ML20214N838
| ML20214N838 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Columbia |
| Issue date: | 11/24/1986 |
| From: | Alger D, Meyer W MISSOURI, UNIV. OF, COLUMBIA, MO |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8612030761 | |
| Download: ML20214N838 (4) | |
Text
Research Reactor Facility UNIVERSITY OF MISSOURI g,,,g p,,
November 24, 1986 coiurnbia. Missouri 65211 Telephone (314) 882-4211 Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
REFERENCE:
Docket 50-186 University of Missouri Research Reactor License R-103
SUBJECT:
Report as required by Technical Specification 6.1.h(2) concerning reactor operation with a deflated seal on the personnel airlock inner door.
INTRODtlCTION:
Technical Specification 3.5(a) states that " containment integrity shall be maintained at all times except when:
The reactor is secured, and irradiated fuel with a decay time of less than sixty (60) days is not being handled." The Technical Specification definition of reactor containment integrity (1.15) lists six conditions which must be met for containment integrity to exist. One of these conditions is that the personnel airlock doors are operable. The Technical Speci-fication definition of operable (1.12), in turn, states "that a system is operable when it is capable of performing the intended function in a normal manner."
The reactor operated from 1728, October 30, 1986, to 0400, October 31, 1986
[a period of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 32 minutes] with the seal for the inner airlock door deflated due to the bleed valve for this seal being in an abnormal position, pre-venting inflating air pressure from reaching the seal.
In this configuration, the personnel airlock doors were capable of performing their normal opening and closing sequence, however, only the outer airlock door was fully operable with its seal capable of inflating.
Technical Specification 4.2(c) also applies to reactor containment integrity and states that "the containment building leakage rate shall not exceed 16.3 3
ft / min. with an overpressure of one pound per square inch gauge".
The ability of the containment building to pass this required leakage cri-teria with the seal for the inner airlock door deflated is not kown. The last previously measured leakage rate was 11.2 SCFM with 1 psig overpressure during performance of the annual leak rate test, May 29, 1986, with the inner airlock door gasket inflated.
h
[
s E
O gb COLUMBIA KANSAS CITY ROLLA ST. LOUIS an equal opportunity institution g
Director November 24, 1986 Page 2 For the period of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 32 minutes that the reactor operated without the inner airlock door seal inflated, reactor containment integrity was in a state of reduced effectiveness due to the inner airlock door not being fully operable and because the containment building leakage rate relative to the leakage criteria of 4.2(c) was uncertain. All the other conditions required for containment integ-rity and reactor isolation existed.
No reactor isolations were called for by the safety system during the time period that the inner airlock door seal was de-flated.
DESCRIPTION At 0400 on October 31, 1986, a reactor operator on routine patrol noticed an abnormal air flow noise in the personnel airlock to reactor containment.
Investi-gation by the operator revealed that the air bleed valve to the inner airlock door gasket was in the " bleed off" position, which deflates the gasket and prevents in-flation of the gasket. The operator returned the bleed valve to its normal posi-tion and the gasket inflated and sealed properly.
The reactor was started up at 1728 on October 30, 1986 following a scheduled maintenance day. One of the maintenance activities during that day included main-tenance on the airlock doors performed by the reactor machine shop personnel.
This maintenance required deflating the door gaskets in order to manually open both doors. At the conclusion of maintenance activities on the airlock doors, the machine shop personnel returned the bleed valve for the outer airlock door gasket to its normal position, but failed to place the bleed valve for the inner airlock door gasket to its normal position.
ANALYSIS The basis for Technical Specification 3.5(a) is to assure that the contain-ment building can be isolated at all times except when the plant conditions are such that the probability of release of radioactivity is negligible. Technical Specification 4.2(c) ensures that the building will have sufficiant integrity to prevent the leakage of more than ten percent of contained potentially radioactive air over a 24-hour period in the event of any reactor accident.
No credible accident has been identified which can result in a significant i
overpressure in the containment building. Nonetheless, if an event had occurred requiring containment isolation, the flow rate through this pathway would have been small, detectable, and easily secured by either inflating the inner airlock door seal or shif ting the doors to the outer airlock door.
It is pertinent to point out that the airlock door to gasket face clearance is small even with the seal deflated, and any overpressure in the containment building would have tended to seat the door against the seal.
The cause of this event was improper planning and followup for the mainte-nance evolution on the airlock doors. With respect to planning, the bleed valves should have been red-tagged by maintenance personnel prior to performing mainte-nance so that the abnormal position of the biced valve would have been evident to the licensed operator who would have had to clear the tags.
4
\\
Director November 24, 1986 Page 3 In regards to followup, even though the airlock door maintenance was per-formed by highly skilled machine shop personnel, they are non-licensed individuals who were not cognizant of the significance of the proper positioning of the bleed valves following their work. At the conclusion of their maintenance, the airlock door system should have been checked by licensed personnel to determine that it was operable in all respects.
CORRECTIVE ACTION An addition to the Standard Operating Procedures will be made to reflect the need for a licensed operator to check maintenance performed on reactor license significant systems and equipment, especially when the maintenance is performed by non-licensed personnel who may not be cognizant of the importance of such systems and equipment.
The requirement to red tag the bleed valves when their repositioning is re-quired for future maintenance will be addressed to the machine shop personnel and all licensed operators.
As a further control, an entry will be made in the Reactor Startup Checksheet to have the shift supervisor " Review all reactor and license related systems upon which maintenance was performed to ensure their operability."
Additionally, a second pressure gauge will be added to the air supply system for each airlock door gasket (see Figure 1). The existing gauges only measure air supply available to the gaskets and not actual gasket air pressure. The new gauges will reflect the status of air pressure in each gasket. These gauges will be checked as part of the routine patrol preceding each reactor startup as part of the Reactor Startup Checksheet.
Sincerely, Walt A. Meyer, r.
Acting Reactor Manager Endorsement:
Reviewed and Approved
( p dk.
Q
^
Don M. Alger Associate Director
Attachment:
Fig. 1 xc:
U. S. Nuclear Regulatory Commission c/o Document Control Desk
'gg James Keppler, Regional Administrator
%u min
~
US NRC, Region 111 nun eteuc suit u Mm" m m.
Reactor Advisory Committee
" j ' j $.; $ U $ c.
Reactor Safety Subcommittee
"' COAITAIMMENT 000R GASKET
"~""*3**-
~
AIR SUPPLY l85l RESEARCH REACTOR FACILITY
.geg7 f op j II UpsVER8 TTY of h5SSOURt. COLLAS4A DATE DRAWN SY APPROVED Y SCALE 21 AIOV I986 J.M. Mcgcc t0.n.
ua,,o,cau, AIR LOCK Doo ft SEQOE N C lu G CIRCulT TRAM 500CE RS I
EXISTING f*RESSURC 3 WAY IM PL ATio u/
g GAUGE DE TL ATIO N PRES $URE SWITCH
- \\\\
2 WAY BLEED VALVE A) NORMAL FostTIOM:
AIR THRO 06H VALVE To sNFLATE GA5kET Ph BLEED OPP POSITIO N:
,j PROPOSED O
,s PR ESSUR E (gg---~
AND SLOCKS 6AUGE g/_f JM FL ATING AIR Ang LetM DOOR GA% MET 1
1
_-.