ML20147E692

Informs of Failure to Perform Shield Survey at Power After Removing Wooden Plug & Incomplete Closing of Lead Shutter on Beam Port 2 Following Insp of Beam Tube

ML20147E692
Person / Time
Site:	Oregon State University
Issue date:	03/12/1997
From:	Dodd B Oregon State University, CORVALLIS, OR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9703180197
Download: ML20147E692 (6)

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RADIATION CENTER OntcoN STATE Umvenstry 100 Radiation Center, Corvallis, oregon 97331 5903 l Telephone 541737 2341 Fax 541737-0480 l l

March 12,1997 l

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U.S. Nuclear Regulatory Commission Document Control Desk l Washington, D.C. 20555 a

Reference:

Oregon State University TRIGA Reactor (OSTR)

Docket No. 50-243, License No. R-106

Subject:

Self-Identification of a Violation of NRC Regulations 4

Gentlemen:

This purpose of this letter is to report a recent incident in which there was an apparent violation of 10 CFR 20.1902. It is our belief that there is no regulatory requirement to report this event; however, we are doing so to demonstrate our commitment to eliminating such events, and to maintain the open and cooperative nature of our relationship with the Nuclear Regulatory Commission. An initial verbal notification of these events was made to Mr. Alexander Adams Jr., the OSTR's Project Manager at the NRC, on March 5,1997.

Background Information Since the late summer of 1996 the OSTR had been experiencing a small water leak out of the thermal :  !

column and to a lesser extent into beam port #2. The Radiation Center staff has recently completed /9 construction of a stainless-steel lining of the bulk shield tank with the objective of solving this /

problem. As part of the evaluation of the effectiveness of the lining, a protocol has been approved )

for routine inspection of the thermal column and the beam ports for signs of moisture. , gv () / '

Beam port #2 has two shield plugs: an inner plug (made of boral, lead, borated concrete and steel),

and an outer wooden plug. In addition, each of the beam ports has a four inch thick sliding lead shutter which is operated via a detachable rod and handle, and an outer, lead-lined steel door. Beam port #2 has no experiments associated with it and is therefore normally in a shut-down configuration.

This means that the opening and closing rod cannot be attached to the shutter without unlocking and opening the beam port door and reconfiguring the socket into which it screws. Beam port #2 points to the northeast.

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, U,S. Nuclear Regulatory Commission Page 2 March 12,1997 Description of the Incident On October 29,1996 water was observed for the first time leaking from the beam port #2 door.

Therefore, the beam port was opened up for inspection the following morning. This revealed a significant pool ofwater behind the door where the sliding shutter sits as well as water inside the tube itself. Removal of the wooden plug showed that parts ofit were saturated and that it had started splitting. Therefore, it was decided to leave the wooden plug out to prevent it from possibly swelling to the point ofjamming and to allow it to dry out. The plug was placed on absorbent paper on the floor outside the beam port and an area around it was roped off. Gamma and neutron surveys were performed during this process, however the neutron measurements were not recorded on the survey sheet. Apparently there was no subsequent radiation survey performed around the beam port once the reactor was started up and raised to power. Daily beta / gamma radiation surveys performed in the reactor bay did not reveal any anomalous readings.

On the moming ofFebmary 24,1997 the routine thermal column and beam port 2 inspections were performed and 5 ml of water was found in beam port #2. The Reactor Supervisor decided to open the rod vent valve to dry the beam port. The shutter was closed and the beam port door shut. At 0930 the reactor was brought to a power level of 1 MW. At about 0937 the Reactor Supervisor was in the reactor bay performing a post startup walk around when he noticed an elevated count rate on a GM detector situated on a table in the northeast area of the bay. There was a lead pig nearby and he suspected that a sample had been left in the pig. An ion chamber reading of 42 mR/h was measured at this location.

The Reactor Supervisor requested that the Reactor Operator call the Acting Senior Health Physicist (SHP). The SHP did not know of the sample, but came to the bay with a health physics student and performed a survey. Other staff were called with respect to the pig, but no-one knew what samples might be in it. On opening the pig there appeared to be some particulate matter in it; therefore the SHP moved the pig to the sample handling area in order to check it for contamination. In this location the dose rate on the pig was negligible. The Reactor Supervisor then realized that the radiation was from beam port #2, so he asked the SHP to survey the face of the beam port door, The SHP measured 350 mR/h at the face and 50 mR/h at a distance of about 4 feet from the door. The Reactor Supervisor pushed the shutter handle and gamma dose rate dropped to nonnal. The Reactor Supervisor notified the Reactor Administrator who decided that reactor operation could continue since no over exposure had occurred, and since the shutter was now closed.

Access to the reactor bay is positively controlled at all times, vith the only persons present during this time on February 24,1997 being the Reactor Supervisor, the Acting Senior Health Physicist and the health physics student assistant. The elevated dose rates had been in existence for a total of 40 minutes, and the maximum personnel radiation dose from this period as measured on direct-reading pocket dosimeters was I mR.

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, U.S. Nuclear Regulatory Commission ,

Page 3 l 4

March 12,1997 A subsequent, controlled reconstruction of the event determined that the lead shutter had not been l' completely closed and that it _was covering about five inches of the eight inch diameter tube. The reconstruction enabled radiation dose rates to be measured at a number of additional locations.

4 However, only gamma radiation measurements were taken at this time.

! On March 3,1997 the annual neutron survey of the reactor was performed and elevated readings I i observed in the vicinity of beam port #2. Additional gamma and neutron surveys provided the i following dose rates with the reactor at 1 MW:

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JMaxfFossiblei l gg j(Gamma

_ Neutron LTotal Dose < ggg gy.

t mrem /h): .

. (mrem /h);; < Rate (mrem /h):i 1 - '

y(mrem).. i

, Normal Configuratica: All Shield Plugs Inserted, Shutter and Door Closed (March 5,1997) 0.16 0.05 0.21 0.21 BP Door l

Outside Bay l Double Doors 0.04 0 0.04 .0.04 At Fence 0.009 0 0.009 0.009 Without Wooden Beam Plug /I,ead Shutter Completely Closed i (Oct. 30,1996-Mar. 4,1997) i

30 cm from 6 70 76 76 BP#2 Door-

Outside Bay 0.45 7.5 8 8 L Double Doors i

l At Fence 0.019 0.2 0.2 0.2 4-i .

j Without Wooden Beam Plug / Lead Shutter Partially Closed for 40 Minutes j (Feb. 24,1997) i- Outside Bay 15 28 43 31-Double Doors At Fence 0.7 2 2.7 1.8

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, U.S. Nuclear Regulatory Commission Page 4 March 12,1997 The area inside the reactor bay does not pose a problem under either of the two situations above. In j the first instance the maximum possible dose deliverable in any one hour was 76 mrem and the reactor bay is posted as a radiation area. On February 27,1997 during the 40 :ainutes that the reactor was l l at power with the lead shutter partially closed, the high radiation area was under continuous direct l

l surveillance capable of preventing unauthorized entry (10 CFR 20.1601(b)) and therefore did not

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require posting.

l From the data given above, it can be seen that it was possible to receive a dose greater than 5 mrem in an hour in the area just outside of the reactor bay double doors and inside the fence under both situations. This area is not posted as a radiation area. Therefore this appears to be a violation of 10 CFR 20.1902.

When the lead shutter was partially closed, there was a dose rate of 2.7 mrem /h at the fence, however this was only in existence for 40 minutes and therefore the maximum possible dose in the unrestricted area was 1.84 mrem (2.7 mrem /h for 40 minutes and 0.114 mrem /h for 20 minutes).

Cause of the Occurrences The failure to perform a shield survey at power after removing the wooden plug was apparentlyjust a complete oversight by otherwise very capable and competent staff. Staff;nembers who had not been directly involved that day had assumed that such a survey had been performed. It is probably true that health physics and operations personnel had a mind set that was focussed on the water leak as-being the primary problem with which they were currently dealing. It certainly was a good decision to leave the wooden plug out of the beam tube, but clearly a neutron survey at power would have indicated the need for some additional compensatory shielding in its stead.

The cause of the occurrence on February 24,1997 was the incomplete closing of the lead shutter on beam port #2 following an inspection of the beam tube. The lead shutter is fairly heavy and since it is not frequently used it can be stiff to close. The subsequent reconstruction of the event confirmed that none of the installed area radiation monitors showed elevated readings because of the collimated nature of the beam. Therefore, there were no indications of the incomplete closing to the operator as the reactor was brought up to power.

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, _ U.S. Nuclear Regulatory Commission Page 5 March 12,1997 i

I Corrective Actions

1. The now dry wooden plug was replaced in the beam port. It will need to be removed each time the beam port is inspected for moisture.

2. The lead shutter was closed as soon as it was recognized that it had not been completely shut.

Measures to Prevent Recurrence of Such Events 1, Procedures will be revised to require the verification of the status of experimental facilities by a second person other than the one directly involved in making any change to the status. l This will ensure positive confirmation that shutters are closed, samples loaded or unloaded, l graphite stringers replaced and the like.

2. All licensed reactor operators will review the procedures associated with opening and closing beam ports.

3. In order to provide greater knowledge and familiarity with the reactor, the Radiation Center's health physics staff will now participate in all modules of the reactor operator requalification training.

4. The lead shutters for beam ports #2 and #4 have been lubricated to make them easier to slide.

Beam ports #1 and #3 are permanently set up for neutron radiography and are inaccessible for lubrication.

5. Reactor operations, health physics and management staff held a meeting on March 4,1997 in which it was agreed that flirther cooperation and mutual support would be beneficial in helping prevent further such events.

While not necessarily a preventive measure, it was also decided to purchase a new, more portable remmeter to enable neutron dose rates at elevated locations to be more easily measured.

, U.S. Nuclear Regulatory Commission Page 6 March 12,1997 Conclusions i

In conclusion, we would like to point out that while we regret their occurrence, the events reported  !

here were promptly corrected once identified, and did not result in any personnel exposure above routine levels. In addition, we believe that sufficient measures have been taken to prevent the re- i occurrence of such events in the future. Should there be questions regarding the information in this l report or should you require more information, please let me know.

I urs sincei ly, r b l 1

Brian Dodd, PhD l Director c: Al Adams, Senior Project Manager, Non-Power Reactors and Decommissioning Projects Directorate, U.S. Nuclear Regulatory Commission, M.S. 0-11-B-20, Washington, D.C. 20555 Regional Administrator, USNRC, Region IV,611 Ryan Plaza Drive, Suite 400, Arlington, TX 76011-8064 Oregon Department of Energy,625 Marion Street, NE, Salem, Oregon 97310, Attn: David Stewart-Smith G. H. Keller, Vice-Provost for Research and International Programs S. E. Binney, Chairman Reactor Operations Committee J. F. Higginbotham, Reactor Administrator D. S. Pratt, Senior Health Physicist A. D. Hall, Reactor Supervisor

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