ML20082D022

Ro:On 950309-13,leakage of Coolant HX Occurred After Primary Coolant Resistivity Increase Noted.Primary & Secondary Flow Secured & Shell Side of HX Drained.No Leakage Collected.Hx Returned to Primary Sys & Placed in Operation

ML20082D022
Person / Time
Site:	05000083
Issue date:	04/03/1995
From:	Vernetson W FLORIDA, UNIV. OF, GAINESVILLE, FL
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 9504070247
Download: ML20082D022 (5)

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UNIVERSITY OF -

FLORIDA Nuclear Reactor Facility 202 Nuclear Sciences Center Department of Nuclear Engineering Sciences P.O. Box 118300 Gainesville, Florida 32611-8300 L Tel: (904) 392-1429  ;

Fax: (904) 392-3380 April 3,1995 i

14 Day Report:

Leakage ofPrimary Coolant Heat Exchanger Regional Administrator, Region II U.S. Nuclear Regulatory Commission t 101 Marietta Street, N.W., Suite 2900 Atlanta, GA 30323

Dear Sir:

Re: University of Florida Training Reactor .

Facility License: R-56, Docket No. 50-83 Pursuant to the reporting requirements of paragraph 6.6.2(g) of the UFTR Technical Specifications, a description of what was originally considered a potential violation of the Technical Specifications was reported by telephone /telecopy (Attachment I) on March 14,1995 and a 14 day written report is submitted with this letter including occurrence scenario, NRC ,

notification, evaluation of consequences, corrective action and current status. The potentially promptly reportable occurrence involved the decrease of primary coolant resistivity, originally leading management to hypothesize a leakage of the primary coolant heat exchanger. This 14 day written report is delayed one week per agreement with Mr. Ed McAlpine of Region II  !

in a telephone conversation notifying of plans to restart.

Scenario On March 9,1995, a one-hour full power run concluded at 1416 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.38788e-4 months <br /> with all indications normal. At 1715 hours0.0198 days <br />0.476 hours <br />0.00284 weeks <br />6.525575e-4 months <br />, Reactor Manager D. Simpkins and SRO D. Cronin observed a red indicating light on the Primary Coolant Resistivity Solu-Bridge. Upon investigation, the primary coolant resistivity was found to be 0.25 MD-cm. This was thought to be a potential crud burst ,

I from the reactor operation at full power since a calorimetric had been performed the previous day and power adjusted. As is standard practice, the well water secondary cooling was secured and the city water cooling initiated. On March 10,1995, at 0915 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.481575e-4 months <br /> SRO D. Cronin informed the Reactor Manager (at home) and the Facility Director the primary coolant l demineralizer inlet resistivity was 0.5MD-cm, while outlet resistivity was 1.2MD-cm. Normal Il 9504070247 950403 PDR ADOCK 05000083 S PDR  ;

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,Regiorial Administrator, NRC Region II Page 2 i April 3,1995 l l

levels are 1.0MO-cm or higher. Pit radiation levels were verified to be normal, and a primary pit entry was performed to obtain a primary coolant grab sample. Portable resistivity meter  !

readings were 0.6MD-cm, correlating with the in-line solu-bridge. At 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />, the primary resistivity was reported as 0.7MD-cm. The concern at this point was that there could be a fuel element leak. At 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br />, primary resistivity had increased to 0.8M0-cm and was continuing to rise. Gamma spectroscopy with HPGe detectors indicated the normally present Na-24, but no other radioisotopes, including fission products, were detected. Gross #Sy activity was j 7.46x104 Ci/ml, while alpha activity was less than the lower limit of detection (LLD) for the  !

system used. These values are normal, indicating the resistivity problem was new and  ;

apparently had not occurred during operations to provide significant activation levels. At 1500 l hours, primary resistivity had increased to 0.9MO-cm, and outlet resistivity had remained at  !

1.2MD-cm. Primary and secondary cooling was secured for the weekend, but demineralizer flow was left in the normally-on condition with the problem apparently alleviated. 1 On Monda , March 13,1995, the weekly preoperational checks were performed. The primary inlet and outlet resistivities were 1.3MD-cm, verified by portable resisdvity meter checks.

Primary and secondary flow was secured at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> upon satisfactorily completing weekly and daily checks prior to normal operations. At 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, well water secondary cooling was initiated to determine if the secondary water would cause a decrease in primary resistivity with demineralizer flow only. At 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />, primary flow was established to expedite any decrease in primary resistivity. At 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br />, primary resistivity decreased to 0.8MD-cm, and secondary cooling was secured. Primary flow was left in operation to facilitate coolant cleanup.

At 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />, primary resistivity was 0.7MO-cm, and MLP #95-12 (Primary Coolant Resistivity Drop) was opened and the gate valves for the city water supply, the well water supply and the heat exchanger drain were isolated. Primary and demineralizer flow was also secured until further investigations could be performed since a heat exchanger leak was now suspected.

Primary Coolant Storage Tank levels were compared to recent weekly survey results and found to be consistent indicating limited if any in or out leakage. Water samples from the Secondary Sample Tank were analyzed with negative results indicating no environmental effects ifleakage had occurred.

At this point the Reactor Safety Review Subcommittee (RSRS) Executive Committee convened to review the occurrence. The fact of no fuelleakage and the verification of apparent heat exchanger leakage on March 13, 1995 and its possible prompt reportability per UFTR Tech Specs Section 6.6.2 Special Reports, Paragraph (1) and Paragraph (3)(c) was discussed. It was noted that preliminary radioactivity measurements and surveys did not indicate there had been a release of radioactivity to the environment based on secondary side heat exchanger and sample l tank measurements; however, there was thought to possibly be a " degradation in the coolant l boundary." Because secondary pressure is higher on both secondary systems (well or city water), any leakage should have been into the primary when the secondary was running. Since I

Regional Administrator, NRC Region II

'Page 3 April 3,1995 the decrease in resistivity occurred nearly three hours after the last operation and since the primary sample was free of unexpected radionuclides, it was noted that this is clearly a new problem and not one that was occurring during reactor operations which had been suspended until the heat exchanger would be returned to service. It was noted that all flow systems were secured along with block valves on March 13, 1995 to assure no leakage from the primary system though the primary coolant storage tank level was noted to be commensurate with expected levels and the primary coolant resistivity decreases rather slowly and the demineralizer continues to have output with resistivity in excess of 1.0 megohm-cm, all indicating any leak would apparently be small.

The committee also reviewed planned actions and approved proceeding as follows:

1. Check the heat exchanger and confirm maximum leakage rate; then confirm leakage by pressure test if necessary.

2. Assuming a leak is confirmed, determine whether we can implement repairs. If yes, then proceed. If no, then check on getting it fixed or probably replacing it with a 10 CFR 50.59 evaluation and determination needed since the company who made this heat exchanger is no longer in business and it has been in service close to 20 years and is N-stamped.

During the meeting, prompt notification of the NRC was recommended.

NRC Notification After the RSRS Executive Committee meeting on March 14,1995, NRC Region II was informed of this event per a telephone conversation on March 14,1995 with Mr. Ed McAlpine relative I to the potential leak of the heat exchanger. The situation was confirmed in a following fax transmittal (Attachment I). At this time the potential failure was described and the key Tech Spec sections were reviewed. There was also agreement to treat the event as reportable.

In a subsequent conversation on March 24,1995, Mr. Ed McAlpine of Region II was updated on the system status including removal and replacement of the heat exchanger with no leaks i detected plus replacement of the demineralizer resins as a possible ionic source to the primary coolant with all systems verified operating properly and no resistivity problem noted. Later on  ;

March 24, Mr. McAlpine was informed of plans to restart per the RSRS approval to introduce l temperature on the system and clean up any ionic contamination released as well as complete a radiation survey nearing its overdue date. Mr. McAlpine was informed of the expectation that there might be a resistivity drop upon restart since the system had been opened twice but it should recover quickly.

, Regional Administrator, NRC Region II Page 4 April 3,1995 Evaluation / Corrective Action To address a possible heat exchanger leak, Maintenance Log Page MLP #95-12 and Radiation Work Permit RWP 95-1-I were opened to investigate the primary coolant resistivity drop and to control testing of the Secondary Heat Exchanger for leakage. On March 15,1995, the shell side of the heat exchanger (secondary cooling supply) was drained and the primary system placed in operation. No leakage was collected from the tube (primary coolant) side. On 2 March 17,1995, the tube side of the heat exchanger (primary coolant supply) was drained and 4 the shell (secondary cooling) side was placed in operation with city water supplying. The drain valve on the shell side of the heat exchanger was closed to place city water pressure on the heat exchanger. No leakage was collected. The city water supply was then secured and the well pump placed in operation. At shut-off head, there was no leakage collected. The heat  !

exchanger was then fully drained and removed from the system. On March 20,1995, the i secondary side of the heat exchanger was pressurized with 40 lbs. of nitrogen gas overnight with no decrease in pressure. On March 21,1995, the pressure was raised to 60 lbs., but with no pressure reduction over several hours. On March 22,1995, the heat exchanger was returned  ;

to the primary system and placed in operation, with well water supplying secondary cooling.

On March 23,1995, the primary coolant inlet and outlet resistivities were normal at 1.0 MD-cm, i respectively. l After the heat exchanger was returned to the system, MLP #95-12 was utilized along with a newly opened RWP 95-2-I to replace the primary demineralizer resins on March 23,1995, since this was the only other possible source for coolant contamination to decrease resistivity. After replacement of the resins, the system was closed up and all resistivity readings were noted to j be normal. Subsequently, a restart and operation at power was conducted with all indications )

normal and the coolant soon reaching 1.3MO-cm resistivity on the inlet to the demineralizer system.  ;

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Current Status /Consecuences Following successful testing of the heat exchanger and demineralizer resin replacement, this problem is considered resolved. The system is operating normally. The source of the resistivity j drop is not known but suspected to be some sort of release from the demineralizer resins which  !'

had been in service for over four years.

As indicated, the RSRS Executive Committee met on March 14,1995 to review this event and then again on March 23,1995 to approve restart operations after checks were negative on the heat exchanger and the primary coolant resins were replaced. The Committee essentially agreed with actions taken and with the initial staff evaluation that the occurrence did represent a potential violation of the UFTR Technical Specifications and was promptly reportable if a heat exchanger leak were involved. After this possibility was eliminated, the event is likely not

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April 3,1995 i

promptly reportable. Reactor Management and the RSRS Executive Committee agree there has  :

been no significant compromise to reactor safety in the occurrence and no impact on the health j and safety of the public. Other than considering the event in the next regular RSRS meeting, this occurrence is now considered closed.

If further information is needed, please advise. j Sincerely, M

William G. Vernetson I Director of Nuclear Facilities WGV/dms [

Attachment .

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Copies: U.S. NRC Document Control Desk Ted S. Michaels, NRC Project Manager Reactor Safety Review Subcommittee  !

D. Simpkins, Reactor Manager .

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Sworn and subscribed this dut day of April,1995.

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WY COWASSION 8 CC302416 EXPlRES August 27.1997 soNoto mnote em esVMNCE,NC i

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, UNIVERSITY OF FLORIDA Nuclear Reactor Facility 202 Nuclear Sciences Center Department of Nuclear Engineering Sciences P.O. Box 118300 Gainesville, Florida 32611-8300 Teh (904) 392-1429 Fax: (904) 392-3380 March 14,1995 U.S. Nuclear Regulatory Commission Potential Tech Spec Violation -

Region II Irakage of Primary Coolant 101 Marietta Street, N.W., Suite 2900 Heat Exchanger Atlanta, GA 30323 Attention: Stewart Ebneter, Regional Admmistrator Re: University of Florida Training Reactor Facility License: R-56, Docket No. 50-83 As per the telephone conversation of March 14,1995 with Mr. Ed McAlpine relative to a probable leakage of our primary coolant heat exchanger on March 9,1995 with probable verification on March 13,1995, we have concluded this occurrence is a potential abnormal occurrence and a potentially reportable occurrence per UFTR Technical Specifications, Section 6.6.2 delineating requirements for special reports. The RSRS Executive Committee has met and recommended NRC notification as per Section 6.6,2 of the UFTR Tech Specs as a potentially promptly reportable occurrence. Initial evaluation indicates the heat exchanger has a smallleak due to decreasing resistivity of the primary coolant registered when the secondary coolant is flowing. Preliminary radioactivity measurements and surveys do not indicate that there has been a release of radioactivity to the environment. It should be noted that the reactor has not been run since this problem was noted and was discove' r ed during a shutdown period on Mzrch 9, 1995.

Sincerely,

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William . Vernetson Director of Nuclear Facilities WGV/dms p%, ,o Copies: D. Simpkins -

' ~ " "T r r 7, RSRS Sworn and subscribed this 17 day of March,1995.

JOAN MOREHOUSE (L%u , ,

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MY cowx5 son a CC3 416 EXPIRES M us:27.1997 Notary %blic Equal Oppor' unity /Affirmatis e Action Institution