nuclear Internal Report TPO/TMI-125 (Unpublished). 9. K. J. Hofstetter, C. G. Hitz, V. F. Baston, A. P. Malinauskas, "Radionuclide Analysis Taken During Primary Coolant Decontamination at Three Mile Island Indicate General Circulation", Nuclear Technology, Vol. 63, No. 3 (December 1983). 10. V. F. Baston and K. J. Hofstetter, "Long Term Appearance Rate of Radionuclides in TMI-2 Coolant", Proceedings of 1984 ANS Winter Meeting, Washington, DC, Vol. 47, p 111 (1984). 11. R. E. Mesmer, C. F. Bates, Jr., and F. H. Sweeton "Acidity Measurements at Elevated Temperatures. VI. Boric Acid Equilibria", Inorganic Chemistry Vol. II, No. 3, p 537 ff (1972). 12. "Solubility Isotherms in the System Borax-Boric Acid-Water at 0-94 °C", data provided by US Borax (private communication). 13. M. K. Mahaffey, E. J. Renkey, W. W. Jenkins, L. M. Martinson and R. D. Hensyel, "Resin and Debris Removal System Conceptual Design - Three Mile Island Nuclear Station Unit 2 Makeup and Purification Demineralizer", Hanford Engineering Development Laboratory Report HEDL-7335 (March 1983). RECEIVED June 27, 1985


The Three Mile Island Accident - American Chemical Society

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