ML18283B523

Response to Inspection Conducted on 07/18-19/1977 & Reported in Inspection Report Nos. 05000259/1977012, 05000260/1977012, & 05000296/1977012

ML18283B523
Person / Time
Site:	Browns Ferry
Issue date:	08/22/1977
From:	Gilleland J Tennessee Valley Authority
To:	O'Reilly J NRC/RGN-II
References
IR 1977012
Download: ML18283B523 (14)

Text

830 Power Building TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 37401 August 22, 1977 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U;S. Nuclear Regulatory Commission Region II Suite 1217 230 Peachtree Street, NW.

Atlanta, Georgia 30303

Dear Mr. O'Reilly:

This is in response to J. T. Sutherland's August 2, 1977, letter, RII:WEC 50-259/77-12, 50-260/77-12, 50-296/77-12, which transmitted for our review an IE Inspection Report (same number). We have reviewed that report and do not consider any part of proprietary.

it to be

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Very ru y yo rs E. Gilleland Assistant Manager o

/i'J.

Power An Equaf Opportunity Employer

~P,R REGIj~ UNITED STATES NUCLEAR REGULATORY COMMISSION REGION II 230 PEACHTREE STREET, N.W. SUITE 1217 ATLANTA,GEORGIA 30303 AUG 2 1977

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In Reply Refer To:

RII:WEC 50-259/77-12 50-260/77-12 50-296/77-12 Tennessee Valley Authority Attn: Mr. Godwin Williams, Jr.

Manager of Power 830 Power Building Chattanooga, Tennessee 37401=

Gentlemen:

This refers to the inspection conducted by Mr. W. E. Cline of this office on July 18-19, 1977, of activities authorized by NRC Operating License Nos. DPR-33, DPR-52 and DPR-68 for the Browns Ferry 'Nuclear Plant facilities, and to the discussion of our findings held with 0 Mr. H. L. Abercrombie at the conclusion of the inspection.

Areas examined during the inspection and our findings are discussed in the attached inspection report. Within these areas, the inspection consisted of selective examinations of procedures and representative records, interviews with personnel, and observations by the inspector.

Within the scope, of this inspection, no items of noncompliance were disclosed.

We have examined actions you have taken with regard to previously identified inspection findings. These are discussed in the attached inspection report.

In accordance with Section 2.790 of the NRC's "Rules of Practice,"

Part 2, Title 10, Code of Federal Regulations, a copy of this letter and the attached inspection report will be placed in the NRC's Public Document Room. If this report contains any information that you believe to be proprietary, it is necessary that you submit a written application to this office requesting that such information be withheld from public disclosure. If no proprietary information is identified, a written statement to that effect should be submitted. If an application is submitted, it must fully identify the bases for which information is claimed to be proprietary. The application should be prepared so that

4 Tennessee Valley Authority information sought to be withheld is incorporated in a separate paper and referenced in the application since the application will be placed in the Public Document Room. Your application, or written statement, should be submitted to us within 20 days. If we are not contacted as specified, the attached report and this letter may then be placed in the Public Document Room.

Should you have any questions concerning this letter, we will be glad to discuss them with you.

W Very truly yours, Fuel Facility and Materials Safety Branch

Attachment:

RII Inspection Report Nos.

50-259/77-12, 50-270/77-12 and 50-296/77-12 cc: Mr. J. G. Dewease Plant Superintendent Box 2000 Decatur, Alabama 35602

1P,Q RE0( UNITED STATES g

NUCLEAR REGULATORY COMMISSION REGION II 230 PEACHTREE STREET, N.W. SUITE 1217 ATLANTA,GEORGIA 30303

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Report Nos.: 50-259/77-12, 50-260/77-12 and 50-296/77-12 Docket Nos.: 50-259, 50-260 and 50-296 License Nos.: DPR-33, DPR-52 and DPR-68 Licensee: Tennessee Valley Authority 830 Power Building Chattanooga, Tennessee 37401 Facility Name: Browns Ferry Nuclear Plant Units 1, 2 and 3 Inspection at: Browns Ferry Site, Limestone County, Alabama Inspection conducted: July 18-19, 1977 Inspector: W. E. Cl ne Reviewed by:

A. F. Gibson, Chief Date Radiation Support Section Fuel Facility and Materials Safety Branch Ins ection Summar Ins ection on Jul 18-19 1977 {Re ort Nos. 50-259/77-12 50-260/77-12 50-296/77-12)

Areas Ins ected: Special, unannounced inspection following a report by the licensee of heating problems in the offgas system. Inspection included review of gaseous effluent records and calculations, examination of carbon adsorber vessels, review of selected monitor strip charts, and discussions with licensee representatives. The inspection involved approximately six inspectors-hours on site by one NRC inspector.

Results: Of the areas inspected, no items of noncompliance or deviations were identified.

RII Rpt. Nos. 50-259/77-12, 50-260/77-12 and 50-296/77-12 I-1 DETAILS I Prepared by:

W. E. Cline, Radiation Specialist rz Date Radiation Support Section Fuel Facility and Materials Safety Branch Dates of Inspection: July 18-19, 1977 Reviewed by:

A. F. Gibson, Chief Date Radiation Support Section Fuel Facility and Materials Safety Branch

1. Persons Contacted J. G. Dewease, Plant Superintendent

• H. L. Abercrombie, Assistant Plant Superintendent

• W. Thomison, Chemical Engineer

• G. Brantley, Chemical Engineer

• T. P. Bragg, QA Supervisor The inspector also interviewed three operations personnel.

• Denotes those present at the exit interview.

2. Descri tion of Incident At approximately 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on July 17, 1977, the licensee observed temperature increases in five carbon adsorber vessels of the unit 3 offgas system. Within an hour of this time, temperature indication for the 3B adsorber vessel was offscale on the temperature chart recorder (>150 0 F). Four of the other vessels0 gave indication of temperature increase but were less than 150 F. According to licensee representatives, once the problem was recognized action was taken to bypass the system and an investigation was initiated.

At the time of the inspection the cause of the heating in the adsorber vessels was unknown; however, licensee representatives indicated that priority was being placed on determining the cause.

A review of strip chart records for the period July 16-17, 1977 for the offgas system provided some information as to the sequence of events prior to the heating incident in the adsorber. The strip charts showed lower than normal recombiner temperatures prior to 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on July 17, 1977, but after '1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> an increase in temperature was observed. Offgas reheater inlet temperature and adsorber vault temperature increased around 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />. The strip charts also showed erratic variation in the inlet flow to the

RII Rpt. Nos. 50-259/77-12, 50-260/77-12 and 50-296/77-12 I-2 offgas holdup line between the 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> and 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />. A the strip chart results for the H analyzer showed no increase in review'f H concentration prior to the heating incident. According to licensee representatives, several offgas grab samples were taken on the morning of July 17, 1977. One of the grab samples did provide an indication of the presence of H , but the exact quantity could not be determined. In view of the aforementioned information, the inspector questioned licensee representatives about possible causes of the heating incident. Licensee representatives reiterated that the incident was still under investigation and, that with the limited data on hand at the time, the cause could not be determined.

A licensee representative stated however that the heating occurred shortly after problems were encountered with the steam jet air egectors in trying to maintain the proper amount of dilution flow.

Licensee corrective actions, results of offgas release record reviews, and licensee reporting of the incident is discussed below.

3~ Licensee Corrective Actions Licensee representatives informed the inspector that shortly after (at approximately 8 p.m.) the heating problem was discovered the system was isolated and bypassed. The inspector was further informed that entry into the adsorber vault was made (under increased health physics surveillance) in order to inspect the vessels. A nitrogen purge was placed on the vessels as an aid in controlling the heating and to extinguish fire if present. One July 18, 1977, the inspector in the presence of a licensee representative entered the adsorber vault and inspected the adsorber vessels. The inspector observed discoloration of the upper portion of the 3B vessel and the lower portion of the 3D vessel. The inspector also noted that the upper portion of vessel 3B and the lower portion of vessel 3D were still warm. A review of temperature records for the vessels showed that vessel 3B was at 340 0 F and the other vessels were less than 150 0 F.

All vessels appeared to have maintained their integrity during the incident.

4, Off as Release Records The inspector reviewed records of effluent releases via the offgas system and the plant stack for the period July 16, 1977 to July 18, 1977.

Based on the record review, the inspector concluded that no release limits had been exceeded during the incident in that release values for gases, particulates and iodine were below technical specification limit's. The release valves observed did not appear abnormal as compared to other routine releases at the same power level.

ca RII Rpt. Nos. 50-259/77-12, 50-260/77-12 and 50-296/77-12 I-3 5~ Environmental Sam le Results The inspector questioned licensee representatives concerning the results of environmental air samples taken about the plant during the time frame of the incident. Licensee representatives indicated that weekly air samples were taken and that the results for the period of interest could be obtained from the TVA radiological environmental group at Muscle Shoals, Alabama by July 22, 1977.

The inspector telephoned a representative of the TVA radiological environmental group on July 26, 1977 and requested information concerning the environmental air sample results for the period in which the incident occurred. The TVA representative indicated that no significant increases in iodine or particulates were noted from the environmental sampling network. The inspector indicated that the environmental sample results would be reviewed on a subsequent inspection.

6. Licensee Re orts The inspector questioned licensee representatives during the management interview about submitting a formal report of the incident to the NRC. Licensee representatives agreed to submit such a report and to keep the NRC apprised of investigation findings and action taken with regard to the incident.

7 ~ Tests and Evaluations The inspector questioned licensee management representatives as to whether: (1) DOP tests would be performed on the HEPA filters downstream of the carbon adsorbers, and (2) tests would be performed on the carbon adsorber media. The licensee management representative indicated that the necessary tests and evaluation of equipment would be performed so as to determine whether the equipment met the original design and operational criteria. He further indicated that actions (to include repair or replacement of components) would be taken to assure the original design and operational criteria were met. The inspector also questioned: (1) Why adsorber vessel 3E did not have a temperature indication, and (2) Why only single temperature indicators were used on four of the vessels, especially in view of the localized heating phenomenon observed in the 3B and 3D adsorber vessels. The licensee management representative was unable to answer the question, but indicated that this matter would be discussed with the TVA Division of Engineering Design. All of the above matters remain open.

Browns Ferr Off as Adsorber Problem vessels in the Unit 3 offgas system experienced heat buildup. The charcoal adsorber vessels are about 30" in diameter and about 20'-

25'igh. On the day of the incident the offgas system was aligned so that gas passed through two parallel trains; each train contained three vessels arranged in series. The system can be aligned to have series flow through all six adsorbers. The exact cause of the heating within the vessels is not known at this time and is still being investigated by the licensee. However, problems associated with the Steam Jet Air Ejectors, lead some licensee representatives to ~seculate that more steam was released to the offgas system than the system had capacity to handle and thus moisture was introduced densely packed charcoal then heated spontaneously. It should be noted that Sax Chemical Handbook indicates that spontaneous heating can occur in charcoal if it is tightly packed and moist.

also be noted that licensee has experienced problems with the It should Unit 3 offgas recombiner and a "grab" sample revealed the presence of hydrogen in the offgas system downstream of the recombiner on the morning of July 17, 1977. A review of the strip chart for the hydrogen analyzer during this same period showed no indication of hydrogen. In a telephone conversation with a licensee representative on July 28, 1977, the representative said that the HEPA filters upstream and downstream of the adsorbers had been replaced and that deformation of these filters had been observed. Such deformation

~ml ht have been due to overpressurization as opposed to heating.

2 ~ How discovered? Answer: Shortly after 1330 hour0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> CDT on July 17, 1977, licensee representatives observed increases in temperature indication on the Unit 3 offgas adsorber vessels chart recorder.

The chart recording for the 3B adsorber (the second adsorber in the first train) went off the chart recorder scale (>150 F). The exact temperature of the 3B vessel was unknown, but a licensee repre-sentative stated that a measurement of current from the thermo-0 couple indicated that the temperature was on the order of 1000 F.

The heating problem was also indicated by the Unit 3 vault tempera-ture monitor which began to show an increase around 1300 to 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> CDT.

3~ Worst Conditions Possible? Answer: The worst possible condition would apparently be a breach of charcoal vessel integrity with the resultant release of heated charcoal to the vault and release of the entire inventory of noble gases and iodine from the charcoal to the atmosphere via the main stack. The licensee has address the breaching of the adsorber beds at ambient temperature conditions in

section 9.5 of the FSAR. In the analysis the licensee makes the assumption that the bed has been in operation for 10 years and that all of the iodine is on the first bed. The licensee further assumes that the failure of the first bed would result in release of 1% of the iodine from the bed, and that failure of all six beds would only result in a release of 10% of the noble gases. Based on these failures and release rates the licensee estimates resultant exposures at 1400 meters from the plant as 5.6 mrem due to iodine and 0.6 mrem due to noble gases. Using the licensees inventory values, release rates and meteorological conditions, and ~assumin that heated activated carbon would release 100% of the radionuclides, the resultant exposures at 1400 meters would be about 560 mrem due to iodines and about 6 mrem due to noble gases. The "possibility" that the latter levels could be attained is somewhat doubtful in view of the fact Unit 3 is a relatively new operational unit (initial criticality August 8, 1976) with a resultant low radio-nuclide inventory. This low inventory was further evidenced by the low radiation levels (approximately 1 to 2 mrem/hr) at the adsorber vessels and within the vault.

What found when o ened u  ? Answer: The licensee entered the adsorber vault, under increased health physics surveillance, on July 18, 1977. According to licensee representatives radiation levels in the adsorber vault were on the order of 1 to 2 mrem/hr thus indicating relatively low levels of radioactivity in the charcoal beds. On the afternoon of July 18, 1977, an inspector observed from the area radiation monitor in the vault that the radiation level was on the order of 1 to 2 mrem/hr. Licensee representatives indicated that upon inspection of the vessels they noted evidence of vessel heating due to discoloration on at least two of the vessels. However, the integrity of all the vessels was entact. The inspector also examined the adsorber vessels. Vessel 3B (the second vessel in the first train) showed indication of heating (based on discoloration of the vessel) on the upper half of the vessel. Vessel 3D (the first vessel of the second train) showed signs of heating (vessel discoloration) on the lower fifth of the vessel. The inspector noted that those portions of the outside vessels were still warm to the touch on the afternoon of July 18, 1977. Temperature instrumentation, which was being used to provide a periodic meter reading of the vessel mid-line temgerature, showed readings of about 130 F for vessel 3D and about 340 F for vessel 3B on the afternoon of July 18, 1977.

What was done to correct? Answer: The licensee isolated the adsorber vessels and bypassed the offgas flow to the stack on the afternoon of July 17. The licensee was still able to remain well within technical specification for airborne releases with the

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adsorber beds bypassed. All release via the stack were contin-uously monitored. In order to aid in reducing the adsorber bed heating, a nitrogen purge was placed on the adsorber vessels. The adsorber vault HVAC system also acted as a heat sink for the heat released from the vessels. The licensee emphasized to the inspector that priority would be given to the investigation of the cause of the heating and that the Commission would be apprised of the findings.

6. What was si nificance? Answer: There appears to be no significant radiological health or environmental protection consequences as a result of this incident. A review of airborne releases from the plant stack during the period in which the incident occurred showed no significant increase in activity. Sampling and monitoring results for airborne particulate, iodine, and gaseous effluents showed that these effluents were well within technical specification limits. Also, preliminary results from the licensees environmental air sampling program provides no indication of increased activity about the site which could be associated with the incident.