ML20127F063
| ML20127F063 | |
| Person / Time | |
|---|---|
| Site: | University of Buffalo |
| Issue date: | 05/30/1985 |
| From: | Henry L NEW YORK, STATE UNIV. OF, BUFFALO, NY |
| To: | Mccabe E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NUDOCS 8506250003 | |
| Download: ML20127F063 (9) | |
Text
{{#Wiki_filter:e Btate University of NewYork at Buffalo l / N NUCLEAR SCIENCE AND TECHNOLOGY FACILITY May 30, 1985 FILE RE: Mr. Ebe C. McCabe U. S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406
Dear Mr. McCabe:
License R-77 Docket 50-57 Enclosed for your information is the report detailing the "incicien!" at the Nuclear Science and Technology Facility n May 6, 1985. This report supports our telephone conversation of May 7, 1985. If you have any questions, please give me a call at 831-2826. Yours very truly, 0d4[4 / Louis G. Henry Director amf cc: Nuclear Safety Committee Vice President Rennie W. O'Brien K. Rimawi 8506250003 850530 PDR ADOCK 05000057 },. x ~ ~ lg S PDR ROTARY ROAD, BUFFALO NEW YORK 14214 TEL.(716)8312826 (FoRMERLY WESTERN NEW YORK NUCLEAR RESEARCil CENTER. INC.)
8 tate UnIEersity of New York at Cuffalo I /N i ~ X NUCLEAR SCIENCE ANo TECHNOLOGY EACn,ITY FILE RE: INCIDENT REPORT ' Nuclear Science and Technology Facility May 8, 1985 Introduction on the af ternoon of 5/6/85, coincident f ailures of an experimental facility and an ef fluent radiation monitor necessitated a reactor shutdown and a containment building evacuation. There were no releases of radioactive materials in excess of the applicable limit. Furthermore, there were no unusual exposures to personnel or incidents of personnel contamination. Summary of Events The following is a summary of events which occurred. On 5/3/85, an experiment was loaded into the NSTF dry irradiation facility (hereafter--the dry chamber). The dry chamber is a large (7 feet) cubical chamber in the biological shield of the reactor. In order to enhance neutron fluxes within the chamber, there is a voidable hollow aluminum nosepiece between the reactor core and the pool liner adjacent to the dry chamber. In preparation for start-up on 5/5/85, the nosepiece was voided, using CO2 pressure. This procedure is performed while the reactor is subcritical because the estimated reactivity ef fect is.15% AK/K. (Negative when voided; positive when filled). The reactor was started on the af ternoon of 5/5/85. The start-up was routine. During operations with the dry chamber nosepiece voided (an occasional occurrence), the levels of Argon-41 released through the stack are elevated above the norm (nominally 5 x 10-5 pc/cc). At approximately 3:15 p.m. on 5/6/85, the indicated count rate on the building air monitor jumped from 200 cpm (20% A-41 mpc) to approximately 1,000 cpm. The count rate jumped back to 200 cpm in about thirty seconds. In-house Health Physics personnel were alerted, and the llcalth Physics personnel and Operations personnel began to investigate. At approximately 3:45 p.m., the count rate again jumped up to about 2,000 cpm and jumped back down. At 3:50 p.m. the count rate jumped from 200 to 10,000 cpm. At 3:51 the reactor was scrammed and the con-tainment building was evacuated. All personnel were accounted for, and surveyed for contamination. No contamination was found. Unnecessary persennel were released. The Radiation Safety Officer (Mark Pierro) and the Operations Manager (Philip Orlosky) were notified. All pumps were secured, and the operation and icvels of the stack exhaust system were verified to be normal. l l HOTARY Ro AD, BUF F ALO, NEW YORK 14214 TE L.(716)3312826 (FoRMERLY WESTERN NEW YoRh NUCLEAR RESEARCil CENTER, INC.) t
. At 16:27 entered containment wearing full anti c's and Scott air packs. The purpose of the entry was to: - inspect core and controls system (verify safe shutdown). - check the CO2 Pressure on the dry chamber nosepiece and check for bt..Jes. - check the operation of the air monitor (R. Jones is the staff electronics technician), including the insertion of the standard check source. - verify proper flow through the monitor. - recover the building particulate sampling filter. - if the indicated airborne levels were > twice normal--isolate containment (scram ventilation dampers). The entry was accomplished in approximately fifteen minutes. No unusual activity was detected on the air filter. Both personnel came out free of contamination. No unusual conditions were noted in respect to the reactor. The nosepiece CO2 pressure was stable at the normal 12 psi level. The count rate had returned to normal on the air monitors. I decided to allow limited re-entry to containment without protective equipment. The spike in the monitor activity was so short, it was not considered credible. Actual releases take longer to accumulate and dissipate. James Griffin and Kevin Miller proceeded to the neutron deck to check on the status of an autoclave experiment in process. i re-entered to continue investigating the status of the reactor system and the monitor. At approximately 5:15 p.m., two events occurred simultaneously. Bubbling through a weld in the dry chamber nosepiece commenced, and the air monitor again swept upscale. Containment evacuation was repeated. The pressure was let off the nosepiece. Again all personnel were accounted for and surveyed clean. The ventilation dampers were scrammed. The staff convened and discussed the situation at length. The following concepts were developed: 1. The first two (small) releases could in fact be N-16 releases from the nose-piece, the rapid clearance time consistent with the short seven-second half-life of N-16. The levels were small, and posed no threat to personnel. 2. The third release (up to 10,000 cpm) was not credible, and symptomatic of instrument failure. The transient was simply too rapid for a gaseous release. 3. The fourth release was questionable. The personnel did not remain in containment to observe the duration of the release (a conservative and proper choice). Any activity associated with the dry chamber nosepiece leak would have to be A-41 because of the time since shutdown. 4. The slow inleakage into the nosepiece would constitute an unattended positive reactivity insertion, and would produce transient thermal and pressure stresses on the nosepiece. Since the rods were verified as full down, the reactivity effect was considered insignificant. The stresses were similarly considered minor.
4 _3_ It was decided to re-enter to re-supply pressure to the nosepiece and to recover the effluent monitor recorder charts. This was accomplished in approximately six minutes by ~ The recorder tracing recovered indicated multiple and sporadic deflections in count rate (please see Figure II). The building air deflections were mimicked by similar erratic responses in the building particulate monitor. These two instruments share mutual 110V supply and high voltage power supply. It was theorized that a G.M. tube in the building air monitor was drawing down (overloading) the power supply. It was a particularly humid day. It was decided to change out the building air monitor. The primary water monitor (located in the sub-basement) utilizes an identical power supply and ratemeter. This monitor provides no useful information in the absence of primary coolant flow. The primary water monitor was taken out of service to replace the building air monitor. entered containment (wearing SCBA) and installed the alternate monitor. The indicated countrates continued to behave erratically. The system utilizes two G.M. tubes which oy.' rate in parallel. When one of the tubes was disconnected, the countrate dropped and stabilized. After verifying this phenomenon twice, the operators left containment to report to the Operating Committee. After consultation, re-entered to change the suspect G.M. tube. This did not solve the problem. However, it was observed that the cable and connector were defective and wiggling the cable caused the monitor to behave erratically. At this point the operators opened the dampers and exited containment. It was decided to allow the containment to ventilate for a while, since radon decay products accumulate when the dampers are closed. After approximately thirty minutes, the cable was repaired and normal service on the moniter was restored. The primary water monitor was placed back in service. The CO2 Pressure on the nosepiece was balanced to produce a very slight out-leakage of bubbles. The facility has been operated for many years without problems. At 9:52 p.m., the reactor was re-started and normal operations resumed. Releases to the Environment Releases to the environment from the incident are minuscule. The two questionable releases, if actual, would have released N-16 activity at approximate concentra-tions of I x 10-5 and 2 x 10-5 respectively, each for thirty seconds. The average concentration over the one-hour pariod from 3 - 4 p.m. is estimated to be 0.5 x mpc (occupational). This is within technical specifications. It is very likely that there were no unusual releases at all.
4 Exposures to Personnel There were no remarkable or unusual exposures to personnel. Conclusions The reactor staff responded effectively to the event, in compliance with ' applicable procedures. The benefit of previously executed drills was evident. Although the radiation monitor readings were suspect from the beginning, it was conservatively assumed that they were accurate, until definitively proved otherwise. Respectfully submitted, k N W3 Louis'G. Henry, Director May 10, 1985 1
a-l TABLE I l l Evacuees I Name Title Affiliation Mark Adams Senior Reactor Operator NSTF Operations Richard Benson Technician MEA (customer) Janice Cichocki Reactor Operator NSTF Operations l-William Elliott-Supervising Sr. Reactor Operator NSTF Operations
- M. K. Gray Reactor Operator Trainee NSTF Operations James Griffin Senior Health Physicist NSTF Health Physics Craig Miller-Technician MEA (customer)
Kevin Miller Engineer MEA (customer) Norman Misso Technician NSTF - Research Anthony Vargas Senior Reactor Operator NSTF - Operations Carolyn Wall - Senior Technician NSTF - Research .s f-l' k v v-t-s, r, i--w.ra >--n-,, ,,w--,, -v-, -wm u -4 v.w. -+wre, .-n+,e-~ m, ~ ~ - - --- -+e,,* w,~ w - ,n~n~,g,- - -m--,gww~me--r--v-, --o-e
~ TABLE II Recovery and Repair Personnel Name Title Affiliation Alexander Adams "eactor Engineer NSTF James Griffin Senior Health Physicist NSTF Louis Henry Director NSTF Nancy Hutchison Health Physicist NSTF Richard Jones Supervising Sr. Reactor Operator NSTF Philip Orlosky Operations Manager NSTF Mark Pierro Radiation Safety Officer Radiation Protection Services Anthony Vargas Senior Reactor Operator NSTF Kevin Miller Engineer Materials Engineering Associates William O'Brien Buffalo Representative New York State Department of Health
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