[DNFSB
LETTERHEAD]
December 7, 2004
The Honorable Spencer Abraham
Secretary of Energy
1000 Independence Avenue, SW
Washington. DC 20585-1000
Dear Secretary Abraham:
On December 7, 2004, the Defense
Nuclear Facilities Safety Board (Board), in accordance with 42 U.S.C. § 2286a(a)(5),
unanimously approved Recommendation 2004-2, Active Confinement Systems,
which is enclosed
for your consideration. This
recommendation addresses the confinement of hazardous materials at defense
nuclear facilities in the Department of Energy (DOE) complex.
In order to assist you in
developing a response to this recommendation, the Board has enclosed a
technical report, DNFSB/TECH-34, Confinement of Radioactive Materials at Defense
Nuclear Facilities. This study compares the benefits
of employing a safety-related active confinement ventilation system to a policy
of relying only on a passive confinement system.
After your receipt of this recommendation
and as required by 42 U.S.C. §
2286d(a), the Board will promptly make
it available to the public. The Board
believes that the recommendation contains no information that is classified or
otherwise restricted. To the extent this
recommendation does not include information restricted by DOE under the Atomic
Energy Act of 1954, 42 U.S.C. §§
2161-68, as
amended, please arrange to have it promptly placed on file in your regional
public reading rooms. The Board will
also publish this recommendation in the Federal Register. The
Board will evaluate the Department of Energy response to this recommendation in
accordance with Board Policy Statement 1, Criteria for Judging the Adequacy of DOE Responses and
Implementation Plans for Board Recommendations.
Sincerely,
John T. Conway
Chairman
c: Mr. Mark B. Whitaker, Jr.
RECOMMENDATION
2004-2 TO THE SECRETARY OF ENERGY
Pursuant
to 42 U.S.C. §
2286a(a)(5),
Atomic
Energy Act of 1954, As Amended
Dated: December 7, 2004
There is a long-standing safety
practice in the design, construction, and operation of nuclear facilities to
build-in and maintain structures, systems, and components that contain or confine
radioactive materials. The Department of
Energy (DOE) establishes requirements to ensure such containment or confinement.
In the hierarchy of safety controls,
passive design features are preferred over active systems; however, controls
must be capable of performing their intended function. Passive confinement systems are not
necessarily capable of containing hazardous materials with confidence because
they allow a quantity of unfiltered air contaminated with radioactive material
to be released from an operating nuclear facility following certain accident
scenarios. Safety related active
confinement ventilation systems will continue to function during an accident,
thereby ensuring that radioactive material is captured by filters before it can
be released into the environment.
The enclosed technical report,
DNFSB/TECH-34, Confinement
of Radioactive Materials at Defense Nuclear Facilities,
compares the
benefits of including a safety-related active confinement ventilation system to
those of relying only on a passive confinement system. This technical report illustrates that using
only a passive confinement system for an existing or new defense nuclear
processing facility would not account for many safety considerations such as post-accident
monitoring and response, and may result in the release of an undeterminable amount
of radioactive materials, the consequences of which could approach that of the unmitigated
scenarios.
The Defense Nuclear Facilities
Safety Board (Board) has advised DOE in various ways during the past decade
regarding the need to pay increased attention to the design and operational reliability
of the confinement ventilation systems at defense nuclear facilities. These Board efforts include transmittal of a
technical report on May 31, 1995, Overview of Ventilation Systems at Selected DOE
Plutonium Processing and Handling Facilities, a letter to the Deputy Secretary
of Energy dated July 8, 1999, and Recommendation 2000-2, Configuration Management,
Vital Safety Systems, on
March 8, 2000.
This advice has helped DOE improve the reliability
of its confinement ventilation systems. However, DOE requirements have become less prescriptive
during the last decade as DOE Order 6430.1A, General Design Criteria
Manual, was
replaced with DOE Order 420.1, Facility Safety, and its subsequent revisions. Furthermore, it has become apparent that the Board’s
advice on confinement systems is not being rigorously pursued as evidenced by
the following:
A number of existing facilities
(including the TA-55 Plutonium Facility, the Device Assembly Facility, and the
Hanford Evaporator) rely on passive or non-safety related confinement systems. More importantly, designs for proposed
facilities (including Chemistry and Metallurgy Research Replacement Facility
and the Salt Waste Processing Facility) are based on the same passive
confinement concept and use an assumed quantitative value for the building leak
path factor as a design criterion.
These examples illustrate two
primary concerns. First, a reliance on
calculations that do not appropriately account for large uncertainties is not
defensible. These analytically
determined building leak path factors are based on a combination of several
computer programs that were not specifically designed for this purpose. Furthermore, it is generally impossible for
these programs to model the true conditions of a real accident because of the
uncertain behavior of the workers and emergency crews responding to the event.
Second, these examples represent
a fundamental change in DOE’s approach to protection of the public near defense
nuclear facilities. DOE appears to be
using the evaluation guideline of 25 rem exposure at the site boundary as
a design criterion and an allowable dose to the public. This is contrary to the Board’s July 8, 1999
letter to the Deputy Secretary of Energy that states “the 25 rem evaluation
guideline is not to be treated as a design acceptance criterion nor as a justification
for nullifying the general design criteria relative to defense-in-depth safety measures.”
It is also contrary to DOE-STD-3009 that
states that the 25 rem evaluation guideline “is not to be treated as a design
acceptance criterion.” However, the
Board continues to see 25 rem at the site boundary used as an acceptance
criterion for the performance of confinement systems. The Board is concerned that in these examples
DOE and its contractors are underestimating the significance of the performance
requirements for a confinement ventilation system and are relying on
questionable calculations of offsite doses to evaluate performance. The Board reiterates that the 25 rem evaluation
guideline is solely to be used for guidance for the classification of safety
controls, and not as an acceptable dose to the public for the purpose of
designing or operating defense nuclear facilities.
Notwithstanding the concerns
discussed above, DOE continues to pursue a passive confinement approach in the
design of some new nuclear facilities that have the potential for a radiological
release. The Board recognizes that DOE’s
defense nuclear complex is comprised of a wide variety of nuclear facilities
with an equally diverse range of materials, forms, activities, and proximities
to the public. For this reason, it is
difficult to prescribe a single, broadly-applicable design requirement. However, in light of the examples discussed
above, the Board believes a more prescriptive design requirement is needed.
The Board further recognizes
that certain Hazard Category 2 and 3 defense nuclear facilities may not benefit
significantly from an active confinement ventilation system. An example would be a facility that stores
radioactive material in protected, safety-class containers. Other examples may be certain tritium
facilities, outside storage locations, burial grounds, or facilities with
planned declining nuclear material inventories and scheduled for
decommissioning in the near future. This
recommendation is not meant to require an active confinement ventilation system
in all such cases.
Therefore,
the Board recommends that DOE:
a)
the
confinement strategy described above is implemented, and
b)
the
25 rem evaluation guideline is used solely for classification of safety
controls.
Section 42 U.S.C. § 2286d(e) provides authority to the
Secretary of Energy to “implement any such Recommendation (or part of any such
Recommendation) before, on, or after the date on which the Secretary of Energy
transmits the implementation plan to the Board under this subsection.” The Board suggests that the Secretary of
Energy consider taking action on Item 4 above in parallel with the development
of an Implementation Plan for this Recommendation.
In addition, the Board’s
Recommendation 2004-1, Oversight
of Complex, High-Hazard Nuclear Operations, addresses the need for
complex-wide consistency in the application of DOE requirements and
expectations. The Board expects the
mechanisms established in response to Recommendation 2004-1 would likewise ensure
consistent, conservative implementation of the confinement requirement provided
here.
John T. Conway, Chairman