Nuclear Energy: Consequences of Explosion of Hanford's Single-Shell Tanks Are Understated

Published by the Government Accountability Office on 1990-10-10.

Below is a raw (and likely hideous) rendition of the original report. (PDF)

                     ~Subcommittee, Committee on
                     Government Operations, House of

                     NUCLEAR ENERGY
                     Explosion of Hanford’s
                     Single-Shell Tanks Are


GAO/ tI(:tm-Y1-:~4
                       United States
,! GAO
                       General Accounting Office
                       Washington, D.C. 20648

                       Resources, Community, and
                       Economic Development Division


                       October lo,1990

                       The Honorable Mike Synar
                       Chairman, Environment, Energy,
                       and Natural Resources Subcommittee
                       Committee on Government Operations
                       House of Representatives

                       Dear Mr. Chairman:

                       On December 8,1989, you asked us to review the Department of
                       Energy’s (DOE) efforts to identify a solution for disposing of the high-
                       level waste stored in underground tanks at its Hanford Site near Rich-
                       land, Washington. As part of this review, we evaluated the work that
                       has been done by DOE Richland and its contractors to understand and
                       resolve questions concerning the stability of ferrocyanide-a     potentially
                       explosive material found in significant concentrations in 22 of the 149
                       single-shell storage tanks. Because our evaluation raised serious ques-
                       tions about the potential consequences of such an explosion, this report
                       addresses the potential for an explosion. Our report on the remainder of
                       your request will be issued in the near future.

                       The consequences of an explosion in an underground waste storage tank
    Results in Brief   containing ferrocyanide would be more severe than reported by DOE in
                       the 1987 Hanford Site environmental impact statement (EIS). The EIS
                       stated that an explosion in a tank containing ferrocyanide would create
                       enough energy to release radioactive material to the atmosphere
                       through ventilation openings (filters), exposing persons off-site to radia-
                       tion doses equivalent to what they would receive from natural and man-
                       made radiation sources.’

                       Although studies performed by DOE as early as 1984 and more recently
                       by other experts, including the Defense Nuclear Facilities Safety Board,
                       indicate that the probability of a ferrocyanide-caused explosion is low,
                       this conclusion is based on limited information on the conditions of the
                       waste in the tanks containing ferrocyanide. Our review of the work per-
                       formed by DOE contractors indicates that, although the probability of an
                       explosion may in fact be low, not enough is known about the waste in
                       the single-shell tanks to definitely rule out the possibility of a sponta-
                       neous explosion.

                       *The average U.S. citizen receives About 0.38 rem per year from natural and man-made sources.

                       Page 1                                                         GAO/RCED-91-94     Nuclear   Energy
             Is241479                                                                      ,

             If an explosion did occur, our review indicates that it would be a major
             accident, with potentially more damaging effects than those described in
             the Hanford EIS, including contamination of large areas within and pos-
             sibly beyond the Hanford Site boundaries, in addition to the human
             health effects. The force of this explosion would blow a large hole in the
             tank top and its overburden of earth. The radioactive material ejected
             from the tank could expose persons to radiation levels higher than
             reported in the EIS. Because limited data are available, the exact expo-
             sure levels are uncertain. The potential does exist, however, that, if an
             explosion occurs, off-site radiation exposure could rise to levels with
             potentially significant radiation-induced cancer consequences.

             As a result of our discussions with DOE Richland, the Director, DOE Office
             of Environmental Restoration and Waste Management, appointed a team
             of independent DOE experts (referred to as the “Ad Hoc Task Force”) to
             review our calculations of the potential radiation exposure. This Task
             Force, which reported its findings on September 20, 1990, agreed with
             our assessment that the respirable fraction of radioactive particles pro-
             duced by the explosion would be higher than that used in the 1987 EIS,
             but stated that additional studies are needed to determine the potential
             radiation dose. The Task Force made numerous recommendations to DOE
             for additional studies to develop more precise information for resolving
             the ferrocyanide issue.

             The Hanford Site, located on the Columbia River in southeastern Wash-
Background   ington State, is operated by the Westinghouse Hanford Company for
             DOE. Constructed in 1943, this major DOE defense facility, among other
             activities, reprocesses spent reactor fuel to recover the plutonium. This
             process produces a large volume of highly radioactive, heat-producing
             liquid wastes. Underground waste storage tanks were built to tempo-
             rarily store this waste until a more permanent disposal solution could be

             The first underground storage tanks consisted of a carbon-steel liner
             surrounded by reinforced concrete. Later, double-shell tanks-that    is, a
             carbon-steel tank within a carbon-steel liner surrounded by reinforced
             concrete-were built. Over the years, 149 single-shell and 28 double-
             shell storage tanks, located within 12 to 22 miles of the Hanford bound-
             aries, have been constructed. To control corrosion of the carbon steel
             tanks, sodium hydroxide is used to neutralize the acidic liquid wastes. A
             major waste component produced as a result of this neutralization is
             sodium nitrate.

             Page 2                                          GAO/&cED-91-24   Nuclear   Energy


    Over the years, DOE devised various waste reduction procedures to mini-
    mize the number of storage tanks required. One of these procedures
    involved precipitating out the heat-producing, hazardous, and relatively
    long-lived radioactive isotope cesium-137 so that the remaining liquid
    could be pumped out of the tanks and sent to underground seepage
    structures. Prom 1964 to 1967, DOE used sodium and potassium ferrocy-
    anide and nickel sulfate to precipitate out the cesium-137. According to
    DOE, this process caused various ferrocyanide precipitates to settle to
    the bottom of the tank, including cesium nickel ferrocyanide. The ferro-
    cyanide precipitates are potentially hazardous because of the explosion
    danger, especially those containing the heat-producing cesium nickel

    While DOE has documented some concern about ferrocyanide reactions in
    earlier reports, in 1983, its concern was renewed by studies assessing
    waste tank disposal options. As a result, DOE’S Pacific Northwest Labo-
    ratory (PNL) carried out a preliminary literature evaluation of the poten-
    tial hazard involved. The PNL 1984 report, summarizing the results of
    this evaluation, pointed out that (1) up to 140 metric tons (154 tons) of
    cyanide are contained in at least 14 single-shell tanks2 with as much as
    30 metric tons in 1 tank and 16 metric tons in another and (2) at high
    temperature, ferrocyanides could react with nitrates and release large
    amounts of heat and, if the reaction is very rapid, the result will be an
    explosion? The report further presented a worse-case scenario, which it
    characterized as highly improbable, in which ferrocyanide reacting with
    sodium nitrate would produce an explosion equivalent to 36 tons of

    In DOE’S 1987 environmental impact statement (EIS) for the Hanford
    high-level waste, DOE evaluated the environmental, safety, and health
    effects of various high-level waste disposal options4 As part of this
    evaluation, DOE considered a ferrocyanide explosion to be an Upper
    Bound, or worst case, accident during disposal of the Hanford high-level
    waste. The EIS stated that this worst case accident would have “suffi-
    cient energy to breach the filters [ventilation openings] on the tank and
    release radionuclides as aerosols directly to the atmosphere.” Although

    2As of September 1990, DOE had identified 22 single-shell tanks containing significant concentrations
    of ferrocyanlde.

    3L.L. Burger, Complexant Stability Investigation Task I-Ferrocysnide   Solids, Pacific Northwest Lab-
    oratory, PNL%441 (Nov. 1984, released Aug. 1989).
              of Hanford Defense High-Level, Transuranlc and Tank Wastes, Department of Energy,
              0113 (Hanford Site Richland, Wash.: Dec. 1987).

    Page 3                                                           GAO/RCED91-34       Nuclear   Energy
                       B&l479                                                                                          I

                       the EIS did not address the on-site consequences of a ferrocyanide explo-
                       sion, it did report that persons off-site would be exposed to radiation
                       doses approximately equivalent to natural and man-made radiation

                       Although DOE has concluded that an explosion in a tank containing fer-
DOE Has Insufficient   rocyanide is highly unlikely, this conclusion is based on many uncertain-
Information for        ties, including the composition of the waste material stored in the tanks.
Judging the            According to DOE, little is known about the precise contents of the tanks
                       containing ferrocyanide. During the time that ferrocyanide was used,
Probability of a       waste streams to and from the tanks were sampled and analyzed for
Ferrocyanide           limited constituents for purposes considered important at the time. But
Explosion              the available historical records are not adequate for determining the
                       concentrations of the various waste constituents. Thus, it is difficult to
                       estimate precisely the character of the wastes contained in the tanks
                       without extensively sampling tank contents.

                       PNL'S November 1984 report, which was not publicly released until the
                       summer of 1989, concluded that not enough was known about the condi-
                       tions in the tanks to state that the hazard of a potentially violent reac-
                       tion did not exist. The report described many unknown circumstances
                       that could affect the stability of the ferrocyanide precipitates and made
                       several recommendations to resolve the uncertainties concerning tank
                       temperatures and the amounts and concentrations of ferrocyanide avail-
                       able in the tanks. (App. I lists each of the recommendations and the
                       actions taken to respond to them.)

                       In response to concerns initially surfaced in the 1984 DOE report, West-
                       inghouse Hanford Company analyzed available information for those
                       tanks suspected of containing ferrocyanide. A Westinghouse internal
                       memorandum, dated March 2, 1989, reported Westinghouse’s evaluation
                       of the tank conditions that might affect ferrocyanide nitrate reactions
                       and identified those tanks believed to have the highest potential for a
                       ferrocyanide explosion. On the basis of studies performed to date, DOE
                       believes that an explosion in a ferrocyanide tank is highly unlikely.

                       Our review of the work performed by the Westinghouse Hanford Com-
                       pany and PNL indicates that, although the probability of an explosion
                       may in fact be low, not enough is known about the waste in the single-

                       ‘Until recently, DOE did not consider, in an EIS, the on-site consequencesin assessingthe health and
                       safety impacts of it.9 actions.

                       Page 4                                                           GAO/BCEDBl-84      Nuclear   Energy
shell tanks to rule out the possibility of a spontaneous explosion. Specif-
ically, the work does not adequately resolve questions concerning two of
the key factors affecting the stability of the ferrocyanide precipitates-
the temperature of the waste and the identity, amounts, geometry, and
concentrations of the ferrocyanide precipitates.

The 1989 Westinghouse memorandum compared the temperatures mea-
sured in the tanks containing ferrocyanide with the temperatures
required to initiate a ferrocyanide reaction and noted a large safety
margin between the two temperatures. (According to DOE'S independent
team of experts, the highest temperature measured in a tank containing
ferrocyanide was 1350 Fahrenheit (F), whereas, the lowest temperature
at which a reaction has been observed in the laboratory is 4460 F.) In
addition, the Westinghouse memorandum noted that concerns about
temperature increases after all of the pumpable liquid had been
removed were not supported by experience to date because there have
been no apparent subsequent temperature increases in the ferrocyanide
tanks that have been pumped.

We question the temperatures used to support this argument because
the temperatures are measured only along one vertical line, sometimes
near the edge, in each tank. Consequently, there are no records of tem-
peratures at other points in tanks that are 75 feet in diameter and 30
feet deep. Therefore, the cyanides, which contain the heat-producing
isotope cesium-137 may be generating local hot spots elsewhere in the
tank away from the thermocouple string. Further, although hot spots
may not have developed yet, they could appear, as moisture in the tanks
continues to evaporate and the ferrocyanide material becomes dry. If, in
fact, the situation is changing with time at some localized hot spots in
the tanks, an explosion may still be possible even after all these years.

Westinghouse officials told us that additional temperature monitors will
be installed in several locations within at least one tank containing fer-
rocyanide to determine if any localized hot spots exist. According to
these officials, the results of this effort will then be evaluated to deter-
mine whether or not additional temperature probes need to be installed
in other tanks containing ferrocyanide.

With respect to the second key factor, DOE'S measurements of the explo-
sive properties of the ferrocyanides have been limited almost entirely to
cesium nickel ferrocyanide. However, our calculations indicate that only
a tiny fraction of the ferrocyanide material in the tanks is cesium nickel
ferrocyanide. Almost all is an unknown combination of other metal ions

Page 6                                            GAO/RCED-91-34   Nuclear   Energy
                      B-241479                                                                       ,

                      with the ferrocyanide, The temperatures which may cause an explosion
                      of these materials may be different from those of the cesium nickel fer-
                      rocyanide, In fact, some limited experimental work by PNL in 1988 using
                      potassium ferrocyanide indicated that such differences do exist.

                      Westinghouse representatives told us that they have discussed inter-
                      nally the need to examine how other materials might combine with fer-
                      rocyanide and how that might affect transition temperatures. They said
                      that studies which will provide answers to those questions are planned
                      but not yet scheduled. They explained that DOE'S Los Alamos National
                      Laboratory is conducting large-scale explosion testing for PNL to deter-
                      mine the explosive behavior of a large sample of cesium nickel ferrocya-
                      nide and nitrate/nitrite.

                      During the past year, the Defense Nuclear Facilities Safety Board, DOE'S
                      Advisory Committee on Nuclear Facility Safety, the State of Washington
                      Department of Ecology, and others have reviewed the storage situation
                      at the Hanford Site, concentrating primarily on the probability of an
                      explosion. Although each group concluded that the probability of an
                      explosion in any tank containing ferrocyanide was low, each identified
                      problems similar to ours with respect to the lack of precise information
                      about the waste material in the single-shell tanks and recommended that
                      additional studies be undertaken.

                      In response to recommendations made by the Safety Board on March 27,
                      1990, DOE developed a plan to study possible chemical reactions that
                      could cause heat generation in the single-shell tanks and to improve its
                      temperature measurements in those tanks containing ferrocyanide. In
                      addition, DOE plans to test the radiation stability of ferrocyanide precipi-
                      tates and the energetics of ferrocyanide reactions beginning in fiscal
                      year 1991. Following these actions, DOE will determine the need for addi-
                      tional action as recommended by the Safety Board.

                      The Hanford EIS stated that an explosion in a tank containing ferrocya-
Potential             nide would create sufficient energy to release radioactive material to the
Consequencesof a      atmosphere through ventilation openings (filters), exposing persons off-
Ferrocyanide          site to radiation doses from all exposure pathways (air, soil, water, and
                      food) approximately equivalent to what they would receive from nat-
Explosion Have Been   ural and man-made radiation sources. However, this conclusion was
          ”           based on the assumption that the cesium would be evenly distributed
                      throughout the tank waste.

                      Page6                                            GAO/IUXD-91-34NuclearEuergy
.   Ez41479

    We believe, however, that the cesium is more likely to be concentrated in
    the explosive material (that is, the ferrocyanide precipitates). We
    believe this because the ferrocyanide was added to the waste to bind
    with and precipitate out the cesium-137. If the cesium-137 is concen-
    trated in the explosive material, our calculations indicate that a ferrocy-
    anide-caused explosion would result in a higher level of radioactivity in
    the small radioactive particles being dispersed, increasing the dose that
    people might inhale to levels higher than the EIS indicated. Further, the
    force of this explosion would blow a large hole in the tank top and its
    overburden of earth. To the extent that the ferrocyanide is located
    under other waste in the tank, much of the waste would be blown out of
    the tank along with the gaseous products of the reaction. Among these
    products would be radioactive strontium-90 and cesium-137. (Strontium-
    90 is another highly radioactive element contained in the tanks.) Such
    an explosion would be a major accident, with potentially more damaging
    effects than those described in the Hanford EIS, including contamination
    of large areas within and possibly beyond the Hanford Site boundaries,
    in addition to the human health effects.

    Because limited data are available, no one knows how much of the
    cesium-137 would be ejected as respirable particles. However, the
    greater the concentration of cesium-137 in the explosive material, the
    more likely it will be that a greater fraction will be in the form of respir-
    able particles. For illustrative purposes, if one were to assume that
    about 6 percent of the concentrated cesium-137 becomes airborne as
    respirable particles, our calculations indicate that an explosion could
    produce radiation levels significantly higher than natural radiation
    sources. Off-site exposure from cesium-137 and strontium-90, for
    example, could be as high as, but likely will be less than, 7.3 rems6 For
    perspective, at the highest potentially estimated dose level of 7.3 rems,
    tables prepared by the National Research Council would indicate that
    approximately 1 additional person out of every 160 exposed to this dose
    could die from radiation-induced cancer over an extended period of

    It should be noted that our off-site exposure calculation does not con-
    sider exposure pathways other than the inhalation pathway. For

    @lkii represents the equivalent whole-body 70-year commltted dose (that is, the dose resulting from
    inhallng radioactive particles which deposit radioactivity in the body that continues to emit radiation
    to the body for 70 years).

    ‘Derived from table 42, Health Effects of Exposure to Low Levels of Ionizing Radiation. BEIR V.
    Committee on the Biological Effects of Ionizing Radiations, Board on Radiation Effects, Research
    Commission on Life Sciences,National Research Council, pp. 172 and 173.

    Page 7                                                             GAOmCED-91-34       Nuclear   Energy

                   R-241479                                                                      *

                   example, these figures do not include the external dose that someone
                   would receive from the passing radioactive cloud, the dose delivered by
                   the radioactivity after it is deposited on the ground, or the dose ingested
                   through food and liquids.

                   Westinghouse Hanford and PNL officials agreed with our determination
                   that the force of such an explosion would blow a large hole in the tank
                   top and the earth overburden and our determination that the radiation
                   doses may be higher than those presented in the 1987 Hanford EIS. They
                   believe, however, that additional definitive, relevant experimental data
                   must be obtained before accurate values for the radiation doses can be

                   As a result of our discussion with DOE Richland on August 22, 1990, the
Agency Actions     Director, DOE Office of Environmental Restoration and Waste Manage-
                   ment, appointed a team of independent DOE experts on August 24,1990,
                   to review our calculations of the potential radiation exposure. This DOE
                   Ad Hoc Task Force, which reported its findings on September 20,1990,
                   agreed with us that the cesium would be concentrated in the explosive
                   material and that the respirable fraction of radioactive particles pro-
                   duced by the explosion would be higher than that used in the 1987 EIS.
                   However, the Task Force commented that no data are available to accu-
                   rately quantify the potential inhalation dose and that additional factors,
                   such as how much of the ferrocyanide would participate in the explo-
                   sion, need to be addressed to determine the dose.

                   The Ad Hoc Task Force report, dated September 20, 1990, recommended
                   to DOE that additional studies be performed to provide information on
                   the following:

                 . The potential for a ferrocyanide explosion.
                 . The conditions in the tanks most likely to initiate such an explosion.
                 . The potential consequences of such an accident. (The specific recom-
                   mendations can be found in app. 11.)

                   On September 26, 1990, the DOE High-Level Radioactive Waste (HLW)
                   Tanks Task Force, the HLW Tanks Advisory Panel, and the Westinghouse
                   Ferrocyanide Response Task Team considered the Ad Hoc Task Force
                   recommendations in formulating a program to address the ferrocyanide

                   Page8                                            GAO/RCED-9134NuclearEnergy

 .                    0241479

                      issue.6 On October 3, 1990, the Director, DOE Office of Environmental
                      Restoration and Waste Management, requested that the Richland Opera-
                      tions Office submit an integrated conceptual plan to address the ferrocy-
                      anide issues by October 16, 1990. The DOE Richland Operations Office
                      was also requested to (1) carefully review the on-going and planned pro-
                      grams to address high-level waste tanks’ safety basis and issues and
                      make necessary revisions to be consistent with the high priority
                      assigned to tank safety and (2) identify how the Ad Hoc Task Force
                      recommendations have been incorporated in DOE Richland’s program

                      The consequences of an explosion in an underground waste storage tank
Conclusions           containing ferrocyanide would be more severe than reported by DOE in
                      the 1987 Hanford EIS. Because so little is known about the waste in the
                      ferrocyanide tanks,’ the probability of such an explosion is unknown.

                      DQE’S planned course of action, as identified in its response to the
                      Defense Nuclear Facilities Safety Board, if carried out, would provide
                      much needed data. However, the additional studies recommended by
                      DOE’S Ad Hoc Task Force should be implemented by DOE Richland Opera-
                      tions Office so that sufficient information can become available to deter-
                      mine more precisely the probability of a ferrocyanide explosion and the
                      potential consequences of such an event.

                      We recommend that the Secretary of Energy direct the DOE Richland
Recommendations       Operations Office to implement the recommendations made by the DOE
                      Ad Hoc Task Force on September 20,199O.

                      As requested by your office, we did not obtain official DOE comments on
Agency Comments and   this report. However, we discussed the facts presented in the report and
Our Response          our detailed calculations with DOE program and contractor officials. DOE
                      generally concurred with the facts. An independent task force estab-
                      lished by DOE also agreed with our analyses that the potential conse-
                      quences of a ferrocyanide explosion would be greater than reported in

                      sAccording to DOE, the High-Level Waste Tank Task Force, established on Sept. 6,1990, is to identify
                      and address safety issues related to high-level waste tanks at all DOE sites, whereas, the Westing-
                      house Ferrocysnide ResponseTask Team will only address issues relating to Hanford ferrocyanide
                      tanks. The High-Level Waste Tanks Advisory Panel will advise DOE on issues related to safe and
                      efficient operations of high-level waste tanks at DOE facilities.

                      Page 9                                                           GAO/RCED91-34      Nuclear   Energy

the Hanford EIS and recommended additional studies to resolve the cur-
rent uncertainties.

We performed our review between February and September 1990 in
accordance with generally accepted government auditing standards.
Technical assistance in performing this review was provided by Dr.
George W. Hinman, DSc. Dr. Hinman, currently Director, Office of
Applied Energy Studies at Washington State University, has worked 40
years in the nuclear energy field in industry, government, and academia.

To assess the potential threat of a ferrocyanide explosion in the tanks,
Dr. Hinman reviewed available studies concerning various aspects of the
ferrocyanide situation and made independent calculations of the pos-
sible consequences of a ferrocyanide-caused explosion. To verify the
accuracy of his work, his calculations were reviewed by Westinghouse
Hanford, PNL, and an independent task force established by the Director,
DOE Office of Environmental Restoration and Waste Management.

We also discussed our work with Do&Richland and Washington, D.C.,
officials. However, as you requested, we did not obtain formal agency
comments on this report.

As arranged with your office, unless you publicly announce its contents
earlier, we plan no further distribution of this report until 30 days from
the date of this letter. At that time, we will provide copies to DOE and
other interested parties upon request.

This report was prepared under the direction of Victor S. Rezendes,
Director of Energy Issues (202) 276-1441. Other contributors to this
report are listed in appendix III.

J. Dexter Peach
Assistant Comptroller General

Page 10                                         GAO/WED-91-34   Nuclear   Energy
Page 11   GAO/RCELk91-34   Nuclear   Energy


Appendix I                                                                                            14
Pacific Northwest
Evaluation of
Appendix II                                                                                           18
Report of the DOE Ad
Hoc Task Force
Appendix III                                                                                          22
Major Contributors to
This Report


                        DOE       Department of Energy
                        EIS       Environmental Impact Statement
                        GAO       General Accounting Office
                        HLW       High-Level Waste
                        PNL       Pacific Northwest Laboratories

                        Page 12                                    GAO/RCED-91-84   Nuclear       Energy
Page 13   GAO/liCJD9l-34   Nuclear   Energy
Appendix I

Pacific Northwest Laboratories’ Evaluation of -
Potential Ferrocytide Explosion

                In 1984, Pacific Northwest Laboratories (PNL) carried out a preliminary
                evaluation of the potential hazard associated with ferrocyanides com-
                bined with nitrates in the single-shell storage tanks. The report, entitled
                Complexant Stability Investigation Task I-Ferrocyanide       Solids by L.L.
                Burger, ~~~6441, was prepared in November 1984 but was not released
                until the summer.of 1989.The following summarizes the recommenda-
                tions made in that report and the work that has been done to date.

                1. “Obtain and analyze the available information on tank histories for
                those tanks known to have held Fe(CN),4- in large quantities at one

                An internal Westinghouse Hanford Company memorandum, dated
                March 2,1989, addressed the ferrocyanide tank data. This memo-
                randum reported Westinghouse’s evaluation of the tank conditions that
                might affect ferrocyanide-nitrate reactions, and identified those tanks
                believed to have the highest potential for a ferrocyanide reaction.

                The report identified the factors that might affect a ferrocyanide reac-
                tion as the temperature of the solids; the amounts and concentrations of
                ferrocyanide and oxidants (nitrates/nitrites); and the presence of cata-
                lysts, diluents, and moisture.

                2. “Conduct radiolysis tests under simulated tank conditions to deter-
                mine the rate of disappearance of CN- and to identify the radiolysis
                products. The radiolysis tests should be conducted both with aqueous
                phase present and on settled sludges alone.”

                A study of this kind was issued in 1986. A preparation of cesium nickel
                ferrocyanide was irradiated under a sodium nitrate solution to 2.1~10+~
                rad using Cobalt-60 gamma ray radiation. There was negligible decom-
                position of the cesium nickel ferrocyanide at least in the form of soluble

                The experimenters tentatively concluded that little or no degradation of
                the cesium nickel ferrocyanide had occurred as a result of radiolysis.
                They recommended that further analyses be done on the irradiated
                material to be sure there were no insoluble reaction products, since they
                had tested only for products released into solution. They also recom-
                mended that further irradiations be done under basic rather than the
                neutral or slightly acidic conditions they had used, because the stored
                wastes are expected to be basic (alkaline).

                Page 14                                          GAO/RCED-91-34   Nuclear   Energy
.   Ap~ndx      I
    Paclflc Northweet Labomtorlee     Evaluation
    of Potential Fbnvxyanide   Exploeion

    A PNL official told us in May 1990 that the question of decomposition
    remains unresolved. Apparently, the experiments were terminated
    before definitive results could be obtained.

    3. “Determine the kinetic parameters of the CN- and NOireaction by
    both experiment and calculation. The effect of inert materials is espe-
    cially important and must be included in these studies. The information
    obtained from these studies would allow realistic conclusions to be made
    regarding the potential for rapid exothermic reactions in waste tanks
    containing ferrocyanide solids. In addition, the conditions for potentially
    hazardous reactions would be known and could be precluded by tank
    management practices.”

    PNL  researchers conducted a short series of experiments during the
    summer and early fall of 1988 on the reactions of ferrocyanides with
    air, sodium nitrate, sodium nitrite, and a synthetic waste mixture. The
    onset of reactions was measured in three ways. Two methods measured
    all reactions of the ferrocyanide and one measured small explosions.

    The temperatures at which reactions started ranged from
    4000Fahrenheit (F) to as much as 9900 F. The lowest temperature reac-
    tions occurred between the ferrocyanide and a 60-60 mixture of sodium
    nitrate and sodium nitrite, a low melting mixture (eutectic) that may be
    present in the tank wastes.

    In the small-scale explosion tests, ferrocyanide reactions started at
    about 6200 F with the 60-60 mixture. An actual explosion did not occur
    until the temperature reached 68@ F with sodium nitrate, 66@ F with
    sodium nitrite, and 64P F with the 60-60 mixture.

    Adding inert material raised the temperature at which an explosion
    occurred. With a mixture intended to simulate tank composition, the
    ignition was at about 7600 F.

    The work in 1988 was funded only for a very brief time at the end of a
    fiscal year and not enough funding or time was allowed to do a defini-
    tive project. As a result, this investigation did not include the possible
    effects of initiators or catalysts. The presence of diluents in the ferrocy-
    anide layers, if any, was also not determined.

    A May 1989 safety study test plan described work (involving PNL, West-
    inghouse Hanford Company, and Los Alamos National Laboratories)
    which is now scheduled for completion in February 1991. A PNL official

    Page 15                                           GAO/lKXD-91-34   Nuclear   Energy
Arm*       1
Pad& Nortlweot      Laboratorh’     Evaluation
of Potential Ferrocyanide    Explosion

told us that some of the laboratory work already is complete and that
some catalysts, notably nickel, iron, and EDTA, lower the exothermic
and explosive temperatures by l@ to 260 F. That official told us that
work concerning the important question of the kinetics of the ferrocya-
nide reaction still was not done and was not definitely scheduled to be
done so far as he knew.

4. “Obtain tank samples and conduct chemical analyses for soluble and
insoluble cyanides, cyanate, nitrate, fission products, and water

During 1986, a sampling program was carried out to obtain cores from
two of the tanks (lOl-TY and 103-TY) which may contain ferrocyanides.
However, the analyses of these cores apparently did not include tests
for cyanides or cyanate, In 1988, cores from these two tanks were ana-
lyzed for cyanide, which was found to be present largely in insoluble
form. However the identity of the cyanide precipitates involved was not

The 1989 Westinghouse memorandum noted that the ferrocyanide was
expected to be in the lower depths of the waste in any tanks where
unpumpable liquid remained. In this position, the moisture reduces the
probability of a reaction because it removes heat from the reactive
material. The memorandum also noted that the ferrocyanide was prob-
ably concentrated in thin layers in the tank solids. It stated that
although concentrations could be determined by taking core samples and
analyzing them, this procedure would be costly and time consuming, and
instead undiluted ferrocyanide would be used in experiments by PNL.

Apparently, there are no cores available from any other ferrocyanide
tanks. All of these tanks are scheduled for eventual sampling and anal-
ysis as part of the current waste characterization study.

6. “Obtain the temperature profile of the tanks to give information on
temperature maxima and on possible layering of solids.”

The 1989 Westinghouse memorandum compared the temperatures mea-
sured in the tanks with the temperatures required to initiate the ferro-
cyanide reaction and noted the large safety margin. The memorandum
also noted that concerns about temperature increases after stabilization
were not supported by experience to date because there had been no
apparent increase in temperature due to pumping liquid out of the

Page 16                                          GAO/RCED-91-34   Nuclear   Energy

.       ApPmdlxI
        of Potential Femoeyanlde Expluaion

        6. “Obtain and analyze the gamma profile to provide information on
        temperature maxima and on possible layering of solids.”

        No gamma profile has been taken.

        Page 17                                      GAO/RCED-Bl-&I   Nuclear   Energy
Appendix II

Report of the DOE Ad Hoc Task Force

              20    September     1990

                                                        cc:     Steve Cowan, EM-30
                                                                John Wagner, DOE-RL
                                                                Gary Bracken, DOE-RL

              To:          John Tseng
                           Office of Environmental     Restoration   and Waste Management

              From:        Tom Xress, Oak Ridge National Laboratory
                           Xamal Bandyopadhyay, Brookhaven National     Laboratory     kd
                           Paul d'Entremont,   Westinghouse Savannah RivytTany              F
                           * Scott Slezak,   Sandia National Laboratory
                           * Morris Reich, Brookhaven National Laboratory
              * Attended        the investigation   part time

                RISK OF A FERROCYANIDE
                                     EXPLOSIONIN THE HANFORDWASTETANK FARM

              Certain single-shell      tanks in the Hanford waste tank farms contain
              larqe quantities     of ferrocyanide     (Borsheim and Xirch).  This
              ferrocyanide   may contribute      to the formation of chemical mixtures
              that are explosive at elevated temperatures (Burger and Scheele,
              1990). A ferrocyanide        explosion is considered to be the Upper
              Bound accident during disposal of Hanford High-Level Wastes (J.
              Mishima et al.).       The report by Mishima et al. is the basis for
              the dose calculations       shown in the Environmental Impact Statement
               (EIS) for disposal of Hanford Wastes.
              During a recent audit, the General Accounting Office (GAO)
              expressad concern regarding the EIS dose calculations.      A GAO
              consultant,   George W. Hinman, calculated that the offsite   dose
              from a ferrocyanide   explosion could be up to two orders of
              magnitude higher than that shown in the EIS (Hinman).
              The DOEOffice of Environmental Restoration         and Waste Management
              formed a task team to investigate      this concern.    The team
              consistad of the authors of this memo. The charter of the task
              team was 1) to review Hinman's calculations        and explain the
              differences   between his calculations     and those in the EIS, 2) to
              make a qualitative     judgement a8 to which calculations     were most
              appropriate,    and 3) to recommend a program for-handling      the
              ferrocyanide    safety issue.

                        Page18                                           GAO/lZCEDBl-94NuclearXnergy

.                  Amendix    II

        Page 2
        20     September     1990

        The  task team conducted its review on 28-29 August 1990. The team
        reviewed    pertinent    documents and interviewed key personnel at DOE-
        Richland, Westinghouse Hanford Company (WHC), and Pacific
        Northwest Laboratories       (PNL). The team did not have the
        opportunity     to interview   Hinman.

        Hinman calculated   a higher offsite     dose than the EIS because he
        assumed that a higher fraction      (0.1 to 1.0) of the Cs-137 is
        carried into the air as fine, respirable        particles.    The EIS
        assumed only a small respirable      fraction   for   both Cs-137 and
        W-90, namely 0.000005.      With the higher Cs-137 fraction        assumed
        by Hinman, Ca-137 became the dominant contributor          to radiation
        dose. The EIS analysis showed Sr-90 as the primary dose
        contributor,   with a committed dose two orders of magnitude less
        than the dose calculated    by Hinman.
        The task team agrees    with Hinman that the respirable   fraction  of
        Cs-137 is likely   to be higher than assumed in the EIS because much
        of the Cs-137 in these tanks is in intimate     contact with the
        explosive.   But the team cannot recommend vhat fraction      should be
        used  because it is not aware of any data that bears on the issue.
        There are a number of factors that will tend to attenuate the
        dispersion  of respirable    aerosols that were not considered in the
        EIS analysis or in Hinman's analysis.
        The team believes that the risk of a ferrocyanide               explosion is
        low. In experimental work at PNL, the lowest temperature at which
        an exothermic reaction has been observed is 446 degrees F (Burger
        and Scheele, 1990). The highest temperature currently                  measured in
        a tank containing     ferrocyanide        is 135 degrees F (Borsheim and
        Xirch).      The team recognizes that neither of these temperatures
        can be considered limiting        values,      and the  team  recommends that
        further work continue to define the limiting               temperatures more
        accurately.      But, considering      the margin between these two
        temperatures,     the team believes the probability           of an explosion is
        low enough that the risk (probability             times consequence) is low.
        However, the team has no basis            at this   time to quantify the
        Therefore, the task team recommends that near-term efforts
        emphasize determining the probability  of an explosion.   The team
        recommends several key elements that should be included in this

                  Page19                                            GAO/RCED-9184NuclearEnergy

          AppendLr II

Page 3
20 Septenrber 1990

program. The team also recommends that better information       be
obtained on the fraction of respirable aerosols following      a
ferrocyanide  explosion.
Finally,    the task team recommends that plans be developed
expeditiously     for final disposal of these wastes.

A  eummary of the task team's recommendations follows.  Each of
these recommendations is discussed in more detail in the body of
the report.
l     Near term efforts    should be concentrated on experiments and
      investigations    to 1) determine the maximum temperature in a
      single-shell   tank and 2) the detonation temperature of
      ferrocyanide   mixtures that could cradibly  occur in a tank.
      The goal should be to define the probability    of an explosion.
l     The tanks of concern should be sampled to better characterize
      the wastes.   Sample data is needed for several reasons: 1) to
      determine credible ferrocyanide    mixtures, which is needed to
      estimate the minimum ignition   temperature,  2) to determine
      physical properties  of the waste that will help in estimating
      maximum temperatures in the waste, and 3) to guide
      experiments on aerosol generation.
l     Studies underway on the initiating mechanisms for an
      explosion (e.g. spark, impact) should be continued.
l     The possible formation of "hot spots" should be studied with
      the objective   of defining the probability of hot spot
      temperatures approaching the exothermic reaction temperatures
      of ferrocyanide   mixtures.
l     Studies should be conducted to determine if any other
      chemicals might form in the tanks that could cause exothermic
      reactions or explosions at temperatures lower than required
      for ferrocyanide  reactions.
0     Temperature monitoring techniques and/or    equipment need to be
      improved to reduce scatter and eliminate    spurious readings.
l     A formal action plan is needed for cases when the measured
      temperature in a ferrocyanide tank increases.

          Page20                                      GAO/RCED-9194NuclearEnergy
[Technical material on this
page and the following
pages of this letter has
                              Page 4
                              20 September 1990

                              l    Explosion   tests should be performed to measure the aerosol
                                   fraction,   using simulated wastes on a scale basis.
                              l    Long-term plans should be developed expeditiously      for   final
                                   disposal of these wastes.


                                    Page21                                       GAO/R-91-84       Nuclear   Energy

Appendix III

Major Contributors to This Report

                          Judy A. England-Joseph, Associate Director
Resources,                Robert E. Allen, Jr., Assistant Director
Community, and            Edward E. Young, Jr., Assignment Manager
Development Division,
Washington, D.C.

                          Leonard L. Dowd, Regional Manager Representative
Seattle Regional Office   Charles A. Sylvis, Evaluator-in-Charge
                          Dianne Whitman, Evaluator
                          Stanley G. Stenersen, Senior Report Editor
                          George W. Hinman, DSc., Consultant

(301950)                  Page 22                                      GAO/WED-91-34 Nuclear Energy
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