IR 05000324/1987001
| ML20212Q667 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 01/21/1987 |
| From: | Kahle J, Ross W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20212Q654 | List: |
| References | |
| 50-324-87-01, 50-324-87-1, 50-325-87-01, 50-325-87-1, IEIN-86-1061, NUDOCS 8702020330 | |
| Download: ML20212Q667 (7) | |
Text
jk'A f fo UNITED STATES ug'o,
NUCLEAR REGULATORY CCMMISSION j,_
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REGION il
...r 101 MARIETTA STREET, N.W., SUITE 2900
ATLANTA, GEORGIA 30323
%,*****f-JAN 211987 Report Nos.: 50-325/87-01 and 50-324/87-01 Licensee: Carolina Power and Light Company P. O. Box 1551
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Raleigh, NC 27602 Docket Nos.: 50-325 and 50-324 License Nos.: DPR-71 and DPR-62 Facility Name:
Brunswick Steam Electric Plant InspectionConducteq:
January 5-8, 1987 b/ kMC
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Inspectors:
W. J. ps5 Date Signed Approved by:
M r/.te /F 7 J. B. fKaple, Chief Ddte Signed Radio logicalEffluentsandChemistrySection Divist6n of Radiation Safety and Safeguards SUMMARY
Scope:
This special unannounced inspection involved an assessment of the licensee's preparation for and performance of hydrogen water chemistry tests.
Results: No violations or deviations were identified, i
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j C702020330 870121 PDR ADOCK 05000324 Q
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REPORT DETAILS 1.
Persons Contacted Licensee Employees
- C. R. Dietz, General Manager
- J. W. Chase, Assistant to the General Manager
- A. G. Cheatham, Manager, Environmental and Radiation Control (E&RC)
- C. E. Robertson, Supervisor, E&RC
- J. Davis, Senior Project Specialist, E&RC
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T. McEwan, Senior Engineer, Engineering W. Nurnberger, Chemistry Foreman, E&RC P. B. Snead, Senior Engineer, E&RC S. Watson, Project Specialist, E&RC Other Organization
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R. Ivars, Innovative Technologies, Inc.
NRC Resident Inspector L. Garner
- Attended exit interview 2.
Exit Interview
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The inspection scope and findings were summarized on January 8,1987, with
those persons indicated in Paragraph 1 above.
The inspector described the areas inspected and discussed in detail the inspection results.
No dissenting comments were received from the licensee.
The licensee did not identify as proprietary any of the material provided to or reviewed by the inspector during this inspection.
3.
Licensee Action on Previous Enforcement Matters This subject was not addressed in the inspection.
4.
Hydrogen Water Chemistry Tests The main p(urpose of this inspection was to monitor the hydrogen water chemistry HWC) tests that were being performed on Brunswick Unit 2.
These tests were designed to determine the degree to which intergranular stress corrosion cracking (IGSCC) of stainless steel could be mitigated by controlling one of the causes of this type of corrosion, dissolved oxygen in the reactor coolant, through the addition of gaseous hydrogen.
Indications of IGSCC had been observed in both units in recent years and had necessitated considerable effort and radiation exposure to be expended for
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repair.
The technology on which the tests were based had been developed subsequent to the discovery that this problem was widespread among BWRs.
The purposes of the HWC tests were as follows:
To determine if the concentration of oxygen dissolved in the reactor coolant could be reduced sufficiently to decrease the electrochemical potential of stainless steel to - 0.230 volts.
To determine if IGSCC of stainless steel is mitigated at this protective electropotential.
To determine if a tolerable background radiation level could be maintained under conditions that mitigated IGSCC.
To determine if excess hydrogen gas could be disposed of safely through the plant's air-ejector system.
a.
Pre-test Activities
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Through discussions with plant personnel and review of pertinent documents the inspector reviewed the actions taken by the licensee prior to the start of the HWC tests.
(1) Procedure SP-86-081 had been developed to cover all aspects of the HWC tests.
As part of this procedure, the licensee had performed a safety evaluation of the technology involved and the control of
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large volumes of hydrogen and oxygen gases during the tests.
On the basis of this safety evaluation, the licensee concluded that the HWC tests did not involve an unreviewed safety issue, and the special procedures were consistent with industry codes (e.g.,
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National Fire Protection Association) and NRC guidance (e.g., BTP CMEB 9.5-1 Guidelines for Fire Protection for Nuclear Power Plants).
(2) Permission had been obtained from the NRC to temporarily increase the radiation set points on the main steam monitors (by a factor
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of five) to prevent these set points from being exceeded by
increased radiation levels in the steam during the HWC tests.
l Previous development work at other sites had shown that injections of hydrogen into the reactor coolant increased the amount of nitrogen-16 (gamma ray energies of 5 and 6 mev) in the steam.
(3) Procedure SP-86-096 had been developed for use by the Environmental and Radiation Control Group (E&RC) to provide chemistry and health physics support during the tests.
In expectation of increased background radiation levels an augmented radiation monitoring program had been developed.
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(4) Specialists in HWC had been contracted to perform the injection of hydrogen and to perform the electrochemical and metallurgical experiments with specimen of stainless steel.
b.
Summary of HWC Tests Beginning January 3,1987, hydrogen was continually injected into the feedwater of Unit 2 through the suction of the condensate booster pumps.
The initial plan had been to increase the hydrogen injection flow rate from zero to 70 standard cubic feet per minute (SCFM) over a period of several days while the electrochemical and radiation level measurements were being taken.
However, the flow rate increase was terminated at 34 SCFM after six increments (7,10,15, 21, 27 and 34 SCFM) because the optimum reduction of oxygen (and the protective point on the electrochemical scale) had been established at 10 SCFM.
Subsequently, the injection rate was maintained at 10 SCFM while the crack mitigating tests were performed. Unfortunately, on the third day of the test the unit scrammed because of a problem unrelated to the HWC tests.
After reviewing the data that had been obtained, the licensee decided that the results of the tests were sufficient and the tests should be terminated.
Throughout the test the radiation background had been monitored at 119 points throughout the plant site, with the greatest concentration of monitors being inside the Turbine Building and nearby unshielded and inhabited areas of the plant.
At no time did the radiation level become hazardous or jeopardize the continuation of the tests.
As the injection flow rate of hydrogen was increased the licensee monitored the air ejector and gaseous effluent systems and added oxygen upstream of the hydrogen-oxygen recombiners to ensure that excess oxygen was present to react with the hydrogen that was carried over in the steam.
c.
Summary of Test Results (1) Reduction of Oxygen in the Reactor Coolant While Unit was operating at greater than 90% power the hydrogen injection rate was increased until a maximum concentration of approximately 1200 ppb of H was attained in the feedwater. Under these conditions the conce)tration of oxygen dissolved in the reactor water decreased from approximately 150 ppb to less than detectable.
A flow rate of 10 SCFM was chosen for subsequent tests because~ at this flow rate there was a detectable (approximately 10 ppb) concentration of residual oxygen in the reactor water as required by the HWC theory of corrosion preventio.
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(2) Radiation Level As the hydrogen injection rate was increased to 34 SCFM the background radiation level increased by a -factor of four.
The plant process and radiation monitors tracked closely with the additional monitors that were installed for the HWC tests.
The maximum background level did not become excessive; e.g., at the radiation control point near the plant entrance the background increased from 60 cpm to 160 cpm.
The greatest increase in radiation level at the Control Building was approximately 1.5 mr/hr.
When the injection rate was maintained at 10 SCFM of hydrogen, there were no significant increases in radiation level at any critical location.
As expected, the injection of hydrogen also shifted the radiolytic reactions to produce more ammonia (NH3) and less oxides. of nitrogen.
Therefore, the radiation level of nitrogen-16 in lines that carried reactor water decreased, thereby reducing the background levels slightly in the vicinity of these water lines.
(3) Electrochemical Measurements During the variation of hydrogen injection flow rate the electrochemical potentials of multiple specimen of types 304 and 316 stainless steel were being measured versus a silver-silver chloride electrode. This electrochemical potential difference was converted mathematically to the potential versus a standard hydrogen electrode.
As predicted, the potentials decreased (became more negative) directly with oxygen concentrations regardless of the presence or absence of an oxide film on the SHE were obtained with the higher injection rates (y -0.6 volt vs metal.
Although potentials as low as approximatel when the oxygen concentration was immeasurably low) the licensee selected a potential of - 0.230 volts as being sufficiently low to mitigate IGSCC.
(4) Crack Growth /Redandation Studies The effect of HWC under optimum conditions (10 SCFM injection rate) on the propagation of cracks in 304SS was established with three pre-cracked specimens that were maintained under constant strain of 30, 35 and 40 megapascals.
The cracked specimen had been " soaked" in an autoclave loop at 500'F under normal reactor coolant conditions for 45 days prior to the HWC tests.
During this 45-day period the specimen under greatest strain had exhibited a crack growth of 2 mm.
Af ter HWC was begun no additional crack growth was observed in any specimen.
Although the HWC test lasted only three days the licensee considered the apparent mitigation effect to be vali..
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(5) Effect of HWC on Reactor Materials i
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During the HWC tests not only were hydrogen and oxygen measured
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i continually in the feedwater and reactor water to control the i
i experiments but the licensee also monitored the reactor water for
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i impurities (chloride, nitrate, sulfate, specific conductivity) and
i evidence of corrosion / erosion (e.g.,
chromium-51, insoluble copper, and insoluble iron).
At the initiation of the HWC tests the purity of the reactor water was very high; i.e., conductivity of approximately 0.15 umho/cm; nitrate, sulfate, and chloride less
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than 5 ppb; insoluble copper and iron less than 2 ppb and 10 ppb
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respectively.
Although most of the trace ions exhibited no l
significant changes when hydrogen was added, the conductivity l
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dropped sharply to approximately 0.08 umho/cm when the injection
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rate was equal to 10 SCFM. The licensee attributed this effect to
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the reduction of and precipitation of chromium.
No evidence of l
increased corrosion was rioted. A similar decrease in nitrate ions j
may have been caused by the reduction of these ions to ammonia, i
)i (6) Sumary
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Although the licensee's test was terminated earlier than planned
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the results were considered to be positive in that propagation of IGSCC was terminated and low oxygen was maintained with a
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relatively low injection rate (10 SCFM) of hydrogen.
At this
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injection rate there was no evidence of any detrimental effect on
the reactor system nor was there a significant increase in j
background radiation level, j
No violations or deviations were identified.
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5.
Water Chemistry Control Program (79701)
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j Through discussions with chemistry personnel and a review of chemistry i
procedures and graphical records the inspector made a partial reassessment j
of the licensee's progress in controlling water chemistry, i
The quality of the water coolant as reflected by the specific
conductivity was being maintained within limits consistent with HWC
j criteria and BWROG guidelines.
l Since the inspector's last site visit the licensee had promulgated
i corporate and plant policies that endorsed the BWROG guidelines.
An
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Administrative Instruction. Al-81, provided guidance to all plant
j personnel and departments for implementing these policies.
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Problems with leakage of powdered resins from the RWCU demineralizers
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had been encountered.
The licensee was looking at other types of
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j filter /demineralizer resin holders in an effort to improve the
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j integrity of the holders.
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The inspector was informed that increased attention was being given to all aspects of chemistry training, i
No violations or deviations were identified.
6.
IE Information Notice No.86-106, Feedwater Line Break During this site visit the inspector and various members of the licensee's staff discussed the incident covered in this Notice and the applicability of the Notice to the Brunswick Units.
In addition, the subjects of generalized corrosion and its control through the implementation of BWROG guidelines were discussed. The inspector found the licensee to be knowledgeable of the feedwater line break discussed in the Notice.
Also, personnel had been assigned the responsibility for developing the licensee's course of action in relation to the Notice.
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