ML20197D275

Ro:On 971026 & 1106,slight Elevation of Fission Products Were Detected in Primary Coolant Water Analyses.Caused by Slight Fabrication Flaw in Element MO-460.Surveillance of Bwx Technologies Fabrication Techniques Will Be Increased

ML20197D275
Person / Time
Site:	University of Missouri-Columbia
Issue date:	12/15/1997
From:	Mckibben J, Meyer W MISSOURI, UNIV. OF, COLUMBIA, MO
To:	NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9712290021
Download: ML20197D275 (3)

Text

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[ .. Rssearch Reactor Center -

Research Park Columbia. Missouri 65211 II ,

Telephone (573) 882-4211 FAXi573]882=3443

UNIVERSITY O# MISSOURl-COLUMBIA -

December 15,1997.

Director of Nuclear Reactor Regulation ATTN: Document Control Desk Mail Station F137 US Nuclear Regulator Commission Washington, DC 20555 REFEltENCE: Docket No. 50-186 University of Missouri Research Reactor License R.103

SUBJECT:

Slight elevation of Gssion products detected in primary coolant water analysee

= BTI'HODUCTION The University of Missouri Research Reactor is reporting the detection of a slight elevation of I 131 in the weekly primary coolant analyses required by Technical Speci6 cation 5.2.c

- for the weeks of November 3 und October 20,1997. Typical concentrations of I-131 in the weekly samle analyses are 1.3 r 10 5 to 1.5 x 10 5 pCi/ml. Samples tnken October 26 and November F indicated a concentration of 1-131 of 2.3 x 10 5 pCi/ml. ibis concentration ofI.

- 131 indicates a slight increased level of Ossion products in the primary coolant, but is a factor of 200 less than the Technical SpeciGcation limit for 1-131 of 5 x 10-3 pCi/ml in Technical Speci0 cation 3.9.c. This report is made for informational purposes because the literal interpretation of abnormal occurrenen as denned in Technical Speci6 cation 1.1.d does not specify a threshold for release of Gssion products from a fuel slement even though the concentrations of1131 detected were far below the Technical SpeciGcation Limiting Conditions for Operation.

DESCP.ll' TION Reacto. primary coolant water is sampled and analyzed each week of reactor operation as specided in Technical SpeciGcation 5.2.c. The primary coolant spectroscopy results on the Novtmber 5,1997 sample indicated normal levels ofI-131, but other iodine isotopes were slighsly increased. This analysis coincided with elevated readings on the on-line fission product monitor (PPM) which continuously monitors primary coolant activity. The fission product monitor typically indientes 3000 to 5000 counts / minute. During the week of November 3 the indication increased ta 12,000 to 15,000 counts / minute.

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Additional primary coolant ramples were taken November 6,7 and 8 to monitor 1131 concentrati3n in the primary coolant water to assure we were well below the Technical y

Specification Liniiting Conditions for Operation of 5 x 10 3 pCi/ml (T.S. 3.9.c). The '

'snmple analysis on November 6 indicated an 1131 concentration of 1.6 x 10 5 pCi/ml. g3 Other Gssior -roducts were abo detected in these samples at low levels (i.e., slightly i ater than .ninimum detectable activity).

, , n V 9712290021 971215 PDR ADOCK 05000186'-

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i Letter to Dir:etor of Nuclear Itcartor llegulation

- December 15,1997

_ Page 2 Review of previous primary coolant analyses indicated an earlier slight increase in 1131 concentration on October 20,1997. This sample was taken to investigate a slight increase in the fission product monitor indication (about 2000 to 3000 countdminute above normnD.

The results of the 1131 sample on October 20 indicated a concentration of 2.3 x 10 5 pCi/ml, which was considered to be within statistical variation of the en ected concentration because the concentrations were so close to minimum detectable activity.

On November 6, the primary chemist reviewed tha core loadings for the previous three weeks and was able to determine that two fuel elements, MO-458 and MO 460, were common to the cores that ran the weeks of November 3 and October 20,1997, whtn increased b131 concentrations were found. These two elements had accumulated a power history of 126 MWD cach at the end of reactor operation at 0400 on November 10,1997. The Itenctor Manager pinced these elements in the retired category and scheduled them for post irradiation ihspection, Fuel elements MO-458 and MO-400 were stored in pool storage racks a distance apart so that grab samples of pool water couhl be taken ubove them to determine which element was leaking, itesults of the unalyses indicated that MO 460 was the problem element.

Both elements were inspected November 20,1997, by the procedure used for inspection of retired fuel elements. The test includes a visual inspection of the outside surface of plates 1 ,

and 24 and a visual inspection of the fuel plate gaps for any foreign material. The inspection includes a go-no go" test with a gap check tool to ensure no fuel plates have exceeded 10% swelling over their useful life an indicated in the basis far Technicti Specification 3.8.n.

Neither ch, ment indiented abnormalities that could be attributed to reactor operation with  !

partial flow blockage of a coolant chminct or excessive swelling of a fuel plate.

ANAINSIS The slightly clevate 11131 cor entre ions in the primary coolant were most likely due to a slight fabrication flav in elemsit MO 460 such as e pit in the cladding in one of the MO-460 fuel plates. Fuel elements typically operate for 150 MWD without any detectabic increase above the normal concentrations of1-131 in the primary. This element had been in the fuel cyclo since May 19pti and previous cores in which it as incorporated indicated no increases in 1 131 until the week of 0ctober 20,1F 37.

The total 1 131 activity in the primary kystem vote ne of 2000 gallons (with a concentration of 2.3 x 10 5 pCi/ml) was approximately 175 pCL This corresponds to 0.5% of the activity allowed in the primary coolaat by the Limiting Conditions for Operation in Technical Specification 3.9.c.

The slight increase in 1 131 ectWity in the primary system was not a threat to the public even if primary water had been taleased. There, in fact, wer, no indicction of elevated airborne 1131 activity during the period of time the reactor ~' operated with slightly elevated 1131 concentrations in the primary water.

For perspective, the peak 1 131 concentration indicated in the primary coolant was only a factor of 2.3 times the 10CPH20, Appendix B, Table 3 limit for release of 1 131 to the sanitary sewer.

Letter to Director of Nuclear Itenctor Readation

+ December 15,1997

• ~ Page3 The reactor operated on two occasions with slightly elevated 1-131 netivity in the primary coolant. Subsequent review of Technient Specifientions revealed that the deGnition of abnormal occurrence related to Ossion product activity in the primary coolant did not have a specific threshold, even though the concentration detected was well bel ow the Limiting Conditions for Operation. The NltC was notified by telephone the week of Novernher 17 of these pecuirences and of our intent to report in written form.

COltHECTIVlWOLLOW.UI' ACTION When the fission product monitor indiented elevated readings, additional spectroscopie analyses were taken to verify that 1131 concentrations were within the limits of Technical Specifiention 3.9.c. The primnry chemist was able to narrow the search for the source of the fission products to two elements by reviewing the elements used in each week's core.

After defueling the suspect elements to pool storage, grab samples above the elements were able to identify MO.460 as the source of the elevated fission product activity. This element and its companion clernent, MO 458, were inspected to verify there were no indientions of fuel plate swelling or foreign material hetween the plates that could account for fission product release. Ornh samples taken above M0 460 after a week out of the core indicated no elevated fission product netivity in the pool water. Lenkage from fuel elements is often undetectable when not in an operating core. Before this element is shipped to DOE na spent fuel, we will carefully monitor the in. cask lench test to ensure it is no longer leaking. We will determine if DOE requires any other special hemdling of this element before it is sent to them as spent fuel.

The fuel vendor, BWX Technologies, Inc. (formerly linhcock & Wilcox), and the program mannger for DOE's university fuel assistance program were notified of this problem. BWX Technologies also provides fuel for the Advanced Test Itenctor (ATID and no other lenkage problems have been experienced at MUllit or ATit with BWX Technologies fabriented fuel.

The program manager for DOE's university fuel procurement indiented they will increase their surveillance of IlWX Technologies' fabrication techniques to ensure high quality fuel to MUltit and ATH.

ENDOHSEMENT:

Sincerely, 1(eviewed and Approved UAkk . w Walt A. Meyer Jr J. Charles McKibben llenctor Manager Associate Director xc: Mr. Alexander Adams Jr, USNHC '

Mr. Tom ilurdick. NHC Itegion ill Dr. Elaine Charlson, Associate Provost, Mt>

Reactor Advisory Committee - fj -

Itenetor Safety Subcommittee ( j jig M ))/ h f(;ri( n/n%7 CHRISTINE M.ERRANTE Notary Public - NMary Seal  !

STATE OF MISSOURI Doone County My Commisslan Ex; ires: Al*il 14.19??

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