ML20215B194

Discusses 861211 Event Re Stack Dilute Fan & Core Vent Fan Secured by Actuation of Evacuation Alarm & Evacuation Alarm/ Core Vent Sys Interlocks White Stack Count Rate Approx 300 Cps

ML20215B194
Person / Time
Site:	05000083
Issue date:	12/19/1986
From:	Vernetson W FLORIDA, UNIV. OF, GAINESVILLE, FL
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20215B127	List: ML20215B125 ML20215B161 ML20215B194
References
NUDOCS 8706170252
Download: ML20215B194 (4)

Text

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.c.v m oso u Ac m - ci, NUCLEAR FACILITIES DMSION g -

4UCLEAR REACTOR flUtt.DlNc 1 AIM 5YlLLE. FLORIDA 326:1 UNIVERSITY OF FLORIDA g ,

910Nt (M4))924429 TELtx 54310 *

• Nuclear Regulatory Commission December 19, 1986 Suite 2900 101 Marietta S treet, N.W.

Atlanta, GA 30323 A tten tion: ,J. Nelson Grace Regional Adminis trator, Region II Re: University of Florida Training Reactor (UFTR)

Facility License R-56; Docket No. 50-83 Gentlemen:

on December 12, 1986 following discovery of the problem . outlined in the scena-rio caction below, Mr. Larry Meller of Region II was contacted and given a '

verbal description of events. In general, Mr. Meller agreed with the staff evaluation including the determination that the event is a potential violation of our Technical Specif.1 cations and hence a promptly reportable event as spe-

. cified in the reporting requirement of paragraph 6,6.2(3) of the UFTR Techni-cal Specifications.

Mr. Meller recommended that all evaluations be performed as for a technical specification violation. Therefore, this report is- being transmitted the occurrence. to meet the tech spec requirement for a final report closing out SCENARIO At 1037 hours0.012 days <br />0.288 hours <br />0.00171 weeks <br />3.945785e-4 months <br /> on Thursday,11 December 1986, the stack dilute fan and the core

- vent fan were secured by actuation of the evacuation alarm and the evacuation alarm 300 cps. / core Thevent countsystem interlocks rate was due while the stack count rate was approximately to a normal Argon-41 vent and stack inventory buildup established by a prior run starting at 0923 and secured at 1018 (100 kWth operation from 0956 to 1016).

The automatic evacuation occurred as part of the Quarterly Evacuation Drill, (Surveillance Q- 3) for which the scenario involved two area radiation monitors indicating mrem /hr).

radiation levels greater than the high level trip setpoint (10 Establishment of the two area monitors at the high level trip set-point initiated the core vent / diluting fan interlock with the evacuation alarm as required tions, Section by 3.4.3, Technical Specifications. However, UPTR Technical Specifica-s ta tes:

m 3.4. 3 Reac tor Vent Sys tem con:

fNCA

$9D- The reactor vant system shall be operated at all times dur-C So ing reactor operation. In addition, the vent system shall

. g:g be operated until the stack rnonitor indicates less than 10 counts per second (cps). Whenever the reactor vent sys tem

'Q oc is opera ting , air drawn through the reactor vent sys tem

@ shall be continuously monitored for gross concentration of g radioactive gases. The output of the monitor shall be indi- i 5A cated and recorded in the control room. The reactor vent N system shall be immediately secured upon detection of: a failure in the ronitoring system, a failure of the absolute filter, or an unanticipated high stack count rate.

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Nuclear Regulatory Commission 1 December 19, 19Q6 i Page Two f y

L l EVALUATION -, >

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. subsequent discussions of the event .when discovered in d1e af ternoon (~1500 hours) Triicated that the high count rate with the core vent system secured could con stitute a violation of Technical Specifications. In assessing the 1

consequences of. a potential violation of Technical Specifications, the impact of the action on the premise or the bases of the Limiting condition for Opera-  !

tlon (LCO) must be considered. This LCO is unusual in two respects.

, 1 First, there is no indication of the bases for the LCO. Discussions with the q UFTy Staff indicate that the LCO is based on ,the potential' for activated Argon j gas jexfiltrating into static atmosphere of the UFTR cell as well as buildup of j

radtn from natural causes within the cell. A review of the recorder charts for the' Air Particulate Detector (also alarmed for this drill scenario) and for 4 1

the Area Radiation Monitors traced during the conduct of the drill shows no I 3 effect upon radiological conditions of the UFTR.

The second relate unusualthe to operating aspect rv of this LCO is that the required condition does not i

l down condition. As such ss%n 'or, but is a requirement imposed during a shut- i rence as the reactor a Ton of this LCO may not be a reportable occur-

- op, ting. This LCO also appears to be in conflict s

with the requirements e ven t sys tem, and th , ' -

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>acuation alarm automatically secure the core f 1

tor or failure of tue .e , vent system be secured on a loss of stack moni-nt absolute filter.

CONSEQUENCES 1

Argon-41 production cannot be increased through this action of securing the vent system, and the effluent concentration for the duration of this event ac- l tually had to decrease as the core vent damper closure dbat ' occurs with secur-ing the core vent fan stops air flow from the reactor. j tive impact to radiological or reactor systems could or did occur from thisThe fact that ( n  !

> event supports the evaluation that this event posed no potential for compro-mising reactor safety or the health and safety of the~ public.

These evaluations were reviewed individually with members of the Executive i l

Committee of the Reactor Safety Review Subcommittee (RSRS) on December 12, 1986 prior to enntacting Mr. Meller and then' again in a formal meeting of the Executive

{

Committee of the RSRS cn Decenber 12, 1986. i A

CORRECTIVE ACTION /RECONMENDATION i

Since this event represents a potential violation of Technical Specifications, '

the' RSRS recommended that this event be reported to the NRC as was done on

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December 12 and finalized with this report. Corrective action for the specific problem of securing the vent at >10 cps on the stack monitor during a drill will be assured by requiring that all drills be conducted prior to running the UPTR at power levels above 500 watts on the day of the drill and/or assuring the s tack monitor is reading below 10' eps prior to drill initiation with a checkoff on the drill scenario card which will be added to Standard Operating L

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\ -i Nuclear Regulatory Comm'ssion - .

December 19, 1986 Page'Three Procedure 0.5 as an additional part of the Q-3 drill form. This corrective  ;

action will be implemented prior to. the next quarterly radiological emergency drill due in March, 1987.

The RSRS at its regular meeting on December 19 required a proposed Tech Spec change to be developed on the requirement. for core vent system operation with stack monitor count rate above 10 cps; af ter re-evaluation and with support on a technical basis, Section 3.4.3 will be modified so that the requirement for not securing the reactor vent sys tem above 10 cps can be modified, perhaps with only a recommendation that it not be secured above 10 cps. This change will be based upon the lack of safety and/or radiological effects from secur-ing the reactor vent system for'short periods of time or even with a higher )

i stack count rate. This tech spec change will eliminate the conflict involved in securing the vent fan system for an actual emergency following a reactor run should such occur; this work will be completed by May 30, 1987; a subse- "

quent request for a tech spec change will then be submitted.

FINAL I40TE The RSRS Executive Committee members 'were contacted on December 12,1986 rela-

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tive to the securing of the reactor vent system. The members of the RSRS Exe-cutive Committee all agreed that the incident had no impact on reactor safety -

or the health and safety of the public. Therefore, the UFTR was granted per-ndssion to commence normal operations as of December 12, 1986. A formal uset-ing of the Executive Committee was convened to document this permission.

As a further note, the full RSRS met at its regularly scheduled meeting on De-cember 19, 1986 and unanimously supported the additional check on the drill scenario card and the proposed change in the tech ~ specs required as corrective action by the RSRS Executive Committee and the UPTR staff and included in this

, report.

• N> bh this report this incident is considered closed with corrective action to be implemented as noted above.

Since rely, M M S1h William G. Verne tson Director of Nuclear Facilities WGV/ps cc: Reactor Safety Review Subcommittee

. P.M. Whaley, Acting Reactor Manager

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ATTACHMENT IV l

1. Dimensions and free air space:

l 3

a. Cell Volume: 60' x 30' x 29' = 5.22 E 5 ft

b. Control Room Volume not accounted for:

3  !

14 ' x 9 ' x 8 ' = 1.0 E 3 ft

c. Pit Volume: 5'3" x 13'6" x 6' = 425 ft 3 j

d. Reactor volume l

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1. Elongated octagon = ellipse .]

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Major axis 20 '4", minor axis 15 ' 6", height 11 ' 10. 5" .;

Reactor Volume: 2993 ft 3

2. Rectangular parallelapiped, same dimensions Reactor Volume: 3742 ft3 - more conservative

2. Total Free Cell Volume: la + 1b + 1c - 1d(2) = 5.2 x 105 ft 3  ;

3. Freevolumeinreactor(voidsgaces) is estimated at 1% effectively -

considered conservative: 38 ft

4. Dilution factor for concentration in void spaces:

Free Reactor Volume Item 3 Dilution Factor = = 7. 3 x 10'5 Total Free Cell Volume " Item 2

5. Normal (full power) average concentrations in void spaces implied from core vent effluent at 12 x 10-4 pCi/ml.

6. Therefore, the cell avereage concentration would be:

12 x 10-4 pCi/ml x Dilution Factor = 8.8 x 10-8 pCi/ml where a major conservatism is the assumption that all the radioactive Argon-41 gas is immediately released into the free cell volume with no delay and no decay.