IR 05000312/1986024

Insp Rept 50-312/86-24 on 860624-26 & 0710.No Noncompliance Noted.Major Areas Inspected:Chemical & Radiochemical Measurements

ML20203K985
Person / Time
Site:	Rancho Seco
Issue date:	08/07/1986
From:	Hamada G, Yuhas G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
Shared Package
ML20203K983	List: IR 05000312/1986024 ML20203K981
References
50-312-86-24, NUDOCS 8608220297
Download: ML20203K985 (4)

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U. S. NUCLEAR REUJLATORY COMMISSION

REGION V

Report No. 50-312/86-24 Docket No. 50-312 License No. DPR-54 Licensee: Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Facility Name: Rancho Seco Nuclear Cenerating Station Inspection att flerald, California Inspection Conducted: Jur.e 24-26, July 10, 1986 and telephone discussions conducted on July 14 and 17, 1986 Inspector: * ~

WHLU IV S-7~ Vb G. H llamada Radiation Laboratory Specialist Date Signed Approved fly: FD /!7![ G. Yuhan, Chief Da'te ' Signed Facilities Radiological Protection Section Summary:

Onstte inspection of June 24-26, July 10, 1986 (Repert No. 50-312/86-24)

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Arean Inspected: This was a routine, unannounced inspection of activities involving chemical and radiochemical measurements. A total of 30 onsite inspection hourn were expended by one inspector. This inspection involved activitics covered in inspection procedures 70501, 79701 and 8472 Renultn: No items of noncompliance were identified in the areas inspecte I

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e DETAILS Persons Contacted G. Campbell, Plant Chemist B. Carter, Chemistry Technician

• S. Manofsky, Radiation and Chemistry Supervisor

• R. Miller, Chemistry Superintendent

• C Stevenson, Regulatory Compliance

• T. Tucker, Operations Superintendent W. Wilson, Radiation and Chemistry Supervisor

• Denotes personnel present at exit intervie . Discussion While this inspection was structured to mainly review the " sulfate problem" in the primary coolant, a review of other aspects of the chemistry program was also performed. State-of-the-art systems such as the ion chromatograph, atomic absorption spectrometer, computer based multichannel analyzer, etc., are routinely used to perform measurement Additional chemistry personnel have been hired and highly qualified personnel have been assigned to operate the more sophisticated systems like the ion chromatograph. Because of the prolonged outage of the reactor, confirmatory radioactivity measurement checks were postponed to a later date in favor of a procedure whereby the chemistry laboratory would analyze a spikeet sample provided by the NR Currently, except for the primary coolant where only a few of the longer lived fission and activation products are present, activity levels in other media, e.g.,

charcoal cartridge, filters, etc., are too low to provide meaningful tests for these categorie Rancho seco has committed to conform with the secondary chemistry guidelines provided in PWR Secondary Water Chemistry Guidelines, EPRI,

. hine 1984. They are also committed to conform with the reactor vendor's (IMW) primary water chemistry guidelines. Among the requirements listed in the latter document is a limit of 0.1 ppm (or 100 pph) for sulfate in primary coolant for both operating and cold shutdown conditions. Rancho Seco's technical specifications do not address sulfates in the primary coolan Currently, the primary coolant system is in decay heat removal mod Recently, high sulfate ton levels in primary coolant were observed with typical concentrations of about 100-200 parts per billion (ppb) with occasional readings ranging to levels two to three times higher. While it seemed reasonable to suspect the cation exchange resin as the source of this problem (because of the benzene sulfonic acid functional group in strong acid cation resins), the data did not appear to support this conclusion. All of the high sulfate readings were obtained on coolant samples taken upstream from the mixed resin be Samples of coolant taken downstream from the mixed resin bed showed little or no sulfate This not only indicated that the sulfates were being removed by the resin

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bed (anion) as expected, but also that sulfates were not being released by the resin (cation). During this period when the sulfate anomaly was being investigated, San Onofre (Units 2 and 3) was also experiencing sulfate problems in the secondary water polishing systems. Both San Onofre Unit 2 and Unit 3 secondary polishing systems were using a new type of ion exchange resin recently developed by Dow Chemica Initially, the resin was not thought to be the cause of the problem because the on-line ion chromatograph downstream of the resin beds did not indicate sulfate as a contaminant. Subsequently, however, based on known parameters and the fact that no other likely source of sulfates could be identified, it was tentatively concluded that the cation resin was the source, and that the sulfate fraction was initially stripping off as something other than the sulfate anion (SO 4=), perhaps as benzene sulfonic acid, and later on in the cycle becomes further degraded to the sulfat It has since been confirmed by other means that benzene sulfonic acid can be present in the effluent from resin beds containing the "new" resin heads. At first, the Rancho Seco situation did no appear to be related to the San Onofre problem. The high sulfate at Rancho Seco is in the primary coolant system as opposed to the secondary system at San Onofre, and the ion exchange resin at Rancho Seco is essentially the same resin they have been using for many years as opposed to a new resin at San Onofre. On the other hand, attempts at Rancho Seco to identify the source of the sulfate were not yielding positive result For example, it was dif ficult to verify the hypothesis of a bacterial source of sulfates, or that deposited metal sulfides were being released with subsequent oxidation to sulfate. An experiment was conducted to obtain more information. Simulated reactor coolant was added to a small batch of ion exchange resin (mixed resin) and stirred for several days in an open beaker. A control blank containing only the simulated coolant was treated in like fashion. Sulfate analyses were performed with the Ion Chromatograph. The control blank measured approximately 19 ppb sulfate and the solution containing the ion exchange resin (mixed)

indicated essentially no sulfate. The ion exchange resin was next removed from the liquid and the liquid alone was stirred for several days in an open beaker. This solution measured about 600 ppb sulfate. Based on these results it was hypothesized that sulfate was being released by the cation exchange resin but not in a form immediately identifiable as the sulfate anion, perhaps as benzene sulfonic acid. This release of sulfate was made possible by the action of dissolved oxygen on the cation exchange resin beads. During this outage period, the primary coolant system was in contact with ambient air and consequently, the oxygen level in the coolant was at 3-5 parts per million (ppm) with readings reaching as high as 8 ppm. The fraction containing the sulfate was further oxidized, perhaps abetted by the radiation in the core, to the free sulfate anion. As the coolant passed through the mixed bed demineralizer, the sulfate was removed, but a parallel release of a sulfate component from the cation exchange resin also occurred. This phenomenon was not observed during power operation because the oxygen level is suppressed by excess hydrogen in the coolan The above explanation, on the surface, appeared plausible, but more information was needed. Unfortunately, anomalies started to appear in the ion chromatograph data. During this period, a significant change in the operation of ion chromatograph was made. The existing column in the

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system was replaced with a new column which could provide better a

resolution but which also had less capacity. The anomalies appear to be related to this new column but it is unclear why this is occurring.

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Discussions between Rancho Seco and the manufacturer of the ion

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chromatograph are ongoing and various tests are being performe While this development has raised the question of the validity of recent i sulfate results, it was felt that results obtained prior to the column

change, which include those results obtained for the laboratory I

experiment mentioned above, were valid and that there is a reasonable

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basis for further testing the above hypothesis concerning the role of 4 oxygen in the release of sulfates into the coolant syste If these I

findings can be confirmed, there is a potential that this could be a

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generic issu It ic unclear, however, what, if any significance there

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might be in these findings.

! Currently, the laboratory is involved in resolving the analytical problems associated with the ion chromatograph. A second ion chromatograph is being set up not only to assist in this ef fort but also  ;

to provide added analytical capability to further study the sulfate i

problem.

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3. Exit Interview i

Inspection findings were discussed with licensee personnel indicated in j paragraph Management personnel were informed of NRC's intention to i provide spiked radioactive sample for analysis by chemistry and/or its vendor laboratory.

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