def fail_safe(temperature, neutrons_produced_per_second, threshold):
    """Assess and return status code for the reactor.

    :param temperature: value of the temperature in kelvin (integer or float)
    :param neutrons_produced_per_second: neutron flux (integer or float)
    :param threshold: threshold (integer or float)
    :return: str one of: 'LOW', 'NORMAL', 'DANGER'

    - `temperature * neutrons per second` < 90% of `threshold` == 'LOW'
    - `temperature * neutrons per second` +/- 10% of `threshold` == 'NORMAL'
    - `temperature * neutrons per second` is not in the above-stated ranges ==  'DANGER'
    """

    result = temperature * neutrons_produced_per_second

    if result < threshold * 0.9:
        return 'LOW'
    if 0.9 * threshold <= result <= 1.1 * threshold:
        return 'NORMAL'
    return 'DANGER'