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[cdn-nucl-l] FW: Japanese Criticality Accident Summary and Update
> From: Michael C. Baker[SMTP:firstname.lastname@example.org]
> Reply To: email@example.com
> Sent: Tuesday, October 05, 1999 9:40 AM
> To: Multiple recipients of list
> Subject: Fwd: Japanese Criticality Accident Summary and Update
> Here is the latest summary of information about the accident in Japan.
> Mike ... firstname.lastname@example.org
> >From: "Valerie L Putman" <VPUTMAN@inel.gov>
> >To: email@example.com
> >Date: Tue, 5 Oct 1999 01:56:11 -0600
> >Subject: Japanese Criticality Accident Summary and Update
> >My apologies for the delay in sending more information about the 30
> >1999 criticality accident. This message is in three primary parts:
> >I My summary
> >II Dr Komura
> >?s most recent email messages
> >III news article URLs
> >I. ACCIDENT SUMMARY TO DATE by Valerie Putman
> >(see emails and URLs for sources)
> >DISCLAIMER: This summary is necessarily based on news articles, other?s
> >experience with fuel fabrication in the U.S., and email messages from
> >personnel who are not directly involved with the plant, incident
> response, or
> >incident investigation. Available news articles are mostly non-technical
> >often sensationalized and sometimes contradictory, as expected. In
> >there are some questions arising from different nomenclatures and
> >translation problems.
> >For convenience, low enriched uranium (LEU) and intermediate enriched
> >(IEU) are here respectively defined here as less than 10% enriched and
> >A criticality accident occurred at 10:35am (0135 GMT) on September 30,
> >1999. It
> >occurred in a nuclear fuel fabrication plant at the JCO Co. site in
> >Japan. The city is about 140km northeast of Tokyo, in the Ibaraki
> >Public areas are rather close to this plant. However, plant areas
> >little or no shielding because process material is unirradiated. [FYI:
> >is a separate, nuclear fuel reprocessing plant in Tokaimura. It
> >apparently was
> >shutdown after a 1997 fire/explosion accident. If I remember correctly,
> >was a chemical or industrial accident but it released radioactive
> material. I
> >speculate BBC video of a building with a hole in its roof is actually
> >footage of this other plant, taken during or after that earlier
> >The plant had no criticality accident response plans because it was
> >?critical fission chain reactions could not occur. [More probably,
> "Emergency planning was not required because management and authorities
> assumed a criticality accident was not credible, if an appropriate
> criticality safety program was implemented."]
> >This fabrication plant converts UF6 gas to UO2 powder. It primarily
> >LEU (5%) fuel for PWRs. However, this time the product was 18.8%
> enriched fuel for JOYU, a fast-breeder research reactor. News articles
> indicate IEU processing was not new but it was apparently last conducted
> three years ago.
> >Operational limits might be based on the highest enrichment allowed, but
> >more likely changed when needed to accommodate the LEU and IEU
> >Apparently this was either the first campaign, or first campaign with
> IEU, for
> >two operators. In addition, the third operator had only a few months
> >experience with the subject operation, with handling IEU, or both.
> >The subject operation apparently was a precipitation process involving
> uranium oxide and uranyl nitrate. [One report indicates the material is
> UF6 but most others specify uranium, uranium oxide, and or uranium and
> nitric acid.]
> >Apparently uranyl nitrate is added in batches to a sedimentation
> >(precipitation?) tank. Emails indicate the tank was a vertical cylinder,
> >with a 50cm diameter, dished bottom, 3mm stainless steel walls, and an
> approximate 2.5cm-thick-water cooling jacket around the sides and bottom.
> >A regulator-approved manual controls plant operations. For this
> >material must first be weighed and added to a separate, small dissolution
> >Apparently material is uranium oxide and nitric acid, but it might be
> >concentrated uranyl nitrate. Resultant solution is then transferred to
> >sedimentation vessel via plant piping. The batch size is operationally
> >limited to a maximum 2.3 or 2.4kg U or, less likely, 235U.
> >However, two to five years ago JCO officials approved a manual change
> without regulator concurrence or notification. This change significantly
> accelerates the process (3 hours vs. 30 minutes, if a churning device
> [stirrer?] is used in the sedimentation tank). It allows operators to use
> steel buckets and funnels to add materials directly to the sedimentation
> tank. Some reports
> >indicate the buckets are 50L mop buckets, considerably larger than the
> aforementioned dissolution tank. One official indicated the change would
> not have been approved because uranium oxide, nitric acid, and stainless
> steel react to produce a toxic gas [can anybody tell me what the reaction
> and products are?].
> >On Wednesday, operators poured about 9.2kg uranium from four buckets into
> the sedimentation tank. On Thursday, operators added about 6.9kg uranium
> from three buckets, triggering the critical excursion. The uranium was
> "condensed" which I think refers to uranium oxide powder, although it
> might refer to highly concentrated uranyl nitrate. The resultant
> solution, or reflected slurry, went "flash critical" [possibly prompt
> critical?]. One email indicates the
> >critical material was approximately 370g/L uranium with, possibly,
> 1mole/L nitric acid.
> >Operators saw a blue flash. Reportedly they felt sick immediately. [I'd
> >sick that quickly just knowing what the blue flash means, whether or not
> >physical symptoms were evident that quickly.] Presumably everybody in
> >room left as quickly as they could; reports do not indicate if radiation
> >were installed or activated. 35-year-old Hisashi Ouchi received 17Sv,
> 39-year-old Masato Shinohara received 10Sv, and 55- or 54-year-old Yutaka
> Yokokawa received some unspecified lower radiation dose. [Based on doses
> reported for other accidents, I assume Ouchi and Shinohara were next to or
> leaning over the tank, and Yokokawa was a few feet away from the vessel.]
> These three operators were
> >hospitalized and, as of Oct. 4th, all three were alive. In fact,
> >apparently was well enough to answer investigator questions by Oct. 2nd.
> >However, doctors planned to give Ouchi a bone marrow transplant, at last
> >report (Oct. 4th).
> >News reports indicate an additional 37 or 38 people also received some
> >non-trivial radiation doses, including three fireman who responded, five
> >nearby residents, and two employees of a nearby golf-course. [Just
> reinforces what I'd always heard: Japan is densely populated, with little
> if any space between industrial/nuclear/chemical plants and the public.]
> Reports either do not quantify, or provide wildly discrepant indications
> of, radiation levels. Many articles report radiation levels anywhere from
> 1000 to 17000 times above normal levels. One embassy official told INEEL
> personnel that responders measured a fairly steady 0.84mSv/hr dose rate at
> the facility boundary for several hours after the accident, and further
> indicated that fission neutrons were detected during that time. Until the
> system was safely subcritical, about 160 people within a 350m radius were
> evacuated, and people between 350m and 10km were advised to stay inside
> (with doors and windows closed).
> >Official notifications were reportedly slow but news articles did not
> >most elapsed times. City officials were apparently told almost an hour
> >the first critical excursion. Radiological responders were apparently
> >from the plant and presumably activated immediately. Other in-field and
> >responders were apparently from the civil police, civil firefighters, and
> >army. Naturally they weren't activated until official notifications were
> made. One or more Japanese authorities requested US experiential
> information but it seems doubtful it was very useful in shutting down the
> >One would expect the system to oscillate (or pulse) between super- and
> >sub-critical states, or to shut itself down quickly. However, the system
> >apparently settled into a quasi-steady-state for almost 20 hours.
> >Tokyo Electric Power Company rushed some 880 lbs of borated material
> [boric acid?] to the JCO plant. However, responders could not use it
> right away because they had no readily apparent means of remotely adding
> the neutron absorber to the tank.
> >Dr. Komuro wrote: It took about 3 hours to drain cooling water from a
> >jacket around the tank. At 02:35 Oct. 1st, two workers with radiation
> >protection coveralls took some pictures of a cooling-water-drain-valve
> outside the building in which the nuclear criticality accident occurred.
> The area where the valve was highly contaminated [I think he means highly
> radioactive]. Although they stayed in the area only 3 minutes, one of
> them received 11.92mSv gamma and 91.2mSv neutron. At 03:00 another two
> workers went to a pump yard(?) and confirmed a
> cooling-water-circulation-pump(s) was working well. At 03:22 another two
> workers opened the valve. However responders could not confirm that water
> was successfully discharged from the water jacket. Finally other workers
> cut a drain pipe outside at the valves up-stream side, and injected gas.
> At 06:00 responders confirmed cooling water was exhausted. The tank was
> finally subcritical. 18 workers total were involved in draining the water
> >Apparently responders added boron to the system. Officials declared the
> >system safely subcritical at 9:20am Oct. 1st. I do not know what
> prompted premature news reports that the reaction had terminated at
> various times after 6:30pm Sept. 30th.
> >Fission yields are not specified for any pulse or for the reaction
> >After the first pulse, the maximum neutron dose reported was 4.5mSv/hr,
> >detector location with respect to the tank is not indicated.
> >Apparently regulators declared this a Level 4 incident using the IAEA
> >guidelines. Their basis was radiation exposures to two operators and to
> >off-facility people. The building suffered no mechanical damage but
> >filters did not trap fission products. Essentially all fission products
> were released to the atmosphere. Officials warned people they should not
> eat produce or drink milk from the area until testing was complete.
> [However, I'm not certain why they thought this accident would release
> enough to be harmful.]
> >Accident investigation for response decisions began immediately. Further
> >investigation apparently began the afternoon of October 1st. JCO
> conducted an in-house investigation and apparently police are conducting
> much of the
> >official investigation. One news article indicated police raided JCO
> offices [is this anything like the USA FBI raiding DOE's Rocky Flats site
> years ago?].
> >MISCELLANEOUS consequences and reactions:
> >Tokaimura resident attitudes range from calm to angry about nuclear
> >safety, but few are concerned about long-term radiological effects
> >Greenpeace is sending people to survey Tokaimura
> >Japanese, USA, and UK programs will be reviewed in light of the accident
> >If USA experience is indicative, the JCO plant's entire safety basis will
> >scrutinized and reworked
> >Stock in JCO's parent company is apparently dropping.
> >Japan might review its nuclear policy but dramatic changes are doubtful
> >US President Clinton threatened (or did) veto a bill regarding Yucca
> > and nuclear waste
> >II. Dr. KOMURA's 2nd, 3rd and 4th EMAIL MESSAGES
> > >From Yuichi Komuro <firstname.lastname@example.org> on 10/02/99
> > 01:00am GMT
> > Subject: 3rd information on the accident in Japan
> >The source of the following information is "Mainichi Shinbun" news paper
> >(in Japanese) of October 1, evening version.
> > It took about 3 hours to drain cooling water from a water jacket around
> >solution tank. At 02:35 a.m. 1st of October, two workers with radiation
> >protection coveralls took some pictures of a cooling-water-drain-valve
> >outside the building in which the nuclear criticality accident occurred.
> >The area where the valve was highly contaminated. Although they stayed in
> >the area only 3 minutes, one of them received 11.92 mSv of Gamma-ray and
> >91.2 mSv of neutron. At 03:00 a.m. other two workers went to a pump yard
> >(?) and they confirmed that a cooling-water-circulation-pums(s) was
> >well. At 03:22 a.m. other two workers opened the valve. However it
> >not be confirmed that water was successfully discharged from the water
> >jacket. Finally other workers cut a drain pipe outside at the upper
> >side of the valve and injected gas to assist water discharge. At 06:00
> >a.m. it was confirmed cooling water was exhausted and then the tank
> >subcritical state. This water-drain was performed by 18 workers in
> >I hope you find this information useful.
> >Sincerely yours,
> >Yuichi Komuro
> >Department of Research Reactor
> >Japan Atomic Energy Research Institute
> >Tokai-mura, Naka-gun,
> >Ibaraki-ken, 319-1195
> >e-mail : email@example.com
> >telephone :+81-29-282-5823 (new)
> >fax : +81-29-282-6763 (new)
> > >From Yuichi Komuro <firstname.lastname@example.org> on 10/03/99
> > 02:54am GMT
> >Subject: 4th information
> >Sorry, I have no detailed technical information such as uranium chemical
> >composition, uranium concentration and tank geometry, since I am not a
> >member of advisory experts team. In the near future, an official report
> >concerning the Japan's worst nuclear accident will be issued.
> >1) Two of three workers of JCO received 17Sv and 10 Sv, respectively.
> >2) Information shown below is from "The Daily Yomiuri On-line" of 3rd of
> >JCO admits procedures violated
> > N-facilities law
> >Yomiuri Shimbun
> >MITO -- JCO Co., which operates the uranium-processing
> >facility in Tokaimura, Ibaraki Prefecture, where Japan's
> >worst nuclear accident occurred Thursday, revealed
> >Saturday it had followed an internal procedural manual for
> >processing nuclear fuel that did not meet legal
> > requirements.
> >The company also acknowledged it had handled a solution
> >of uranium oxide and nitric acid on Wednesday using the
> >same method employed on the day of the accident.
> >Managers of the facility allegedly gave their tacit approval
> >for the nonstandard processing of uranium.
> >At a press conference held at Ibaraki prefectural
> >government offices, JCO said the procedural manual
> >stipulated that 10-liter stainless containers be used when
> > mixing uranium oxide into a nitric acid solution.
> >However, the use of such containers is not approved by
> >the law governing nuclear reactors and facilities.
> > JCO's Tokaimura office compiled a procedural manual in
> > line with the law in 1989, but revised the manual in
> >October 1997 to allow the use of stainless containers.
> >The company, however, did not submit the necessary
> >documentation on the proposed revisions to the Science
> >and Technology Agency for approval and therefore the
> >procedure was not screened by the agency.
> > "Stainless containers are easy to use, and workers had
> >been using them for four to five years before the revisions
> >to the manual were made," Hiroyuki Ogawa, a JCO official,
> >said at the press conference. "The revisions were
> >approved by the production manager at the Tokaimura
> > office."
> > He added, "When uranium oxide is mixed with nitric acid in
> >a stainless container, toxic gas will be produced and
> >create safety problems. Even if the company filed an
> >application for revisions (to the manual), it would not have
> > been approved."
> >JCO also said four stainless containers of uranium oxide
> >solution and nitric acid were poured into the sedimentation
> >tank on Wednesday. The solution contained 9.2 kilograms
> >of uranium.
> > On Thursday, three containers of the solution containing
> >6.9 kilograms of uranium were added to the tank,
> >triggering a nuclear fission chain reaction.
> >Ogawa said the company was still investigating why the
> >workers bypassed some of the procedures and poured the
> >solution into the sedimentation tank.
> > "To balance the concentration of uranium oxide in the nitric
> >acid solution takes three hours if the stipulated procedure
> >is followed and the solution is put through a dissolution
> >tank," Ogawa said. "It takes about 30 minutes if the
> >sedimentation tank with the churning device is used."
> > Ibaraki prefectural police, meanwhile, questioned Yutaka
> >Yokokawa, 54, one of the three workers exposed to
> > radiation in the accident. Yokokawa's symptoms are
> >relatively light.
> >"We have (previously) processed more uranium than
> >regulations permitted for one operation," Yokokawa was quoted as saying
> >police. "We followed the manual
> >unilaterally set by the company."
> >Yokokawa told police that the workers skipped some of the
> >procedures because "they were in a hurry."
> >Copyright 1999 The Yomiuri Shimbun
> >Sincerely yours,
> >Yuichi Komuro
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